Science of Synthesis: Houben-Weyl Methods of Molecular Transformations  Vol. 6 -  - E-Book

Science of Synthesis: Houben-Weyl Methods of Molecular Transformations Vol. 6 E-Book

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Science of Synthesis provides a critical review of the synthetic methodology developed from the early 1800s to date for the entire field of organic and organometallic chemistry. As the only resource providing full-text descriptions of organic transformations and synthetic methods as well as experimental procedures, Science of Synthesis is therefore a unique chemical information tool. Over 1000 world-renowned experts have chosen the most important molecular transformations for a class of organic compounds and elaborated on their scope and limitations. The systematic, logical and consistent organization of the synthetic methods for each functional group enables users to quickly find out which methods are useful for a particular synthesis and which are not. Effective and practical experimental procedures can be implemented quickly and easily in the lab.// The content of this e-book was originally published in December 2004.

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Science of Synthesis

Science of Synthesis is the authoritative and comprehensive reference work for the entire field of organic and organometallic synthesis.

Science of Synthesis presents the important synthetic methods for all classes of compounds and includes:

Methods critically evaluated by leading scientists

Background information and detailed experimental procedures

Schemes and tables which illustrate the reaction scope

Preface

As our understanding of the natural world increases, we begin to understand complex phenomena at molecular levels. This level of understanding allows for the design of molecular entities for functions ranging from material science to biology. Such design requires synthesis and, as the structures increase in complexity as a necessity for specificity, puts increasing demands on the level of sophistication of the synthetic methods. Such needs stimulate the improvement of existing methods and, more importantly, the development of new methods. As scientists confront the synthetic problems posed by the molecular targets, they require access to a source of reliable synthetic information. Thus, the need for a new, comprehensive, and critical treatment of synthetic chemistry has become apparent. To meet this challenge, an entirely new edition of the esteemed reference work Houben–Weyl Methods of Organic Chemistry will be published starting in the year 2000.

To reflect the new broader need and focus, this new edition has a new title, Science of Synthesis, Houben–Weyl Methods of Molecular Transformations. Science of Synthesis will benefit from more than 90 years of experience and will continue the tradition of excellence in publishing synthetic chemistry reference works. Science of Synthesis will be a balanced and critical reference work produced by the collaborative efforts of chemists, from both industry and academia, selected by the editorial board. All published results from journals, books, and patent literature from the early 1800s until the year of publication will be considered by our authors, who are among the leading experts in their field. The 48 volumes of Science of Synthesis will provide chemists with the most reliable methods to solve their synthesis problems. Science of Synthesis will be updated periodically and will become a prime source of information for chemists in the 21st century.

Science of Synthesis will be organized in a logical hierarchical system based on the target molecule to be synthesized. The critical coverage of methods will be supported by information intended to help the user choose the most suitable method for their application, thus providing a strong foundation from which to develop a successful synthetic route. Within each category of product, illuminating background information such as history, nomenclature, structure, stability, reactivity, properties, safety, and environmental aspects will be discussed along with a detailed selection of reliable methods. Each method and variation will be accompanied by reaction schemes, tables of examples, experimental procedures, and a background discussion of the scope and limitations of the reaction described.

The policy of the editorial board is to make Science of Synthesis the ultimate tool for the synthetic chemist in the 21st century.

We would like to thank all of our authors for submitting contributions of such outstanding quality, and, also for the dedication and commitment they have shown throughout the entire editorial process.

October 2000

The Editorial Board D. Bellus (Basel, Switzerland) E. N. Jacobsen (Cambridge, USA) S. V. Ley (Cambridge, UK) R. Noyori (Nagoya, Japan) M. Regitz (Kaiserslautern, Germany) P. J. Reider (New Jersey, USA) E. Schaumann (Clausthal-Zellerfeld, Germany) I. Shinkai (Tsukuba, Japan) E. J. Thomas (Manchester, UK) B. M. Trost (Stanford, USA)

Volume Editor’s Preface

During the planning of this volume of Science of Synthesis on boron chemistry, more and more virtual sections (finally 41) and pages became necessary, and it became evident that boron had become an essential element in modern synthetic chemistry. Originally, Roland Köster, the editor of the three most valuable Houben-Weyl volumes on “Organo-borverbindungen”, had already planned an additional section on synthetic applications in 1982. It took more than 22 years to plan an entirely new volume on this particular topic, by now in the new series of Science of Synthesis. The authors originate from many different countries and research fields, thus representing the modern scientific community. In this way, it was possible to report on a large number of classical and actual synthetic developments, as well as potential applications, and to cover a broad field of topics ranging from asymmetric catalysis, over stereoselective syntheses of biologically active compounds, to polymeric organic materials with nonlinear optical properties. We have, however, excluded two special sections: methyleneboranes and small ring boranes. The chemistry and properties of these classes of compounds deserve much interest in terms of chemical bonding and new mechanistical reaction paths; however, synthetic applications are not foreseeable.

A large section was devoted to trialkylboranes, and this section was chosen as a key part for the description of the selective conversion of carbon-boron bonds, in order to keep a collection of related synthetic methods together and therefore make it easier to find and compare these methods. Analogous to Houben-Weyl, Science of Synthesis is also “product based”. This means that both reactive intermediates and catalysts are treated in the “applications in organic synthesis” parts of all sections. Additionally, all authors have in general tried to present a practical and reliable collection of symmetric and asymmetric variants of synthetic methods.

After most of the authors had already signed, I was grateful to Don Matteson for joining me as a co-editor when the workload was increasing. I would like to thank Roland Koster for his encouragement and confidence in continuing and extending his original work and - last but not least - his valuable, enormous collection of articles on boron chemistry. I would also like to thank Guido F. Herrmann and Fiona Shortt de Hernandez for their assistance during the development stages of the volume, and especially Karen Muirhead and Leigh Murray for their professional, efficient and friendly assistance, especially during the last critical weeks. My thanks are extended to my research group for reading early drafts of the chapters and tolerating my absence from their labs as well as my continuously closed door. Finally I am really grateful for the acceptance of my family for my almost complete absence in the Harz mountains during the week and on many weekends over a long time period. Being published on December 23, this volume will remain as a great memory and a lasting Christmas present for me.

