Organic Redox Chemistry E-Book
133,99 €
Mehr erfahren.
- Herausgeber: Wiley-VCH GmbH
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
Organic Redox Chemistry
Explore the most recent advancements and synthesis applications in redox chemistry
Redox chemistry has emerged as a crucial research topic in synthetic method development. In Organic Redox Chemistry: Chemical, Photochemical and Electrochemical Syntheses, some key researchers in this field, including editors Dr. Frédéric W. Patureau and the late Dr. Jun-Ichi Yoshida, deliver an insightful exploration of this rapidly developing topic.
This book highlights electron transfer processes in synthesis by using different techniques to initiate them, allowing for a multi-directional perspective in organic redox chemistry. Covering a wide array of the important and recent developments in the field, Organic Redox Chemistry will earn a place in the libraries of chemists seeking a one-stop resource that compares chemical, photochemical, and electrochemical methods in organic synthesis.
Sie lesen das E-Book in den Legimi-Apps auf:
Seitenzahl: 366
Veröffentlichungsjahr: 2021
Ähnliche
Table of Contents
Cover
Title Page
Copyright
Biography
Preface
1 Chemical Oxidative C–C Bond Formation
1.1 Introduction
1.2 Oxidative Aryl–Alkenyl Bond Formation
1.3 Oxidative Aryl–Aryl Bond Formation
1.4 Oxidative Aryl–Alkynyl Bond Formation
1.5 Oxidative C–C Bond Formation at Csp3 Center
1.6 Conclusion
References
2 Electrochemical Oxidative C–C Bond Formation
2.1 Electrochemical Oxidative Aryl–Aryl Cross‐Coupling Reaction
2.2 Electrochemical Oxidative Benzyl–Aryl Cross‐Coupling Reaction
2.3 Electrochemical Oxidative Arylation of Olefins
2.4 Electrochemical Oxidative Arylation of Alkynes
2.5 Electrochemical Oxidative Cross‐Dehydrogenative Coupling of C(sp3)H and C(sp2)H Bonds
References
3 Fundamentals of Photochemical Redox Reactions
3.1 Introduction: A Brief History of Photochemistry
3.2 Photochemistry: Background and Theory
3.3 Photoredox Catalysis
3.4 Photochemistry of Electron Donor–Acceptor Complexes
3.5 Concluding Thoughts
Suggested Additional Reading
References
4 C–H Bond Functionalization with Chemical Oxidants
4.1 Introduction
4.2 Metal‐Based Oxidants and Other Inorganic Oxidants
4.3 Organic Oxidants
4.4 Internal Oxidants (DGox)
4.5 Use of O2 as an Oxidant
4.6 Dehydrogenative Couplings with No Oxidant at All
4.7 Conclusion
References
Note
5 Electrochemical Reductive Transformations
5.1 General Characteristics of Electrochemical Reactions
5.2 Mechanism of Organic Electrochemical Reductions
5.3 Characteristics of Organic Electrochemical Reductions
5.4 Electroauxiliaries
5.5 Reaction Pattern of Organic Electrochemical Reductions
5.6 Electrochemically Generated Reactive Species
5.7 Advanced Methodology for Electrochemical Reductive Transformations
5.8 Conclusions
References
6 Electrochemical Redox‐Mediated Polymer Synthesis
6.1 Introduction
6.2 Synthesis of Conducting Polymers by Electrochemical Redox
6.3 Post‐Functionalization of Conducting Polymers by Electrochemical Redox
6.4 Synthesis of Nonconjugated Polymers by Electrochemical Redox
6.5 Conclusion
References
7 Chemical Paired Transformations
7.1 Introduction
7.2 Direct Arylation of Arenes with Aryl Halides
7.3 Electron‐Catalyzed Cross‐Coupling Reactions of Aryl Halides
7.4 Conclusions
References
8 Photochemical Paired Transformations
8.1 Introduction
8.2 Basic Concepts for Photochemical Hydrogen