Clausthal, December 2004

Volume Editor Dieter E. Kaufmann

Volume 6: Boron Compounds

Preface

Volume Editor’s Preface

Table of Contents

Introduction

D. E. Kaufmann

6.1 Product Class 1: Boron Compounds

6.1.1 Product Subclass 1: Hydroboranes

D. S. Matteson

6.1.2 Product Subclass 2: Borohydrides

G Chen

6.1.3 Product Subclass 3: Diborane(4) Compounds

T. B. Marder

6.1.4 Product Subclass 4: Metalloboranes

H. Nöth

6.1.5 Product Subclass 5: Haloboranes

D. S. Matteson

6.1.6 Product Subclass 6: Haloborates

B. Schilling and D. E. Kaufmann

6.1.7 Product Subclass 7: Hydroxyboranes

N. Miyaura

6.1.8 Product Subclass 8: Boroxanes

M. Periasamy, M. Seenivasaperumal, and S. Sivakumar

6.1.9 Product Subclass 9: Acyloxyboranes

M. Periasamy, M. N. Reddy, and N. S. Kumar

6.1.10 Product Subclass 10: Vinyloxyboranes

C. Gennari, S. Ceccarelli, and U. Piarulli

6.1.11 Product Subclass 11: Aryloxy- and Alkoxyboranes (Including Protecting Groups)

K. Ishihara and H. Yamamoto

6.1.12 Product Subclass 12: Aryloxy- and Alkoxyborates

K. Ishihara and H. Yamamoto

6.1.13 Product Subclass 13: Peroxyboranes

K. Ishihara and H. Yamamoto

6.1.14 Product Subclass 14: Sulfanyl- and Selanylboranes

C. Habben and D. E. Kaufmann

6.1.15 Product Subclass 15: Aminoboranes and Borane-Amine Complexes

B. Carboni and F. Carreaux

6.1.16 Product Subclass 16: Phosphinoboranes and Borane-Phosphine Complexes

A. C. Gaumont and B. Carboni

6.1.17 Product Subclass 17: α-Metalloalkylboranes

Bakthan Singaram

6.1.18 Product Subclass 18: Cyanoboranes

D. Gabel and M. B. El-Zaria

6.1.19 Product Subclass 19: Carboxyboranes and Related Derivatives

D. Gabel and M. B. El-Zaria

6.1.20 Product Subclass 20: α-Haloalkylboronates

D. S. Matteson

6.1.21 Product Subclass 21: α-Alkoxyalkyl-, α-Sulfanylalkyl-, and α-Aminoalkylboronates

D. S. Matteson

6.1.22 Product Subclass 22: α-Phosphinoalkylboranes

D. S. Matteson

6.1.23 Product Subclass 23: Alk-1-ynylboranes and Alkyn-1-ylboronates

D. E. Kaufmann and N. Öcal

6.1.24 Product Subclass 24: Borylketenes

D Gabel

6.1.25 Product Subclass 25: Allenylboranes

D. E. Kaufmann and C. Burmester

6.1.26 Product Subclass 26: Aryl- and Hetarylboranes

N. Miyaura

6.1.27 Product Subclass 27: Dienylboranes

K. Albrecht and D. E. Kaufmann

6.1.28 Product Subclass 28: Vinylboranes

M. Vaultier and G. Alcaraz

6.1.29 Product Subclass 29: α-Boryl Carbonyl Compounds

H. Abu Ali, V. M. Dembitsky, and M. Srebnik

6.1.30 Product Subclass 30: β-Haloalkylboranes

H. Abu Ali, V. M. Dembitsky, and M. Srebnik

6.1.31 Product Subclass 31: β-Alkoxyalkyl-, β-Sulfanylalkyl-, and β-Aminoalkylboranes

H. Abu Ali, V. M. Dembitsky, and M. Srebnik

6.1.32 Product Subclass 32: β-Silylalkyl- and β-Stannylalkylboranes

P. J. Murphy

6.1.33 Product Subclass 33: Propargylboranes

D. E. Kaufmann and C. Burmester

6.1.34 Product Subclass 34: Benzylboranes and Benzylboronates

M. Zaidlewicz and J. Meller

6.1.35 Product Subclass 35: Allylboranes

Y. Bubnov

6.1.36 Product Subclass 36: β-Boryl Carbonyl Compounds

D. S. Matteson

6.1.37 Product Subclass 37: γ-Haloalkylboranes

H. Abu Ali, V. M. Dembitsky, and M. Srebnik

6.1.38 Product Subclass 38: Trialkylboranes

M. Zaidlewicz and M. Krzeminski

6.1.39 Product Subclass 39: Tetraaryl- and Tetraalkylborates and Related Organometallic Compounds

D. E. Kaufmann and M. Köster

6.1.40 Product Subclass 40: Carboranes and Metallacarboranes

F. Teixidor and C. Viñas

6.1.41 Product Subclass 41: Boron-Containing Polymers

D. Gabel

Keyword Index

Author Index

Abbreviations

Table of Contents

Introduction

D. E. Kaufmann

Introduction

6.1 Product Class 1: Boron Compounds

6.1.1 Product Subclass 1: Hydroboranes

D. S. Matteson

6.1.1 Product Subclass 1: Hydroboranes

Synthesis of Product Subclass 1

6.1.1.1 Diborane and Borane–Ether Complexes

6.1.1.1.1 Method 1: From Tetrahydroborates with Lewis Acids

6.1.1.1.1.1 Variation 1: From Tetrahydroborate with Protic Acids

6.1.1.1.1.2 Variation 2: From Tetrahydroborates with Iodine

6.1.1.1.1.3 Variation 3: Introduction of Isotopic Labels via Labeled Boranes

6.1.1.2 Substituted Tricoordinate Boranes

6.1.1.2.1 Method 1: Halohydroboranes from Boron Trichloride and Trialkylsilanes

6.1.1.2.2 Method 2: Oxyhydroboranes from Diborane and Hydroxy Compounds

6.1.1.3 Asymmetric Acyloxyboranes

6.1.1.4 Sulfanylhydroboranes

6.1.1.5 Aminohydroboranes

6.1.1.6 Borazines

6.1.1.7 Alkylhydroboranes by Hydroboration

6.1.1.7.1 Method 1: Synthesis by Hydroboration

6.1.1.7.2 Method 2: Asymmetric Alkylhydroboranes

6.1.1.8 Alkylhydroboranes by Other Routes

6.1.1.8.1 Method 1: Alkylboranes

6.1.1.8.1.1 Variation 1: Synthesis from Alkylborohydrides

6.1.1.8.1.2 Variation 2: Synthesis from Alkylheteroboranes

6.1.1.8.1.3 Variation 3: Synthesis from Alkyldichloroboranes

6.1.1.9 Hydroborane–Lewis Base Complexes

6.1.1.9.1 Method 1: Borane–Dialkyl Sulfides

6.1.1.9.2 Method 2: Borane–Amines

6.1.1.9.2.1 Variation 1: Hydroboration with Borane–Amines

6.1.1.9.2.2 Variation 2: Reductions with Borane–Amines

6.1.1.9.2.3 Variation 3: Group Substitution within Borane–Amines

6.1.1.10 Diaminoboronium Cations

6.1.1.11 Borane–Phosphines

6.1.1.12 Borane–Carbonyl

Applications of Product Subclass 1 in Organic Synthesis

6.1.1.13 Diborane

6.1.1.14 Halohydroboranes

6.1.1.15 Oxyhydroboranes

6.1.1.15.1 Method 1: Hydroboration

6.1.1.15.2 Method 2: Reductions with Dioxyboranes

6.1.1.16 Catalytic Reactions of Oxyhydroboranes

6.1.1.16.1 Method 1: Replacement of Hydrogen or Halogen Atoms by Boron

6.1.1.16.1.1 Variation 1: Replacement of Hydrogen

6.1.1.16.1.2 Variation 2: Replacement of Halogen

6.1.1.16.2 Method 2: Catalytic Reductions with Asymmetric Oxazaborolidines

6.1.1.16.3 Method 3: Catalytic Reductions with Transition-Metal Catalysts

6.1.1.16.4 Method 4: Catalytic Asymmetric Hydroborations

6.1.1.16.4.1 Variation 1: By Rhodium and Iridium Catalysts

6.1.1.16.4.2 Variation 2: By Palladium, Cobalt, and Nickel Catalysts

6.1.1.16.4.3 Variation 3: By Lanthanide and Early Transition Metal Catalysts

6.1.1.16.5 Method 5: Catalytic Hydroboration of Alkynes

6.1.1.16.6 Method 6: Hydroboration of Vinylarenes

6.1.2 Product Subclass 2: Borohydrides

G. Chen

6.1.2 Product Subclass 2: Borohydrides

Synthesis of Product Subclass 2

6.1.2.1 Method 1: Preparation of Unsubstituted Borohydrides (Tetrahydroborates)

6.1.2.2 Method 2: Preparation of Cyanoborohydrides

6.1.2.3 Method 3: Preparation of Alkylborohydrides

6.1.2.4 Method 4: Preparation of Alkylalkoxy-, Trialkoxy-, and Acyloxyborohydrides

6.1.2.5 Method 5: Preparation of Alkylaminoborohydrides

6.1.2.5.1 Variation 1: Preparation of Monoalkylaminoborohydrides

6.1.2.5.2 Variation 2: Preparation of Bis- and Tris(pyrazolyl)borohydrides

Applications of Product Subclass 2 in Organic Synthesis

6.1.2.6 Method 6: Reductive Cleavage of Carbon-Heteroatom Bonds

6.1.2.6.1 Variation 1: Reductive Cleavage of C-O Bonds

6.1.2.6.2 Variation 2: Reductive Cleavage of C-S Bonds

6.1.2.6.3 Variation 3: Reductive Cleavage of C-N Bonds

6.1.2.6.4 Variation 4: Reduction of Halides to Hydrocarbons

6.1.2.7 Method 7: Reductions of C=O Bonds

6.1.2.7.1 Variation 1: Reduction of Aldehydes and Ketones to Hydrocarbons

6.1.2.7.2 Variation 2: Reduction of Aldehydes and Ketones to Alcohols

6.1.2.7.3 Variation 3: Diastereoselective Reduction of Ketones to Alcohols

6.1.2.7.4 Variation 4: Enantioselective Reduction of Prochiral Ketones to Chiral Alcohols

6.1.2.7.5 Variation 5: Reductions of Carboxylic Acids and Derivatives

6.1.2.8 Method 8: Reductions of C=N Bonds

6.1.2.8.1 Variation 1: Reduction of Imines and Derivatives

6.1.2.8.2 Variation 2: Reductive Amination in Solution Phase

6.1.2.8.3 Variation 3: Solid-Phase Reductive Amination

6.1.2.9 Method 9: Reduction of Nitriles

6.1.2.10 Method 10: Reduction of Azides

6.1.2.11 Method 11: Reduction of Nitro Compounds

6.1.3 Product Subclass 3: Diborane(4) Compounds

T.B. Marder

6.1.3 Product Subclass 3: Diborane(4) Compounds

Synthesis of Product Subclass 3

6.1.3.1 Method 1: Reductive Coupling of Bis(dimethylamino)(halo)boranes

6.1.3.2 Method 2: Reaction of Tetrakis(dimethylamino)diborane(4) with Alcohols and Thiols

6.1.3.2.1 Variation 1: Reaction with Chiral 1,2-Diols

6.1.3.2.2 Variation 2: Reaction with Thiols

Applications of Product Subclass 3 in Organic Synthesis

6.1.3.3 Method 3: Oxidative Addition of the B—B Bond to Metal Centers

6.1.3.4 Method 4: Catalyzed Diboration of α,β-Unsaturated Ketones

6.1.3.4.1 Variation 1: Using (η2-Ethene)bis(triphenylphosphine)platinum(0)

6.1.3.4.2 Variation 2: Using Tetrakis(triphenylphosphine)platinum(0)

6.1.3.4.3 Variation 3: Using Bis(phenylimino)acenaphthene(dimethylfumarate)- platinum(0)

6.1.3.4.4 Variation 4: Using Copper(I) Trifluoromethanesulfonate/Tributylphosphine

6.1.3.4.5 Variation 5: Using Stoichiometric Copper(I) Chloride/Lithium Chloride/Potassium Acetate

6.1.3.4.6 Variation 6: Using Chlorotris(triphenylphosphine)rhodium(I)

6.1.3.5 Method 5: Platinum-Catalyzed Diboration of Alkynes and Diynes

6.1.3.5.1 Variation 1: Diboration of Alkynes Using Tetrakis(triphenylphosphine)- platinum(0)

6.1.3.5.2 Variation 2: Diboration of Alkynes and Diynes Using (η2-Ethene)bis(triphenylphosphine)platinum(0)

6.1.3.5.3 Variation 3: Diboration of Alkynes Using Tris(norbornene)platinum/Diphenyl(2-tolyl)phosphine

6.1.3.6 Method 6: Platinum- or Palladium-catalyzed Diboration of Dienes

6.1.3.6.1 Variation 1: Tetrakis(triphenylphosphine)platinum(0)- and Bis(dibenzyl-ideneacetone)platinum-Catalyzed Diboration of 1,3-Dienes

6.1.3.6.2 Variation 2: Tetrakis(triphenylphosphine)platinum(0)- and Bis(dibenzylideneacetone) platinum-Catalyzed Diboration of 1,2-Dienes

6.1.3.6.3 Variation 3: Catalyzed Diboration of 1,2-Dienes Using Bis(dibenzylideneacetone) palladium in the Presence of Organic Iodides

6.1.3.7 Method 7: Catalyzed Diboration of Alkenes

6.1.3.7.1 Variation 1: Using Phosphine-Free Platinum(0)

6.1.3.7.2 Variation 2: Using Phosphine-Free Platinum(0) and Chiral Diborane(4)

6.1.3.7.3 Variation 3: Using a Bis(diphenylphosphino)methane-Rhodium-η6-Bis(catecholato)borate Catalyst

6.1.3.7.4 Variation 4: Rhodium-Catalyzed Asymmetric Diboration of Alkenes

6.1.3.7.5 Variation 5: Diboration of Methylenecyclopropanes Using Tetrakis(triphenylphosphine)platinum(0) or Bis(dibenzylideneacetone)platinum

6.1.4 Product Subclass 4: Metalloboranes

H. Nöth

6.1.4 Product Subclass 4: Metalloboranes

Synthesis of Product Subclass 4

6.1.4.1 Method 1: Synthesis of Silylboranes

6.1.4.1.1 Variation 1: Substitution Reactions

6.1.4.1.2 Variation 2: Insertion Reactions

6.1.4.1.3 Variation 3: Co-dehalogenation Reactions

6.1.4.1.4 Variation 4: Discharge Reactions

6.1.4.2 Method 2: Synthesis of Germylboranes

6.1.4.3 Method 3: Synthesis of Stannylboranes

6.1.4.4 Method 4: Synthesis of Plumbylboranes

6.1.4.5 Method 5: Synthesis of Silyl-, Germyl-, Stannyl-, and Plumbylborates and Related Compounds

6.1.4.5.1 Variation 1: By Addition of a Borane to Metal Silanides or Stannanides

6.1.4.5.2 Variation 2: Silyl-, Stannyl-, and Germylborates by Substitution Reactions

6.1.4.5.3 Variation 3: B-Si Bond Formation via a Li-B Intermediate

Applications of Product Subclass 4 in Organic Synthesis

6.1.4.6 Method 6: Sila- and Stannaboration with Silyl- and Stannylboranes

6.1.4.6.1 Variation 1: Alkenes

6.1.4.6.2 Variation 2: Allenes

6.1.4.6.3 Variation 3: 1,3-Dienes

6.1.4.6.4 Variation 4: Reaction of 1-Boryl-4-silylbut-2-enes with Aldehydes

6.1.4.6.5 Variation 5: Silylboration of Alkynes

6.1.4.6.6 Variation 6: Stannaboration of Alkynes

6.1.4.7 Method 7: Reaction of Alkynes with Silyl- and Stannylborates

6.1.4.8 Method 8: Transition Metal Borations

6.1.4.9 Method 9: Transition Metal Borides

6.1.5 Product Subclass 5: Haloboranes

D. S. Matteson

6.1.5 Product Subclass 5: Haloboranes

Synthesis of Product Subclass 5

6.1.5.1 Boron Trihalides

6.1.5.1.1 Method 1: Synthesis of Boron Trifluoride

6.1.5.1.2 Method 2: Synthesis of Boron Trifluoride–Diethyl Ether Complex

6.1.5.1.3 Method 3: Synthesis of Boron Trichloride

6.1.5.1.4 Method 4: Synthesis of Boron Tribromide

6.1.5.1.5 Method 5: Synthesis of Boron Triiodide

6.1.5.2 Halo(oxy)boranes

6.1.5.2.1 Method 1: Synthesis of Halo(dioxy)- and Dihalo(oxy)boranes

6.1.5.2.1.1 Variation 1: Synthesis of Alkoxy(chloro)boranes

6.1.5.2.2 Method 2: Synthesis of Alkyl- and Aryl(halo)(oxy)boranes

6.1.5.2.2.1 Variation 1: From Alkoxy Metals

6.1.5.2.2.2 Variation 2: By Ligand Exchange between Two Boron Components

6.1.5.3 Amino(halo)boranes

6.1.5.3.1 Method 1: Synthesis of Amino(dihalo)boranes and Diamino(halo)boranes

6.1.5.3.1.1 Variation 1: Synthesis of Amino(dihalo)boranes

6.1.5.3.1.2 Variation 2: Synthesis of Diamino(halo)boranes

6.1.5.3.2 Method 2: Synthesis of Alkyl- and Aryl(amino)(halo)boranes and Related Compounds

6.1.5.3.2.1 Variation 1: Synthesis of Diamino(chloro)boronium Chlorides

6.1.5.4 Alkyl- and Aryl(halo)boranes

6.1.5.4.1 Method 1: Synthesis of Alkyl- and Aryl(fluoro)boranes

6.1.5.4.2 Method 2: Synthesis of Alkyl- and Aryl(chloro)boranes

6.1.5.4.2.1 Variation 1: Hydroboration of Alkenes

6.1.5.4.2.2 Variation 2: By Conversion of B-H Bonds into B-Cl Bonds

6.1.5.4.2.3 Variation 3: By Replacement of B-Cl Bonds by B-C Bonds

6.1.5.4.2.4 Variation 4: By Addition to Alkynes

6.1.5.4.2.5 Variation 5: By Metal Replacement

6.1.5.4.2.6 Variation 6: By Conversion of B-O Bonds into B-Cl Bonds

6.1.5.4.2.7 Variation 7: By Conversion of B-F Bonds into B-Cl Bonds

6.1.5.4.3 Method 3: Synthesis of Alkyl- and Aryl(bromo)boranes and Alkyl- and Aryl(iodo)boranes

6.1.5.4.3.1 Variation 1: From Alkenes

6.1.5.4.3.2 Variation 2: From Acetylenes

6.1.5.4.3.3 Variation 3: Using Organometallic Reagents

Applications of Product Subclass 5 in Organic Synthesis

6.1.5.5 Boron Trifluoride

6.1.5.5.1 Method 1: Aldol–Grob Reaction

6.1.5.5.2 Method 2: Friedel–Crafts Reactions

6.1.5.6 Boron Trifluoride–Diethyl Ether Complex and Its Derivatives

6.1.5.6.1 Method 1: Reductions of Epoxides

6.1.5.6.2 Method 2: Complexes with Organocopper Compounds

6.1.5.6.3 Method 3: Organolithium Compounds

6.1.5.6.4 Method 4: Boron Trifluoride–Acetic Acid Complex

6.1.5.6.5 Method 5: Difluoroboryl Methanesulfonate

6.1.5.7 Boron Trichloride

6.1.5.7.1 Method 1: Detritylation

6.1.5.7.2 Method 2: Condensation of a Ketone with a Silylated Enediol

6.1.5.7.3 Method 3: Reactions Involving Aldehydes

6.1.5.7.3.1 Variation 1: Conversion of Aromatic Aldehydes into Aryl(dichloro)methanes

6.1.5.7.3.2 Variation 2: Condensation of Aromatic Aldehydes with Styrenes

6.1.5.7.3.3 Variation 3: Condensation of Aromatic Aldehydes with Arylacetylenes

6.1.5.7.4 Method 4: Diels–Alder Reactions

6.1.5.8 Boron Tribromide

6.1.5.8.1 Method 1: Cleavage of C-O Bonds

6.1.5.8.2 Method 2: Boron Demetalations

6.1.5.9 Boron Triiodide

6.1.5.10 Boron Triiodide–N,N-Diethylaniline Complex

6.1.5.11 Halo(oxy)boranes

6.1.5.11.1 Method 1: Reaction with Allyllithiums Followed by Alcohols or Aldehydes

6.1.5.11.2 Method 2: Alkenylation by Replacement of Zirconium

6.1.5.12 Amino(halo)boranes

6.1.5.12.1 Method 1: Preparation of Boron Heterocycles Using Amino(dihalo)boranes

6.1.5.12.2 Method 2: Using Diamino(halo)boranes

6.1.5.13 Alkyl- and Aryl(chloro)boranes

6.1.5.13.1 Method 1: Secondary Amine Formation Using Alkyl(chloro)boranes

6.1.5.13.2 Method 2: Reduction of Ketones to Alcohols

6.1.5.13.3 Method 3: Formation of Enolates from Ketones

6.1.5.13.4 Methods 4: Miscellaneous Applications

6.1.5.14 Alkyl- and Aryl(bromo)boranes and Alkyl- and Aryl(iodo)boranes

6.1.6 Product Subclass 6: Haloborates

B. Schilling and D. E. Kaufmann

6.1.6 Product Subclass 6: Haloborates

Synthesis of Product Subclass 6

6.1.6.1 Method 1: Destannylation of Organostannanes

6.1.6.2 Method 2: Fluorination of Organoboronic Acids and Esters

6.1.6.3 Method 3: Fluorination of Intermediate Organoboronic Acids and Esters

6.1.6.3.1 Variation 1: From Organolithium and Grignard Reagents

6.1.6.3.2 Variation 2: From Alkynes

Applications of Product Subclass 6 in Organic Synthesis

6.1.6.4 Method 4: Cross-Coupling Reactions of Potassium Aryltrifluoroborates

6.1.6.4.1 Variation 1: Addition to Aldehydes and Enones

6.1.6.4.2 Variation 2: With Arenediazonium Tetrafluoroborates

6.1.6.4.3 Variation 3: With Diaryliodonium Salts

6.1.6.5 Method 5: Substitution Using Inorganic Tetrahaloborates

6.1.6.5.1 Variation 1: Nucleophilic Substitution Reactions

6.1.6.5.2 Variation 2: Regioselective Fluorination Using Selectfluor

6.1.6.6 Method 6: Release of Difluoro(organo)boranes from Potassium Trifluoro(organo)borates

6.1.6.7 Method 7: Addition of Potassium Allyltrifluoroborates to Aldehydes and Ketones

6.1.6.8 Method 8: Addition Reactions Using Inorganic Tetrahaloborates (The Balz–Schiemann Reaction)

6.1.7 Product Subclass 7: Hydroxyboranes

N. Miyaura

6.1.7 Product Subclass 7: Hydroxyboranes

Synthesis of Product Subclass 7

6.1.7.1 Method 1: Direct Borylation of Alkanes and Arenes

6.1.7.2 Method 2: Transmetalation

6.1.7.2.1 Variation 1: Via Magnesium and Lithium Reagents

6.1.7.2.2 Variation 2: Via Other Metal Reagents

6.1.7.3 Method 3: Borylation of Aryl, Vinyl, and Allyl Halides

6.1.7.3.1 Variation 1: By Palladium-Catalyzed Coupling of Diboranes

6.1.7.3.2 Variation 2: By Palladium-Catalyzed Coupling of 1,3,2-Dioxaborolanes

6.1.7.4 Method 4: Hydroboration of Alkenes and Alkynes

6.1.7.4.1 Variation 1: Uncatalyzed Hydroboration

6.1.7.4.2 Variation 2: Catalyzed Hydroboration

6.1.7.5 Method 5: Diboration of Alkenes and Alkynes

6.1.7.5.1 Variation 1: Uncatalyzed Diboration

6.1.7.5.2 Variation 2: Catalyzed Diboration

6.1.7.6 Methods 6: Additional Methods

Applications of Product Subclass 7 in Organic Synthesis

6.1.7.7 Method 7: Formation of Diol Esters

6.1.7.7.1 Variation 1: Protection, Chromatographic Separations, and Analysis of Diols

6.1.7.7.2 Variation 2: Recognition of Sugar Molecules

6.1.7.8 Method 8: Use as Catalysts

6.1.7.8.1 Variation 1: For Hydroxyalkylation of Phenols

6.1.7.8.2 Variation 2: For Hydroalumination

6.1.7.8.3 Variation 3: For the Substitution of Epoxides

6.1.7.8.4 Variation 4: For Amidation of Carboxylic Acids

6.1.7.9 Method 9: C-C Bond Formation via the Boron-Mannich Reaction

6.1.7.10 Method 10: Metal-Catalyzed C-C and Carbon-Heteroatom Bond Formation

6.1.7.10.1 Variation 1: Palladium- and Nickel-Catalyzed Cross-Coupling Reactions

6.1.7.10.2 Variation 2: Rhodium-Catalyzed Addition Reactions

6.1.7.10.3 Variation 3: Copper-Catalyzed C-O, C-S, and C-N Bond Formation

6.1.8 Product Subclass 8: Boroxanes

M. Periasamy, M. Seenivasaperumal, and S. Sivakumar

6.1.8 Product Subclass 8: Boroxanes

Synthesis of Product Subclass 8

6.1.8.1 Method 1: Boroxin from Diborane

6.1.8.2 Method 2: Alkoxyboroxins from Boric Acids

6.1.8.3 Method 3: Alkylboroxin from the Corresponding Boronic Acid

6.1.8.3.1 Variation 1: An Alkylboroxin by Carbonylation of Borane–Dimethyl Sulfide Complex

6.1.8.3.2 Variation 2: Alkylboroxins from Organoboranes and Boric Oxide

6.1.8.4 Method 4: Arylboroxins from Arylboronic Acids

6.1.8.5 Method 5: A Diboroxane from Boric Acid

6.1.8.6 Method 6: Diboroxanes from Hydroxyboranes or Derivatives

6.1.8.7 Method 7: A Diboroxane from a Borepin

6.1.8.8 Method 8: 2,4,6-Trivinylboroxin–Pyridine from Trimethyl Borate

Applications of Product Subclass 8 in Organic Synthesis

6.1.8.9 Method 9: Oxidation of Alkoxyboroxins

6.1.8.10 Method 10: Boroxins in a Suzuki-Type Cross-Coupling Reaction

6.1.8.10.1 Variation 1: Preparation of 3,4-Disubstituted Furans

6.1.8.10.2 Variation 2: Preparation of Oligomeric Furans

6.1.8.10.3 Variation 3: Preparation of Substituted Styrenes

6.1.8.11 Method 11: Arylboroxins as Catalysts for Aldol or Michael Reactions

6.1.8.12 Method 12: Rhodium-Catalyzed Hydroarylation of Alkenes and Alkynes by Triarylboroxins

6.1.8.13 Method 13: Preparation of Chiral Oxazaborolidine Catalysts

6.1.8.14 Method 14: Separation of Diols

6.1.8.15 Method 15: Boroxin-Containing Polymers

6.1.8.16 Method 16: High Performance Polymer Electrolytes

6.1.8.17 Method 17: Resolution of 1,1'-Bi-2-naphthol

6.1.9 Product Subclass 9: Acyloxyboranes

M. Periasamy, M. N. Reddy, and N. S. Kumar

6.1.9 Product Subclass 9: Acyloxyboranes

Synthesis of Product Subclass 9

6.1.9.1 Method 1: Triacyloxyboranes and Oxybis(diacyloxy)boranes

6.1.9.2 Method 2: By the Reaction of 9-Borabicyclo[3.3.1]nonane with Carboxylic Acids

Applications of Product Subclass 9 in Organic Synthesis

6.1.9.3 Method 3: In Electrophilic Reactions

6.1.9.4 Method 4: Acyloxyborohydrides in Reduction Reactions

6.1.9.4.1 Variation 1: Reduction of Carboxylic Acids

6.1.9.4.2 Variation 2: Selective Reduction of the Carboxylic Acid Group in an Alkenic Acid

6.1.9.4.3 Variation 3: Hydroboration of Alkenes

6.1.9.4.4 Variation 4: Selective Hydroboration of Alkenic Acids

6.1.9.5 Method 5: Reduction of Carboxylic Acids to Aldehydes

6.1.9.6 Method 6: Asymmetric Reactions with Tartaric Acid Based Chiral Acyloxyboranes

6.1.9.6.1 Variation 1: Asymmetric Reduction

6.1.9.6.2 Variation 2: Diels-Alder Reactions

6.1.9.6.3 Variation 3: Aldol Reactions

6.1.9.6.4 Variation 4: Asymmetric Allylation

6.1.9.7 Method 7: Asymmetric Reactions with Amino Acid Based Chiral Acyloxyboranes

6.1.9.7.1 Variation 1: Diels-Alder Reactions

6.1.9.7.2 Variation 2: Aldol Reactions

6.1.10 Product Subclass 10: Vinyloxyboranes

C. Gennari, S. Ceccarelli, and U. Piarulli

6.1.10 Product Subclass 10: Vinyloxyboranes

Synthesis of Product Subclass 10

6.1.10.1 Method 1: From Carbonyl Compounds by Direct Enolization

6.1.10.1.1 Variation 1: Synthesis of Z(0)-Vinyloxyboranes

6.1.10.1.2 Variation 2: Synthesis of £(0)-Vinyloxyboranes

6.1.10.1.3 Variation 3: Synthesis of Vinyloxyboranes by Enolization of Aldehydes

6.1.10.2 Method 2: From Silyl Enol Ethers or Lithium Enolates

6.1.10.2.1 Variation 1: From Silyl Enol Ethers

6.1.10.2.2 Variation 2: From Lithium Enolates

6.1.10.3 Method 3: By Addition of Trialkyl- and Dialkylboranes to Double Bonds

6.1.10.3.1 Variation 1: By Addition to α,β-Unsaturated Carbonyl Compounds

6.1.10.3.2 Variation 2: By Addition to Ketenes

6.1.10.4 Method 4: Synthesis of Dialkyl Vinyl Borates by Oxidation of Dialkyl Vinylboronates

6.1.10.4.1 Variation 1: From Vinylic Grignard Reagents

6.1.10.4.2 Variation 2: By Hydroboration of Alkynes

6.1.10.5 Method 5: By Rearrangement of Boron “Ate” Complexes

6.1.10.5.1 Variation 1: From a-Halo-Substituted Enolates

6.1.10.5.2 Variation 2: From α-Diazo Carbonyl Compounds

6.1.10.5.3 Variation 3: From Stabilized Sulfur Ylides

6.1.10.6 Methods 6: Additional Methods

Applications of Product Subclass 10 in Organic Synthesis

6.1.10.7 Method 7: Synthesis of α-Halo Carbonyl Compounds by Halogenation of Vinyloxyboranes

6.1.10.8 Method 8: Synthesis of syn-α-Substituted β-Hydroxy Carbonyl Compounds by the Aldol Reaction

6.1.10.8.1 Variation 1: From Imide-Derived Vinyloxyboranes

6.1.10.8.2 Variation 2: From Sultam-Derived Vinyloxyboranes

6.1.10.8.3 Variation 3: From Ester-Derived Vinyloxyboranes

6.1.10.8.4 Variation 4: From Diisopinocampheyl(vinyloxy)boranes

6.1.10.8.5 Variation 5: From Vinyloxydiazaborolidines

6.1.10.8.6 Variation 6: From Dialkyl Vinyl Borates

6.1.10.8.7 Variation 7: From Monohalo- and Dihalo(vinyloxy)boranes

6.1.10.9 Method 9: Synthesis of anti-α-Substituted β-Hydroxy Carbonyl Compounds by the Aldol Reaction

6.1.10.9.1 Variation 1: From Imide-Derived Vinyloxyboranes with Excess Dibutyl{[(trifluoromethyl)sulfonyl]oxy}borane

6.1.10.9.2 Variation 2: From Sultam-Derived Vinyloxyboranes in the Presence of Lewis Acids

6.1.10.9.3 Variation 3: From Ester-Derived Vinyloxyboranes

6.1.10.9.4 Variation 4: From Vinyloxyboranes Bearing Menthone-Derived Chiral Ligands

6.1.10.9.5 Variation 5: From Vinyloxydiazaborolidines

6.1.10.9.6 Variation 6: Miscellaneous Reactions

6.1.10.10 Method 10: Synthesis of α-Unsubstituted β-Hydroxy Carbonyl Compounds by the Aldol Reaction

6.1.10.10.1 Variation 1: From 2,5-Dialkyl-1-(vinyloxy)borolanes

6.1.10.10.2 Variation 2: From Vinyloxyboranes Bearing Menthone-Derived Chiral Ligands

6.1.10.10.3 Variation 3: Miscellaneous Reactions

6.1.10.11 Method 11: Synthesis of β-Amino Carbonyl Compounds by Reaction with Imines

6.1.10.12 Method 12: Alkylation of Vinyloxyboranes (The Nicholas-Schreiber Reaction)

6.1.10.13 Method 13: Pericyclic Reactions

6.1.10.13.1 Variation 1: [3,3]-Sigmatropic Rearrangements

6.1.10.13.2 Variation 2: [2,3]-Sigmatropic Rearrangements

6.1.11 Product Subclass 11: Aryloxy- and Alkoxyboranes (Including Protecting Groups)

K. Ishihara and H.Yamamoto

6.1.11 Product Subclass 11: Aryloxy- and Alkoxyboranes (Including Protecting Groups)

Synthesis of Product Subclass 11

6.1.11.1 Method 1: Synthesis by Substitution

6.1.11.1.1 Variation 1: Of Boric Oxide or Hydroxyboranes with Alcohols

6.1.11.1.2 Variation 2: Of Borohydrides with Alcohols

6.1.11.1.3 Variation 3: Of Alkylboranes with Alcohols or Alkoxyboranes

6.1.11.1.4 Variation 4: Of Acyloxyboranes with Alcohols

6.1.11.1.5 Variation 5: Of Haloboranes with Alcohols

6.1.11.1.6 Variation 6: Of Thioboranes with Alcohols

6.1.11.1.7 Variation 7: Of Aminoboranes with Alcohols

6.1.11.2 Method 2: Synthesis by Addition Reactions

6.1.11.2.1 Variation 1: Oxidation of Alkylboranes with Peroxy Acids

6.1.11.2.2 Variation 2: Oxidation of Alkylboranes with Amine/V-Oxides

6.1.11.2.3 Variation 3: Oxidation of Alkylboranes with Molybdenum Peroxide-Pyridine-Hexamethylphosphoric Triamide

6.1.11.2.4 Variation 4: Oxidation of Alkylboranes with Molecular Oxygen

6.1.11.2.5 Variation 5: Reduction of Carbonyl Compounds with Hydroboranes

6.1.11.2.6 Variation 6: Alkylation of Carbonyl Compounds with Allenylboronic Esters

6.1.11.2.7 Variation 7: Alkylation of Carbonyl Compounds with Trialkylboranes

6.1.11.3 Method 3: Transesterification of Alkoxyboranes with Alcohols

Applications of Product Subclass 11 in Organic Synthesis

6.1.11.4 Method 4: Synthesis of Esters by Esterification of Carboxylic Acids with Alkoxyboranes

6.1.11.5 Method 5: The Protection of Hydroxy Groups

6.1.11.6 Method 6: Synthesis of Boronic Acids and Esters

6.1.11.6.1 Variation 1: Reduction

6.1.11.6.2 Variation 2: Electrophilic Reagent

6.1.11.6.3 Variation 3: Synthesis of α,β-Unsaturated Nitriles

6.1.11.6.4 Variation 4: Synthesis of Esters

6.1.11.6.5 Variation 5: Preparation of Potassium Triisopropylborohydride

6.1.11.7 Method 7: Use as a Lewis Acid Promoter or Catalyst

6.1.12 Product Subclass 12: Aryloxy- and Alkoxyborates

K. Ishihara and H. Yamamoto

6.1.12 Product Subclass 12: Aryloxy- and Alkoxyborates

Synthesis of Product Subclass 12

6.1.12.1 Method 1: By Reduction of Aldehydes or Ketones with Sodium Borohydride

6.1.12.2 Method 2: By Reaction of Alcohols with Sodium Borohydride

6.1.12.3 Method 3: Synthesis of Ammonium Tetraalkoxyborates and Related Compounds

Applications of Product Subclass 12 in Organic Synthesis

6.1.12.4 Method 4: Use as Brønsted Acid Assisted Chiral Lewis Acids

6.1.13 Product Subclass 13: Peroxyboranes

K. Ishihara and H. Yamamoto

6.1.13 Product Subclass 13: Peroxyboranes

Synthesis of Product Subclass 13

6.1.13.1 Method 1: Oxidation Reactions of Alkylboranes

6.1.13.1.1 Variation 1: Synthesis of Alkyl Hydroperoxides by Hydrolysis Following Oxidation

6.1.13.2 Method 2: Synthesis of Alcohols by the Redox Reaction of Alkyl(peroxy)boranes

6.1.14 Product Subclass 14: Sulfanyl- and Selanylboranes

C. Habben and D. E. Kaufmann

6.1.14 Product Subclass 14: Sulfanyl- and Selanylboranes

Synthesis of Product Subclass 14

6.1.14.1 Method 1: Sulfanylboranes by Substitution Reactions of Haloboranes with Organosulfur Compounds

6.1.14.1.1 Variation 1: From Haloboranes and Metal Thiolates

6.1.14.1.2 Variation 2: From Haloboranes and Thiols

6.1.14.2 Method 2: Additional Methods for the Synthesis of Sulfanylboranes

6.1.14.3 Method 3: Selanylboranes by Substitution Reactions of Haloboranes with Organoselenium Compounds

6.1.14.3.1 Variation 1: From Haloboranes and Selenides

6.1.14.3.2 Variation 2: From Haloboranes and Diselenides

6.1.14.4 Method 4: Additional Methods for the Synthesis of Selanylboranes

Applications of Product Subclass 14 in Organic Synthesis

6.1.14.5 Method 5: Metal–Sulfur Complexes

6.1.14.5.1 Variation 1: Complexes with Sulfanylboranes

6.1.14.5.2 Variation 2: Sulfur-Bridged Complexes

6.1.14.6 Method 6: Reactions with Loss of Boron

6.1.14.6.1 Variation 1: Addition Reactions of Sulfanylboranes

6.1.14.6.2 Variation 2: Substitution Reactions of Sulfanylboranes

6.1.14.6.3 Variation 3: Reactions of Selanylboranes

6.1.15 Product Subclass 15: Aminoboranes and Borane–Amine Complexes

B. Carboni and F. Carreaux

6.1.15 Product Subclass 15: Aminoboranes and Borane–Amine Complexes

Synthesis of Product Subclass 15

6.1.15.1 Method 1: Aminoboranes by Amination of Organoboranes

6.1.15.1.1 Variation 1: By Amines or Their Derivatives

6.1.15.1.2 Variation 2: By 1,2-Amino Alcohols

6.1.15.1.3 Variation 3: By Amino Acids

6.1.15.1.4 Variation 4: By 1,2-Diamines

6.1.15.2 Method 2: Aminoboranes by Redistribution and Exchange Reactions

6.1.15.3 Method 3: Aminoboranes by Borylation of Organometallic Reagents

6.1.15.4 Method 4: Aminoboranes by Reductive Alkylation of Azides

6.1.15.5 Method 5: Additional Methods for the Synthesis of Aminoboranes

6.1.15.6 Method 6: Borane–Amine Complexes by Complexation of Organoboranes

6.1.15.6.1 Variation 1: By Borane or Its Complexes

6.1.15.6.2 Variation 2: By Borohydrides

6.1.15.6.3 Variation 3: By Substituted Boranes or Their Derivatives

6.1.15.7 Method 7: Borane–Amine Complexes by Halogenation of Borane Complexes

6.1.15.7.1 Variation 1: By Halogens

6.1.15.7.2 Variation 2: By Hydrogen Halides

6.1.15.7.3 Variation 3: By Redistribution Reactions

6.1.15.7.4 Variation 4: By N-Halosuccinimides

6.1.15.8 Method 8: Additional Methods for the Synthesis of Borane–Amine Complexes

Applications of Product Subclass 15 in Organic Synthesis

6.1.15.9 Method 9: In Hydroboration Reactions

6.1.15.9.1 Variation 1: Hydroboration with Borane–Amine Complexes

6.1.15.9.2 Variation 2: Catalytic Asymmetric Hydroboration with Oxazaborolidines

6.1.15.10 Method 10: Reduction of Carbonyl and Imine Groups

6.1.15.10.1 Variation 1: Using Oxazaborolidine Catalysts

6.1.15.10.2 Variation 2: Using Borane–Amine Complexes

6.1.15.10.3 Variation 3: Using Aminoborohydrides

6.1.15.11 Method 11: α-Alkylation of Tertiary Amines

6.1.15.12 Method 12: Oxazaborolidinones as Protecting Groups

6.1.15.13 Method 13: Dioxazaborocines as Chiral Auxiliaries

6.1.15.14 Method 14: Aldol Reactions

6.1.15.14.1 Variation 1: With Stilbenediamine Derivatives (Stien Reagents) as Chiral Catalysts

6.1.15.14.2 Variation 2: With Oxazaborolidinone Catalysts

6.1.15.15 Method 15: Other Asymmetric Boron-Catalyzed Reactions

6.1.15.15.1 Variation 1: Diels–Alder Reactions

6.1.15.15.2 Variation 2: Enantioselective Addition to Carbonyl Compounds

6.1.15.15.3 Variation 3: 1,3-Dipolar Cycloaddition Reactions of Nitrones

6.1.15.16 Methods 16: Miscellaneous Applications

6.1.16 Product Subclass 16: Phosphinoboranes and Borane–Phosphine Complexes

A.C.Gaumont and B.Carboni

6.1.16 Product Subclass 16: Phosphinoboranes and Borane–Phosphine Complexes

Synthesis of Product Subclass 16

6.1.16.1 Method 1: Phosphinoboranes by Phosphination

6.1.16.1.1 Variation 1: From Halo(organo)boranes

6.1.16.1.2 Variation 2: From Amino(halo)boranes

6.1.16.2 Method 2: Phosphinoboranes by Elimination from Phosphine–Borane Complexes

6.1.16.2.1 Variation 1: By Dehydrohalogenation

6.1.16.2.2 Variation 2: By Thermal Dehydrogenation

6.1.16.2.3 Variation 3: By Elimination of Trimethylsilyl Groups

6.1.16.3 Method 3: By Catalytic Organometallic Dehydrocoupling

6.1.16.4 Method 4: Borane–Phosphine Complexes by Complexation of an Organoborane

6.1.16.4.1 Variation 1: From Phosphines and Uncomplexed Boranes

6.1.16.4.2 Variation 2: From Phosphines and Borane Complexes

6.1.16.4.3 Variation 3: From Chlorophosphines

6.1.16.4.4 Variation 4: From Borohydrides and Free Phosphines

6.1.16.4.5 Variation 5: From Phosphine Oxides

6.1.16.5 Method 5: Borane–Phosphine Complexes by Halogenation of Borane Complexes

6.1.16.6 Method 6: Additional Methods for the Synthesis of Borane–Phosphine Complexes

Applications of Product Subclass 16 in Organic Synthesis

6.1.16.7 Method 7: Borane as a Phosphorus Protecting Group

6.1.16.8 Method 8: Alkylation of Borane–Phosphine Complexes

6.1.16.8.1 Variation 1: C-Alkylation Reactions

6.1.16.8.2 Variation 2: P-Alkylation Reactions

6.1.16.8.3 Variation 3: Nucleophilic Substitution Reactions

6.1.16.9 Method 9: Hydrophosphination Reactions

6.1.16.10 Method 10: Coupling Reactions

6.1.16.10.1 Variation 1: Copper-Promoted Oxidative Coupling

6.1.16.10.2 Variation 2: Palladium-Promoted Cross Coupling

6.1.16.11 Methods 11: Miscellaneous Applications

6.1.17 Product Subclass 17: α-Metalloalkylboranes

Bakthan Singaram

6.1.17 Product Subclass 17: α-Metalloalkylboranes

Synthesis of Product Subclass 17

6.1.17.1 Method 1: Preparation of α-Borylboranes and α-Borylboronates

6.1.17.1.1 Variation 1: Hydroboration of Alkynes

6.1.17.1.2 Variation 2: Preparation of Bis-, Tris-, and Tetrakis(dimethoxyboryl)-methanes

6.1.17.2 Method 2: Metallation of Di-, Tri-, and Tetraborylmethanes by Deboronation

6.1.17.2.1 Variation 1: With Grignard Reagents

6.1.17.2.2 Variation 2: From gem-Tris- and Tetrakis(dialkoxyboryl) Compounds

6.1.17.3 Method 3: Deprotonation of α-Substituted Boranes and Boronates

6.1.17.3.1 Variation 1: Of Bis(dialkoxyboryl)methanes

6.1.17.3.2 Variation 2: Of α-(Phenylsulfanyl)methylboronates

6.1.17.3.3 Variation 3: Of α-(Trimethylsilyl)methylboronates

6.1.17.3.4 Variation 4: Of Dialkylvinylboranes

6.1.17.4 Method 4: Metal–Halogen Exchange Reactions of α-Haloalkylboranes and α-Haloalkylboronates

6.1.17.4.1 Variation 1: Preparation of α-(Trialkylstannyl)alkylboranes and α-(Trialkylstannyl)alkylboronates

6.1.17.4.2 Variation 2: Reaction of an α-Haloalkylboronate with tert-Butyllithium

6.1.17.4.3 Variation 3: Reaction of α-Haloalkylboronates with Zinc Metal and Subsequent Reaction with Copper(I) Cyanide

6.1.17.4.4 Variation 4: Reaction of α-Haloalkylboronates with Chromium(II) Chloride

6.1.17.5 Method 5: Deprotonation of Alkyl(dimesityl)boranes with Lithium Dialkylamides

6.1.17.6 Method 6: Deprotonation of Alkyl(dimesityl)boranes with Mesityllithium

6.1.17.7 Method 7: Generation of α-Metalloalkylboranes by Organometallic Addition to Alkenylboranes

6.1.17.8 Method 8: Generation of α-Metalloalkenylboranes

Applications of Product Subclass 17 in Organic Synthesis

6.1.17.9 Method 9: Alkylation of α-Metalloalkylboranes

6.1.17.10 Method 10: Synthesis of Alkenes

6.1.17.10.1 Variation 1: Synthesis of Allenes

6.1.17.10.2 Variation 2: Synthesis of Vinylboronates

6.1.17.11 Method 11: Preparation of Carbonyl Compounds

6.1.17.12 Method 12: Preparation of 1,2-Diols

6.1.17.13 Method 13: Preparation of 1,3-Diols

6.1.17.14 Method 14: Synthesis of Alcohols

6.1.17.15 Method 15: Preparation of Amino Alcohols

6.1.18 Product Subclass 18: Cyanoboranes

D.Gabel and M.B.El-Zaria

6.1.18 Product Subclass 18: Cyanoboranes

Synthesis of Product Subclass 18

6.1.18.1 Method 1: Cyanoborane–Amine Complexes by Substitution of Hydrogen in Borane–Amine Complexes

6.1.18.2 Method 2: Dicyanoborane–Amine Complexes by Substitution of Hydrogen in Cyanoborane

6.1.18.3 Method 3: From Borohydrides and Mercury(II) Cyanide

6.1.18.4 Method 4: Cyanoboranes by Substitution of the Carboxamide Group in Carbamoylboranes

6.1.18.5 Method 5: Cyanoboranes by Substitution of Halides in Haloboranes

6.1.18.5.1 Variation 1: By Cyanogen Iodide

6.1.18.5.2 Variation 2: By Trimethylsilyl Cyanide

6.1.18.5.3 Variation 3: By Cyanide

6.1.18.5.4 Variation 4: By Isocyanoboranes

6.1.18.6 Method 6: Trialkylcyanoborates by Complexation of Trialkylboranes with Cyanide

6.1.18.7 Method 7: Chelation of Potassium Cyanide by Boronates Containing Crown Ether Ligands

6.1.18.8 Method 8: Monomeric Cyanoborane–Amine Complexes from Amines and Oligomeric Cyanoborane

6.1.18.9 Method 9: Cyanoborane Complexes from Sodium Cyanoborohydride

6.1.18.9.1 Variation 1: By Reaction with Amine Hydrochlorides To Give Cyanoborane–Amine Complexes

6.1.18.9.2 Variation 2: By Reaction with Phosphines To Give Cyanoborane–Phosphine Complexes

6.1.18.9.3 Variation 3: By Reaction with Halogens To Give Oligomeric Cyanoborane

6.1.18.10 Method 10: B-Alkylation of Cyanoboranes

6.1.18.11 Method 11: Exchange of the Donor Ligands of Cyanoborane–Amine, –Phosphine, –Phosphite, and –Dimethyl Sulfide Complexes

Applications of Product Subclass 18 in Organic Synthesis

6.1.18.12 Method 12: Ethylation of Cyanoboranes To Give N-Ethylnitriliumborane Salts

6.1.18.13 Method 13: Preparation of Ketones

6.1.18.14 Method 14: Formation of Clathrates

6.1.18.15 Method 15: Reduction of Ketones

6.1.18.16 Method 16: Preparation of Alkyl Cyanides

6.1.19 Product Subclass 19: Carboxyboranes and Related Derivatives

D.Gabel and M.B.El-Zaria

6.1.19 Product Subclass 19: Carboxyboranes and Related Derivatives

Synthesis of Product Subclass 19

6.1.19.1 Method 1: From Cyanoboranes

6.1.19.1.1 Variation 1: Carboxy-, Carbamoyl-, and (Alkoxycarbonyl)boranes from Cyanoboranes

6.1.19.1.2 Variation 2: [(Alkylimino)(alkoxy)methyl]boranes from Cyanoboranes

6.1.19.1.3 Variation 3: Sulfur and Nitrogen Analogues of Carboxy- and Carbamoylboranes from Cyanoboranes

6.1.19.2 Method 2: Carbamoylboranes from Carboxyboranes

6.1.19.3 Method 3: (Alkoxycarbonyl)boranes from Carboxyboranes

6.1.19.3.1 Variation 1: Acid-Catalyzed Esterification of Carboxyboranes

6.1.19.3.2 Variation 2: Esterification of Carboxyboranes in the Presence of Activating Agents

6.1.19.3.3 Variation 3: Esterification of Carboxyboranes under Basic Conditions

6.1.19.4 Method 4: (Alkoxycarbonyl)boranes from Carbamoylboranes

6.1.19.5 Method 5: Carbamoylborane from the Carbonyl–Borane Adduct

6.1.19.6 Method 6: Carboxy- and Carbamoylboranes from Haloboranes

6.1.19.7 Method 7: Exchange of the Donor Ligands of Borane Adducts

6.1.19.8 Method 8: Ligand-Exchange Reactions of (Methoxycarbonyl)borane–Amines

Applications of Product Subclass 19 in Organic Synthesis

6.1.19.9 Method 9: Alkylboranes by Reduction of Carboxyboranes

6.1.19.10 Method 10: Haloboranes from Carboxyboranes

6.1.20 Product Subclass 20: α-Haloalkylboronates

D.S.Matteson

6.1.20 Product Subclass 20: α-Haloalkylboronates

Synthesis of Product Subclass 20

6.1.20.1 Method 1: Synthesis via (Dihalomethyl)borate Anions

6.1.20.1.1 Variation 1: Boronates with Preformed (Dichloromethyl)lithium

6.1.20.1.2 Variation 2: From (Dihalomethyl)lithiums Generated In Situ

6.1.20.1.3 Variation 3: From (Dihalomethyl)boronates and Organometallic Reagents

6.1.20.1.4 Variation 4: From Achiral Boronates with an Asymmetric Catalyst

6.1.20.2 Method 2: From Haloalkyllithiums and Trialkyl Borates

6.1.20.3 Method 3: α-Substitution Routes

6.1.20.3.1 Variation 1: Halogenation of Alkylboronates

6.1.20.3.2 Variation 2: From α-Metalloalkylboronates

6.1.20.3.3 Variation 3: Via Nucleophilic Displacements

6.1.20.4 Method 4: Addition of Halogen Compounds to Alkenylboranes

6.1.20.4.1 Variation 1: Addition of Hydrogen Halides

6.1.20.4.2 Variation 2: Radical Additions of Halocarbons

6.1.20.4.3 Variation 3: Halogenations

6.1.20.5 Methods 5: Additional Methods

6.1.21 Product Subclass 21: α-Alkoxyalkyl-, α-Sulfanylalkyl-, and α-Aminoalkylboronates

D.S.Matteson

6.1.21 Product Subclass 21: α-Alkoxyalkyl-, α-Sulfanylalkyl-, and α-Aminoalkylboronates

Synthesis of Product Subclass 21

6.1.21.1 Method 1: Synthesis from α-Haloalkylboronates

6.1.21.1.1 Variation 1: Alkoxide Substitutions

6.1.21.1.2 Variation 2: Synthesis of α-Aminoalkyl- and α-Amidoalkylboronates

6.1.21.1.3 Variation 3: Azide Substitution

6.1.21.1.4 Variation 4: Thiolate Substitution

6.1.21.2 Method 2: Synthesis from α-Lithio Ethers and Sulfides

6.1.21.2.1 Variation 1: From (Diethoxymethyl)lithium and Boronates

6.1.21.2.2 Variation 2: From [(Phenylsulfanyl)methyl]lithium and Trimethyl Borate

6.1.21.2.3 Variation 3: Alkylation of Lithiated [α-(Phenylsulfanyl)alkyl]boronates

6.1.21.3 Methods 3: Additional Methods

6.1.22 Product Subclass 22: α-Phosphinoalkylboranes

D.S.Matteson

6.1.22 Product Subclass 22: α-Phosphinoalkylboranes

Synthesis of Product Subclass 22

6.1.22.1 Method 1: Addition of Boranes to Alkylidenephosphoranes

6.1.22.1.1 Variation 1: Addition of Hydroboranes

6.1.22.1.2 Variation 2: Addition of Haloboranes

6.1.22.1.3 Variation 3: Addition of Triorganoboranes

6.1.22.2 Method 2: Reaction of α-Haloalkylboranes with Phosphines

6.1.22.3 Methods 3: Other Methods

6.1.23 Product Subclass 23: Alk-1-ynylboranes and Alkyn-1-ylboronates

D.E.Kaufmann and N.Öcal

6.1.23 Product Subclass 23: Alk-1-ynylboranes and Alkyn-1-ylboronates

Synthesis of Product Subclass 23

6.1.23.1 Method 1: From Alk-1-ynylborane-Amine Adducts

6.1.23.2 Method 2: By Metal-Boron Exchange Reactions

6.1.23.2.1 Variation 1: From Alk-1-ynyllithium and Alkoxy(dialkyl)boranes or Diorganohaloboranes

6.1.23.2.2 Variation 2: From Alk-1-ynyllithium, Alk-1-ynylsodium, or Alk-1-ynyl-magnesium Compounds and Dialkyl (Organo)boronates, Trialkyl Borates, Dialkoxyhaloboranes, and Dialkylamino- or Bis(dialkylamino)haloboranes

6.1.23.2.3 Variation 3: From Alk-1-ynyltin Compounds and Boron Halides

6.1.23.3 Methods 3: Additional Methods

Applications of Product Subclass 23 in Organic Synthesis

6.1.23.4 Method 4: Substitution of the Boryl Group

6.1.23.4.1 Variation 1: Synthesis of Propargylic Alcohols

6.1.23.4.2 Variation 2: Synthesis of Propargylic Amines, Allenes, and α-Alkynylazacycloalkanes

6.1.23.4.3 Variation 3: Synthesis of Homopropargylic Alcohols

6.1.23.4.4 Variation 4: Synthesis of α- and γ-Alkynyl Ketones

6.1.23.4.5 Variation 5: Synthesis of Alkynoylureas

6.1.23.5 Method 5: Addition Reactions to the Alkynyl Group

6.1.23.5.1 Variation 1: Hydrogenation and Hydrozirconation

6.1.23.5.2 Variation 2: Hydrostannation, Hydrophosphination, and Hydrothiolation

6.1.23.5.3 Variation 3: Cycloalkylation Reactions

6.1.23.6 Method 6: Cycloaddition Reactions

6.1.23.6.1 Variation 1: Diels-Alder Reactions

6.1.23.6.2 Variation 2: Catalyzed Cyclotrimerization Reactions

6.1.24 Product Subclass 24: Borylketenes

D.Gabel

6.1.24 Product Subclass 24: Borylketenes

Synthesis of Product Subclass 24

6.1.24.1 Method 1: Boryl(silyl)ketenes from Ethoxyacetylenes, Halosilanes, and Bromoboranes

6.1.24.1.1 Variation 1: From Ethoxy(silyl)acetylenes and Bromoboranes

6.1.24.1.2 Variation 2: From Boryl(ethoxy)acetylenes and Halosilanes

6.1.24.2 Method 2: Modification of Boryl(silyl)ketenes by Replacement of the Substituents on Boron

Applications of Product Subclass 24 in Organic Synthesis

6.1.24.3 Method 3: Preparation of Substituted Carbonyl Compounds

6.1.25 Product Subclass 25: Allenylboranes

D.E.Kaufmann and C.Burmester

6.1.25 Product Subclass 25: Allenylboranes

Synthesis of Product Subclass 25

6.1.25.1 Method 1: Borylation of Organometallic Compounds

6.1.25.2 Method 2: From Propargyl Chlorides or Acetates and Trialkylboranes

6.1.25.3 Method 3: Hydroboration of Enynes

Applications of Product Subclass 25 in Organic Synthesis

6.1.25.4 Method 4: Reaction with Carbonyl Compounds

6.1.25.5 Method 5: Reaction with Protic Acids

6.1.25.5.1 Variation 1: Reaction with Water

6.1.25.5.2 Variation 2: Deborylation by Acetic Acid

6.1.26 Product Subclass 26: Aryl- and Hetarylboranes

N.Miyaura

6.1.26 Product Subclass 26: Aryl- and Hetarylboranes

Synthesis of Product Subclass 26

6.1.26.1 Method 1: Transmetalation Reactions

6.1.26.1.1 Variation 1: Via Magnesium and Lithium Reagents

6.1.26.1.2 Variation 2: Via Tin Reagents

6.1.26.2 Methods 2: Additional Methods

Applications of Product Subclass 26 in Organic Synthesis

6.1.26.3 Method 3: As Catalysts

6.1.26.3.1 Variation 1: For Aldol Reactions

6.1.26.3.2 Variation 2: For Diels–Alder Reactions

6.1.26.3.3 Variation 3: For the Rearrangement of Epoxides

6.1.26.3.4 Variation 4: For the Reduction of Carbonyl Compounds

6.1.26.3.5 Variation 5: For Hydrostannation

6.1.26.4 Method 4: Arylation of Organic Electrophiles

6.1.26.5 Method 5: Copper-Mediated C—C Bond Formation

6.1.27 Product Subclass 27: Dienylboranes

K.Albrecht and D.E.Kaufmann

6.1.27 Product Subclass 27: Dienylboranes

Synthesis of Product Subclass 27

6.1.27.1 Method 1: Metal-Boron Exchange Reactions

6.1.27.1.1 Variation 1: Borylation of Dienyllithium and Dienylsodium Compounds

6.1.27.1.2 Variation 2: From Dienyl- and Trienylstannanes and Zirconium Metallacycles

6.1.27.2 Method 2: Palladium-Catalyzed Coupling of Vinylboronates

6.1.27.2.1 Variation 1: Heck and Suzuki-Miyaura Reactions

6.1.27.2.2 Variation 2: Cross Coupling of Vinylzinc Compounds with (2-Halovinyl)boronates

6.1.27.3 Method 3: Zirconium-Mediated Dimerization of Alkynylboronates

6.1.27.4 Method 4: By Elimination Reactions of Functionalized Organoboronates

6.1.27.5 Method 5: Addition Reactions to Enynes and Diynes

6.1.27.5.1 Variation 1: Addition of Hydroboranes and Hydroboronates

6.1.27.5.2 Variation 2: Addition of Haloboranes

6.1.27.5.3 Variation 3: Addition of Organoboranes

6.1.27.6 Method 6: Migration of Alkenyl Groups from Boron to Carbon

6.1.27.6.1 Variation 1: Migration of Alkyl Groups from Boron to Carbon

6.1.27.7 Methods 7: Additional Methods

Applications of Product Subclass 27 in Organic Synthesis

6.1.27.8 Method 8: Formation of Cyclohexenylboronates via the Diels-Alder Reaction

6.1.27.9 Method 9: Oxidation to α,β-Unsaturated Ketones

6.1.27.10 Method 10: 1,4-Addition of Dienylboronates and Dienylboronic Acids to Unsaturated Carbonyl Compounds

6.1.27.11 Method 11: Synthesis of Substituted Homoallylic Alcohols via 2,5-Dihydro-1 H-boroles

6.1.27.12 Method 12: Formation of Butatrienes by Elimination

6.1.27.13 Method 13: Substitution of the Boron Group

6.1.27.13.1 Variation 1: Synthesis of Substituted Dienes

6.1.27.13.2 Variation 2: Stereoselective Synthesis of Iodinated Dienes

6.1.27.13.3 Variation 3: Palladium-Catalyzed Synthesis of Polyene Carbon Frameworks (Suzuki-Miyaura Reaction)

6.1.28 Product Subclass 28: Vinylboranes

M.Vaultier and G.Alcaraz

6.1.28 Product Subclass 28: Vinylboranes

Synthesis of Product Subclass 28

6.1.28.1 Method 1: Dehydrogenative Boration of Alkenes

6.1.28.2 Method 2: By Metal–Boron Exchange

6.1.28.2.1 Variation 1: From Vinylsilanes

6.1.28.2.2 Variation 2: From Vinylstannanes

6.1.28.2.3 Variation 3: From Vinylated Transition Metals

6.1.28.3 Method 3: By Elimination Reactions

6.1.28.4 Method 4: Boron-Wittig Reaction of Di- or Tri(boryl)methides and Aldehydes

6.1.28.5 Method 5: By the Peterson Alkenation

6.1.28.6 Method 6: From Aldehydes and 1,1-Dimetalated Methylboronic Esters

6.1.28.7 Method 7: Hydroboration of Alkynes and Allenes

6.1.28.7.1 Variation 1: With Borane

6.1.28.7.2 Variation 2: With Monosubstituted Boranes

6.1.28.7.3 Variation 3: With Disubstituted Boranes

6.1.28.7.4 Variation 4: Catalyzed Hydroboration

6.1.28.8 Method 8: Hydrozirconation of Alkynylboranes

6.1.28.9 Method 9: Hydrogenation of Alkyn-1-ylboranes

6.1.28.10 Method 10: 1,1-Organoboration of Alkynes

6.1.28.11 Method 11: Allylboration of Alkynes

6.1.28.12 Method 12: Carbometalation of Alkynylboranes

6.1.28.13 Method 13: Haloboration of Alkynes

6.1.28.14 Method 14: Boracyclopropenation of Alkynes

6.1.28.15 Method 15: Catalyzed Dimetalation

6.1.28.15.1 Variation 1: Diboration of Alkynes, Allenes, and Methylidenecyclopropanes

6.1.28.15.2 Variation 2: Sulfanylboration of Alkynes

6.1.28.15.3 Variation 3: Silaboration of Alkynes, Allenes, and Alkylidenecyclopropanes

6.1.28.15.4 Variation 4: Stannaboration and Germaboration of Alkynes and Allenes

6.1.28.15.5 Variation 5: Boraruthenation of Alkynes

6.1.28.16 Method 16: By Rearrangement of Trialkyl(alkynyl)borates

6.1.28.17 Method 17: By Diels–Alder Reactions of Dienylboronates and Alkynylboranes

6.1.28.17.1 Variation 1: From Alkynylboranes and Dienes

6.1.28.17.2 Variation 2: From Dienylboronates and Dienophiles

6.1.28.18 Method 18: Radical Additions to Alkynylboranes

6.1.28.19 Method 19: Photolytic Rearrangement of Alkynylboranes

6.1.28.20 Method 20: By the Isomerization of Allylboranes

Applications of Product Subclass 28 in Organic Synthesis

6.1.28.21 Method 21: Formation of a Metal-Carbon Bond

6.1.28.22 Method 22: Formation of a Heteroatom-Carbon Bond

6.1.28.22.1 Variation 1: Halogen-Carbon Bonds

6.1.28.22.2 Variation 2: Chalcogen-Carbon Bonds

6.1.28.22.3 Variation 3: Nitrogen-Carbon and Oxygen-Carbon Bonds

6.1.28.22.4 Variation 4: Group 14 Metal-Carbon Bonds

6.1.28.23 Method 23: Formation of a C-C Bond

6.1.28.23.1 Variation 1: With α-Boron Substitution

6.1.28.23.2 Variation 2: Carbometalation Reactions

6.1.28.23.3 Variation 3: Radical Addition Reactions

6.1.28.23.4 Variation 4: Cyclopropanation Reactions

6.1.28.23.5 Variation 5: By Alkene Cross-Metathesis

6.1.28.23.6 Variation 6: Homologation Reactions

6.1.28.23.7 Variation 7: By Isomerization

6.1.28.23.8 Variation 8: Pericyclic Reactions

6.1.28.23.9 Variation 9: Cross-Coupling Reactions

6.1.28.23.10 Variation 10: 1,4-Addition Reactions

6.1.28.23.11 Variation 11: Multicomponent Reactions

6.1.28.23.12 Variation 12: Boron-Stabilized Alkenyl Carbanions

6.1.29 Product Subclass 29: α-Boryl Carbonyl Compounds

H.Abu Ali, V.M.Dembitsky, and M.Srebnik

6.1.29 Product Subclass 29: α-Boryl Carbonyl Compounds

Synthesis of Product Subclass 29

6.1.29.1 Method 1: Synthesis of 5-Ethyl-2,3-dimethyl-2,3-dihydro-1,2,3-diaza-borine-4-carbaldehyde by Halogen Replacement

6.1.29.2 Method 2: Synthesis of 5-(Dihydroxyboryl)uracil by Halogen–Metal Exchange

6.1.29.3 Method 3: Formation of α,N-Borylamides by Substitution

6.1.29.4 Method 4: Metal-Exchange Reactions of Diazo Compounds

6.1.29.5 Method 5: Reaction of Bis(methoxycarbonylmethyl)mercury with Alkylbromo(dimethylamino)boranes

6.1.29.6 Method 6: Hydroboration of Functionalized Alkenes

6.1.29.7 Method 7: Hydroboration of Methyl 2-(Acetylamino)acrylate

6.1.29.8 Method 8: Hydroboration of Unsaturated Esters

6.1.29.9 Method 9: Hydroboration of Enehydrazones

6.1.29.10 Method 10: Aminoboration of Ketene

6.1.29.11 Method 11: Haloboration of Triple Bonds

6.1.29.12 Method 12: Ozonolysis of (Trifluoromethyl)(trifluorovinyl)boron Derivatives

6.1.29.13 Method 13: Synthesis of Quinone Boronates

Applications of Product Subclass 29 in Organic Synthesis

6.1.29.14 Method 14: Synthesis of Novel Alkaloids

6.1.29.15 Method 15: α-Alkyl Ketones by the Reaction of Trialkylboranes with α-Bromo Ketones

6.1.30 Product Subclass 30: β-Haloalkylboranes

H.Abu Ali, V.M.Dembitsky, and M.Srebnik

6.1.30 Product Subclass 30: β-Haloalkylboranes

Synthesis of Product Subclass 30

6.1.30.1 Method 1: Hydroboration of Haloalkenes

6.1.30.1.1 Variation 1: (β-Fluoroalkyl)boranes from (Perfluoroalkyl)ethenes

6.1.30.1.2 Variation 2: Hydroboration of Vinylic Halides

6.1.30.1.3 Variation 3: Hydroboration of Allylic Chlorides

6.1.30.1.4 Variation 4: Hydroboration of Chloroalkynes

6.1.30.2 Method 2: Addition of Hydrogen Halides to Vinylboronates

6.1.30.3 Method 3: Haloboration of Unsaturated Compounds

6.1.30.3.1 Variation 1: Haloboration of Alkenes

6.1.30.3.2 Variation 2: Haloboration of Alkynes

6.1.30.4 Method 4: Cycloaddition to Alkenylboranes

6.1.30.4.1 Variation 1: Cyclopropanation of a Vinylboronate

6.1.30.4.2 Variation 2: Diels-Alder Reaction of Alkenylboranes and Alkenylboronates

Applications of Product Subclass 30 in Organic Synthesis

6.1.30.5 Method 5: Halogenation of Unsaturated Boranes

6.1.30.5.1 Variation 1: Addition of Halogens to Alkenylboranes and Alkenylboronates

6.1.30.5.2 Variation 2: Zweifel’s Stereocontrolled Alkene Synthesis

6.1.30.5.3 Variation 3: Zweifel’s Stereocontrolled Diene Synthesis

6.1.31 Product Subclass 31: β-Alkoxyalkyl-, β-Sulfanylalkyl-, and β-Aminoalkylboranes

H.Abu Ali, V.M.Dembitsky, and M.Srebnik

6.1.31 Product Subclass 31: β-Alkoxyalkyl-, β-Sulfanylalkyl-, and β-Aminoalkylboranes

Synthesis of Product Subclass 31

6.1.31.1 β-Alkoxyalkylboranes

6.1.31.1.1 Method 1: Hydroboration of Enol Ethers

6.1.31.1.2 Method 2: Hydroboration of Allylic Ethers

6.1.31.1.3 Method 3: Catalytic Borylation

6.1.31.1.4 Method 4: Carbon Chain Extension

6.1.31.2 β-Sulfanylalkylboranes

6.1.31.2.1 Method 1: Hydroboration of Alkenyl Sulfides

6.1.31.2.2 Method 2: Addition of Thiols to Alkenylboranes

6.1.31.2.3 Method 3: Thioboration of Ethoxyacetylene

6.1.31.3 β-Aminoalkylboranes

6.1.31.3.1 Method 1: Hydroboration of Enamines and Allylic Amines

6.1.31.3.2 Method 2: Carbon Chain Extension

6.1.32 Product Subclass 32: β-Silylalkyl- and β-Stannylalkylboranes

P.J.Murphy

6.1.32 Product Subclass 32: β-Silylalkyl- and β-Stannylalkylboranes

Synthesis of Product Subclass 32

6.1.32.1 Method 1: From Methoxyborinanes and Methoxyborolanes

6.1.32.2 Method 2: Hydroboration of Alkynes

6.1.32.3 Method 3: Hydroboration of Vinylsilanes

6.1.32.3.1 Variation 1: Using Borane Complexes

6.1.32.3.2 Variation 2: Using Borane-Dimethyl Sulfide Complex

6.1.32.3.3 Variation 3: Using Triisobutylborane

6.1.32.3.4 Variation 4: Using Hindered Boranes

6.1.32.3.5 Variation 5: Using Bis(pentafluorophenyl)borane

6.1.32.3.6 Variation 6: Of Divinylsilanes

6.1.32.3.7 Variation 7: Using (-)-Diisopinocampheylborane

6.1.32.4 Method 4: Heterocycles by Hydroboration

6.1.32.4.1 Variation 1: Using tert-Butylborane-Trimethylamine Complex

6.1.32.4.2 Variation 2: Using Borane-Dimethyl Sulfide Complex

6.1.32.4.3 Variation 3: Using 1,1-Dimethyl-1,4-silaborinane

6.1.32.5 Method 5: Silylation of Vinylboranes

6.1.32.6 Method 6: From a Diborirane

6.1.32.7 Method 7: From Tetrahalodiboranes(4) and Vinylsilanes

6.1.32.8 Method 8: From Tetrachlorodiborane(4) and Vinylstannanes

6.1.32.9 Method 9: Addition to Z-2-Boryl-1-stannylalkenes with Rearrangement

6.1.32.10 Method 10: Alkyl and Aryl Migration

Applications of Product Subclass 32 in Organic Synthesis

6.1.32.11 Method 11: Synthesis of Methoxyborinanes

6.1.32.12 Method 12: Synthesis of Methoxyboranes and Methylboronates via Butylsulfanylboranes

6.1.32.13 Method 13: Synthesis of Methoxyboranes by Boron Exchange

6.1.33 Product Subclass 33: Propargylboranes

D.E.Kaufmann and C.Burmester

6.1.33 Product Subclass 33: Propargylboranes

Synthesis of Product Subclass 33

6.1.33.1 Method 1: By Transmetalation Reactions

6.1.33.1.1 Variation 1: Borylation of Lithium or Magnesium Compounds

6.1.33.1.2 Variation 2: Borylation of Stannanes

6.1.33.2 Method 2: By Rearrangement of “Ate” Complexes

6.1.33.2.1 Variation 1: By One-Carbon Homologation of Boronates

6.1.33.2.2 Variation 2: From α-Haloalkylboronates

Applications of Product Subclass 33 in Organic Synthesis

6.1.33.3 Method 3: Reaction with Carbonyl Compounds

6.1.33.4 Method 4: Oxidation

6.1.34 Product Subclass 34: Benzylboranes and Benzylboronates

M.Zaidlewicz and J.Meller

6.1.34 Product Subclass 34: Benzylboranes and Benzylboronates

Synthesis of Product Subclass 34

6.1.34.1 Method 1: Transmetalation

6.1.34.1.1 Variation 1: From Haloboranes and Benzylic Organometallics

6.1.34.1.2 Variation 2: From Alkoxyboranes or Alkylboronates and Benzylic Organometallics

6.1.34.1.3 Variation 3: From Trialkyl- or Triarylboranes and Benzylic Organometallics

6.1.34.2 Method 2: Redistribution

6.1.34.3 Method 3: Hydroboration

6.1.34.3.1 Variation 1: Hydroboration with Boranes and Hydroborates

6.1.34.3.2 Variation 2: Catalytic Hydroboration

6.1.34.4 Method 4: Homologation

6.1.34.5 Method 5: From Benzyl Halides by a Cross-Coupling Reaction

6.1.34.6 Method 6: Benzylic C-H Borylation

6.1.34.7 Method 7: From Borane and Ylides

6.1.34.8 Method 8: From Benzylic Hydroborates

Applications of Product Subclass 34 in Organic Synthesis

6.1.34.9 Method 9: Protonolysis

6.1.34.10 Method 10: Oxidation

6.1.34.11 Method 11: Amination

6.1.34.12 Method 12: Haloboration

6.1.34.13 Method 13: Carbaboration

6.1.34.14 Method 14: Dichloromethyl Methyl Ether Reaction

6.1.34.15 Method 15: Cross-Coupling Reaction

6.1.34.16 Method 16: Formation of Benzylborates

6.1.34.16.1 Variation 1: Benzylborohydrides

6.1.34.16.2 Variation 2: Alkylarylbenzylborates and Benzylcyanoborates

6.1.34.17 Method 17: Transmetalation

6.1.35 Product Subclass 35: Allylboranes

Y.Bubnov

6.1.35 Product Subclass 35: Allylboranes

Synthesis of Product Subclass 35

6.1.35.1 Method 1: Transmetalation

6.1.35.1.1 Variation 1: From Allylic Tin Compounds and Boron Halides

6.1.35.1.2 Variation 2: Via Aluminum Sesquibromides

6.1.35.1.3 Variation 3: From Allylmagnesium Halides

6.1.35.1.4 Variation 4: From Alkenes via Lithium and Potassium Derivatives

6.1.35.1.5 Variation 5: Via Lithiation of Penta-1,3- and Penta-1,4-dienes, Polyenes, and Aromatic Compounds

6.1.35.1.6 Variation 6: Via Lithiated Allylic Halides, Ethers, Sulfides, and Selenides

6.1.35.1.7 Variation 7: From Allylsilanes

6.1.35.2 Method 2: By Hydroboration

6.1.35.2.1 Variation 1: Via Hydroboration of Propargyl Compounds

6.1.35.2.2 Variation 2: Hydroboration of Allenes

6.1.35.2.3 Variation 3: Hydroboration of 1,3-Dienes

6.1.35.2.4 Variation 4: Hydroboration–Cyclization of 1-En-3-ynes

6.1.35.3 Method 3: Haloboration of Allenes

6.1.35.4 Method 4: Diboration, Silaboration, and Stannaboration of 1,3-Dienes and Allenes

6.1.35.4.1 Variation 1: Diboration of 1,3-Dienes and Allenes

6.1.35.4.2 Variation 2: 1,4-Silaboration of 1,3-Dienes

6.1.35.4.3 Variation 3: 1,4-Stannaboration of 1,3-Dienes and Allenes

6.1.35.5 Method 5: From 1,3-Dienylboranes via Diels–Alder Reaction

6.1.35.6 Method 6: Cross-Coupling Reactions of Diborane Derivatives with Allylic Acetates

6.1.35.7 Method 7: From Trialkyl(alkynyl)borates via a 1,2-Anionotropic Rearrangement

6.1.35.8 Method 8: From Trialkylboranes and Alkynyl Derivatives of Tin and Silicon

6.1.35.9 Method 9: Homologation of Vinylic Boranes

6.1.35.10 Method 10: Vinylation of Haloalkylboron Derivatives

6.1.35.11 Method 11: From Triallylboranes

6.1.35.11.1 Variation 1: Redistribution Reactions with Boric and Thioboric Esters

6.1.35.11.2 Variation 2: Reactions with Protolytic Reagents

6.1.35.11.3 Variation 3: Reactions with Carbonyl Compounds, Acids, and Esters

6.1.35.11.4 Variation 4: Reactions with Nitriles and Imines

6.1.35.11.5 Variation 5: Reaction with Cyclopropenes

6.1.35.12 Method 12: From Triallylic Organoboranes and Alkynes or Allenes

6.1.35.12.1 Variation 1: Diallyl(penta-1,4-dienyl)boranes

6.1.35.12.2 Variation 2: 1-Allylborin Derivatives

6.1.35.12.3 Variation 3: 3-Allyl-3-borabicyclo[3.3.1]non-6-enes

6.1.35.12.4 Variation 4: Reactions of Allylic Boranes with Allenes

6.1.35.13 Method 13: From Aminoboranes via [2+4]-Cycloaddition and Ene Reactions

6.1.35.14 Method 14: Via Ring Closure and Cross-Metathesis

6.1.35.15 Methods 15: Miscellaneous Methods

Applications of Product Subclass 35 in Organic Synthesis

6.1.35.16 Method 16: Complexation

6.1.35.17 Method 17: Allylboration of Organic Compounds Containing a Multiple Bond

6.1.35.18 Method 18: Reductive Mono- and trans-α,α'-Diallylation of Aromatic Nitrogen Heterocycles with Allylic Boranes

6.1.35.19 Methods 19: Miscellaneous Applications

6.1.36 Product Subclass 36: β-Boryl Carbonyl Compounds

D.S.Matteson

6.1.36 Product Subclass 36: β-Boryl Carbonyl Compounds

Synthesis of Product Subclass 36

6.1.36.1 Method 1: From a-Haloalkylboronates

6.1.36.1.1 Variation 1: From Ester Enolates

6.1.36.1.2 Variation 2: From Oxazolidinone Enolates

6.1.36.1.3 Variation 3: From α-Cyano Carbanions

6.1.36.2 Method 2: Oxidation of γ-Hydroxy Boronates

6.1.36.3 Methods 3: Additional Methods

6.1.37 Product Subclass 37: γ-Haloalkylboranes

H.Abu Ali, V.M.Dembitsky, and M.Srebnik

6.1.37 Product Subclass 37: γ-Haloalkylboranes

Synthesis of Product Subclass 37

6.1.37.1 Method 1: Formation of B-(γ-Fluoroalkyl)borazine Derivatives by Substitution

6.1.37.2 Method 2: Hydroboration of Allylic Halides

6.1.37.3 Method 3: Synthesis of 1-Boraadamantane Derivatives via Hydroboration

6.1.37.4 Method 4: Synthesis of Chloronorbornane Derivatives by Hydroboration or Chloroboration

6.1.37.5 Method 5: Diboration of Haloalkenes

6.1.37.6 Method 6: Synthesis of Allyl(halo)borabicyclononanes by Cycloaddition

6.1.37.7 Method 7: Diels-Alder Reactions of Allylboronates

6.1.37.8 Method 8: Diels-Alder Reactions of Vinylboranes

6.1.37.9 Method 9: α-Halo-ϒ,ϒ,ϒ-trichloropropylborane Derivatives by Additions to Vinylboranes and Vinylboronates

Applications of Product Subclass 37 in Organic Synthesis

6.1.37.10 Method 10: Cyclopropane Ring Formation via Hydroboration of Allylic Halides

6.1.38 Product Subclass 38: Trialkylboranes

M.Zaidlewicz and M.Krzeminski

6.1.38 Product Subclass 38: Trialkylboranes

Synthesis of Product Subclass 38

6.1.38.1 Method 1: Hydroboration of Alkenes

6.1.38.1.1 Variation 1: With Borane Complexes

6.1.38.1.2 Variation 2: With Monoalkylboranes

6.1.38.1.3 Variation 3: With Dialkylboranes

6.1.38.2 Method 2: Hydroboration of Dienes

6.1.38.2.1 Variation 1: With Borane Complexes

6.1.38.2.2 Variation 2: With Monoalkylboranes

6.1.38.3 Method 3: Hydroboration of Functional Derivatives of Alkenes

6.1.38.4 Method 4: Hydroboration of Alkynes

6.1.38.5 Method 5: Transmetalation

6.1.38.5.1 Variation 1: With Boron Halides and Tetrahaloborates

6.1.38.5.2 Variation 2: With Boron Alkoxides

6.1.38.6 Method 6: Isomerization

6.1.38.7 Method 7: Displacement

6.1.38.8 Method 8: Redistribution

6.1.38.9 Method 9: Pyrolysis

6.1.38.10 Method 10: Hydrogenation

6.1.38.11 Method 11: Organoborate Rearrangements

6.1.38.11.1 Variation 1: Homologation by Carbonylation

6.1.38.11.2 Variation 2: Homologation by Substituted Methyl Carbanions

6.1.38.11.3 Variation 3: Cyclization of α,α-Bis(dialkylboryl)-w-haloalkanes

6.1.38.12 Method 12: The Diels–Alder Reactions of Vinylic Dialkylboranes

Applications of Product Subclass 38

6.1.38.13 Method 13: Protonolysis

6.1.38.14 Method 14: Oxidation

6.1.38.14.1 Variation 1: Oxidation to Alcohols

6.1.38.14.2 Variation 2: Oxidation to Hydroperoxides

6.1.38.14.3 Variation 3: Oxidation to Aldehydes and Ketones

6.1.38.14.4 Variation 4: Oxidation to Acids

6.1.38.15 Method 15: Amination

6.1.38.15.1 Variation 1: Primary Amines

6.1.38.15.2 Variation 2: Secondary and Tertiary Amines

6.1.38.16 Method 16: Halogenolysis

6.1.38.16.1 Variation 1: Chlorinolysis

6.1.38.16.2 Variation 2: Brominolysis

6.1.38.16.3 Variation 3: Iodinolysis

6.1.38.17 Method 17: Sulfidation

6.1.38.18 Method 18: Transmetalation

6.1.38.18.1 Variation 1: Formation of Alkyl Selenides and Alkyl Tellurides

6.1.38.18.2 Variation 2: Formation of Alkylmercurials

6.1.38.18.3 Variation 3: Formation of Dialkylzincs from Trialkylboranes

6.1.38.19 Method 19: α-Bromination–Transfer

6.1.38.20 Method 20: Single-Carbon Insertion Reactions

6.1.38.20.1 Variation 1: Carbonylation of Trialkylboranes

6.1.38.20.2 Variation 2: Cyanidation

6.1.38.20.3 Variation 3: The α,α-Dichloromethyl Methyl Ether Reaction and Related Reactions

6.1.38.21 Method 21: α-Alkylation of Carbonyl Compounds, Nitriles, and α-Heterosubstituted Carbanions

6.1.38.21.1 Variation 1: Alkylation of α-Halogenated and α,α-Dihalogenated Carbonyl Compounds

6.1.38.21.2 Variation 2: Alkylation of α-Diazocarbonyl Compounds, and Other Diazo Compounds

6.1.38.21.3 Variation 3: Alkylation of α-Halogenated and α,α-Dihalogenated Nitriles

6.1.38.21.4 Variation 4: Alkylation of Other α-Heterosubstituted Carbanions

6.1.38.22 Method 22: Reaction of Organoborates with Electrophiles

6.1.38.22.1 Variation 1: Alkenyltrialkylborate Rearrangements

6.1.38.22.2 Variation 2: Trialkyl(alkynyl)borate Rearrangements

6.1.38.23 Method 23: Small Ring Formation

6.1.38.24 Method 24: Coupling of Alkyl Groups Attached to Boron

6.1.38.25 Method 25: The Cross-Coupling Reaction

6.1.38.25.1 Variation 1: Cross Coupling of Trialkylboranes

6.1.38.25.2 Variation 2: Carbonylative Cross Coupling of Trialkylboranes and Acyl-Alkyl Coupling

6.1.38.26 Method 26: Free-Radical Reactions

6.1.38.26.1 Variation 1: Conjugate Addition Reactions

6.1.38.26.2 Variation 2: Alkylation of 1,4-Quinones

6.1.38.26.3 Variation 3: Trialkylborane-Induced Reactions

6.1.38.26.4 Variation 4: Other Free-Radical Reactions

6.1.38.27 Method 27: 1,2-Addition to Carbonyl Compounds

6.1.38.27.1 Variation 1: Reduction of Carbonyl Compounds

6.1.38.27.2 Variation 2: The Boron-Wittig Reaction

6.1.38.27.3 Variation 3: Alkylation of Aryl Aldehyde Tosylhydrazones

6.1.38.28 Method 28: Formation of Di- and Trialkylborohydrides

6.1.38.28.1 Variation 1: Dialkylborohydrides

6.1.38.28.2 Variation 2: Trialkylborohydrides

6.1.39 Product Subclass 39: Tetraaryl- and Tetraalkylborates and Related Organometallic Compounds

D.E.Kaufmann and M.Köster

6.1.39 Product Subclass 39: Tetraaryl- and Tetraalkylborates and Related Organometallic Compounds

Synthesis of Product Subclass 39

6.1.39.1 Method 1: Tetraarylborates and Mixed Alkylarylborates from Aryl- lithiums, Grignard Reagents, or Related Compounds and Boranes

6.1.39.2 Method 2: Trialkylvinylborates from Organolithium Compounds and Boranes

6.1.39.2.1 Variation 1: Vinylation of Trialkylboranes

6.1.39.2.2 Variation 2: Alkylation of Vinylboranes

6.1.39.3 Method 3: Synthesis of Ethynyltriorganoborates from Metalated Alkynes and Boranes

6.1.39.3.1 Variation 1: From Alkali Acetylides or Acetylenic Grignard Compounds and Boranes

6.1.39.3.2 Variation 2: From Hydrotriorganoborates and Alkynes

6.1.39.4 Method 4: Synthesis of Tetraorganoborates from Alkyllithiums and Organoboranes

Applications of Product Subclass 39 in Organic Synthesis

6.1.39.5 Method 5: Formation of C-C Bonds

6.1.39.5.1 Variation 1: Arylations and Alkylations of Halides, Pseudohalides, and Heterocycles

6.1.39.5.2 Variation 2: Synthesis of Terminal Allenes

6.1.39.5.3 Variation 3: Arylations and Alkylations of Acid Halides

6.1.39.5.4 Variation 4: Synthesis of Biaryls

6.1.39.5.5 Variation 5: Synthesis of Alkyl-Substituted Aromatic Heterocycles

6.1.39.5.6 Variation 6: Addition/Rearrangement Reactions of Trialkyl(ethynyl)borates

6.1.39.6 Methods 6: Other Applications

6.1.40 Product Subclass 40: Carboranes and Metallacarboranes

F.Teixidor and C.Viñas

6.1.40 Product Subclass 40: Carboranes and Metallacarboranes

Synthesis of Product Subclass 40

6.1.40.1 Method 1: Synthesis of Monocarboranes

6.1.40.2 Method 2: Synthesis of Dicarboranes

6.1.40.3 Method 3: Synthesis of Anionic closo-Metallacarboranes

6.1.40.4 Method 4: Synthesis of Neutral closo-Metallacarboranes with Phosphine Ligands

6.1.40.5 Method 5: Synthesis of Forced exo-nido-Metallacarboranes with Sulfanyl- and Phosphine Ligands

6.1.40.6 Method 6: Synthesis of Neutral closo-Metallacarboranes with Allyl Ligands

6.1.40.7 Method 7: Synthesis of Neutral Charge-Compensated Sulfonium closo-Metallacarboranes

Applications of Product Subclass 40 in Organic Synthesis

6.1.40.8 Method 8: Stabilization of Carbenium Ions

6.1.40.8.1 Variation 1: Synthesis and Stabilization of the tert-Butyl Cation

6.1.40.9 Method 9: Icosahedral Borane Anions for Cation Precipitation

6.1.40.9.1 Variation 1: Precipitation of Speciality Cations

6.1.40.9.2 Variation 2: Anionic Carborane Clusters as Supramolecular Chemistry Models for Convex Surfaces

6.1.40.10 Method 10: Hydrogenation of Alkenes

6.1.40.10.1 Variation 1: Terminal Alkene Hydrogenation Using closo- and exo-nido-Rhodacarborane Clusters

6.1.40.10.2 Variation 2: Terminal Alkenes Hydrogenation Using Forced exo-nido- Monosulfanyl- and exo-nido-Monophosphinorhodacarboranes

6.1.40.10.3 Variation 3: Internal Alkenes by Hydrogenation Using closo- and exo-nido-Monosulfanylrhodacarboranes

6.1.40.11 Method 11: Kharasch Addition to Alkenes

6.1.41 Product Subclass 41: Boron-Containing Polymers

D.Gabel

6.1.41 Product Subclass 41: Boron-Containing Polymers

Synthesis of Product Subclass 41

6.1.41.1 Method 1: Polymerization by a Dehydration Reaction between Polyols and Boronic Acids

6.1.41.2 Method 2: Polymerization by Hydroboration

6.1.41.2.1 Variation 1: Of Dienes

6.1.41.2.2 Variation 2: Of Diynes

6.1.41.2.3 Variation 3: Of Dinitriles

6.1.41.2.4 Variation 4: Of Alkenes by Bromoborane

6.1.41.3 Method 3: Polymerization by Allylboration of Dinitriles

6.1.41.4 Method 4: Polymerization by Chloroboration of Alkynes

6.1.41.5 Method 5: Polymerization by Alkoxyboration of Diisocyanates

6.1.41.6 Method 6: Ziegler–Natta Polymerization of Boron-Containing Alkenes

6.1.41.7 Method 7: Polymerization by Complex Formation between Boranes and Amines

6.1.41.8 Method 8: Modification of Boron-Containing Polymers

Applications of Product Subclass 41 in Organic Synthesis

6.1.41.9 Method 9: Modification of Non-Boron-Containing Polymers by Hydroboration

6.1.41.10 Method 10: Polymers by Electropolymerization of Boron-Containing Monomers

6.1.41.11 Method 11: Removal of Boron from Polymers

Keyword Index

Author Index

Abbreviations

Introduction

D. E. Kaufmann

This volume describes the organometallic and organic chemistry of boron. Despite covering just a single element, an extremely broad spectrum of chemistry is discussed within. As for other volumes of Science of Synthesis, the authors are experts in their respective fields and have covered the most important developments selectively and critically. Applications of the compounds synthesized are emphasized and, wherever appropriate, experimental procedures are provided in the text.

Old manuscripts indicate that the Arabs and Persians knew of the mineral borax (sodium tetraborate decahydrate), the first and still the most important natural boron source, over 2000 years ago. Boron oxide has been detected in Chinese enamels from the 4th century B.C. Elemental boron was discovered as a gray powder independently in 1808 by Gay-Lussac and Thenard in France, and by Davy in England as the main reduction product of boric acid by means of potassium. Davy suggested the name “boron”, formed from the first syllable from borax and the second from carbon, recognizing important similarities with the latter. The green flame of burning triethylborane, the first representative of the group of organoboron compounds, was reported by Frankland and Duppa in 1860. It then took 50 more years before Stock,[1] working on this task during 1912–36, and later Lipscomb (Nobel Prize 1976)[2] investigated the synthesis, structures, and bonding properties of the novel class of hydroboranes. Subsequently, hydridopolyborates were discovered, followed by heteroboranes, with carboranes being the most important subclass of the latter. The important field of organic synthesis via organoboranes was, broadly, developed first by Brown (Nobel Prize 1979)[3] and co-workers since the middle of the 20th century, strongly accelerated by the discovery of the hydroboration reaction of alkenes and alkynes in 1956.[4] In 1959, the first diastereoselective,[5] and 2 years later a highly enantio-selective,[6] hydroboration reaction by means of chiral, terpene-based hydroboranes developed by Brown and Zweifel marked the beginning of practical asymmetric synthesis.

Boron reagents have become very important standard tools for the synthetic chem-ist[7, 8] because boron compounds combine a unique mixture of interesting properties such as Lewis acidity and facile though highly stereoselective oxidizability.[9] The boron atom is slightly larger than carbon. All trivalent boron compounds are planar, whereas tetra-valent boron compounds assume tetrahedral or nearly tetrahedral geometry. The B-C bond (~323 kJ•mol–1)[10,11] is not much weaker than a C-C bond (~358 kJ•mol–1); this situation is also reflected by similar bond lengths (B-C ~156 pm). These two classes of compounds are closely related; neutral tricoordinate boron compounds such as trimethylbo-rane are isoelectronic with carbenium ions such as the corresponding tert-butyl cation, whereas boronic acids [R1B(OH)2] are isoelectronic with carboxylic acids, and negatively charged tetracoordinate borates such as the borohydride anion are isoelectronic with neutral hydrocarbons such as methane.[12]

Boron forms even stronger bonds with nitrogen, oxygen, fluorine, and chlorine. The B-H bond (~375 kJ•mol–1) is also slightly weaker than the C-H bond. By means of three-center bonds, monoorganohydroboranes and diorganohydroboranes form dimers, which always display hydride bridges rather than alkyl bridges, as illustrated in ▶ Scheme 1.[13–15]

▶ Scheme 1 Hydride Bridging in Monoorganohydroboranes and Diorganohydroboranes[13–15]

In contrast to hydroboranes, trialkylboranes are monomeric, which may be traced to hy-perconjugation with the alkyl substituents. In organoboranes, the B—C bond has largely single σ-bond character. Electron-rich π-systems such as vinyl or aryl groups provide the adjacent B—C bond with partial double-bond character. In small-ring boron heterocycles such as the 2π-systems, 1H-borirenes (e.g., 1), structural and spectroscopic data point to extensive π-electron delocalization.[16] The four-membered dihydrodiboretes exist in two isomers, a planar 1,2-dihydro-1,2-borete 2 with two localized π-electrons and a “butterfly” shaped 1,3-dihydro-1,3-borete 3 with delocalized π-electrons.[17] The 4π-antiaromatic 1H-borole is labile, even in perarylated form 4 (▶ Scheme 2).[18]

▶ Scheme 2 Boron Heterocycles[16–18]

Substituents with electron lone pairs act similarly while the strength of the boron—het-eroatom π-bonds decreases in the order nitrogen > fluorine > oxygen > sulfur > chlorine. All mesomeric interactions lead to a distinct stabilization of the particular organoboranes.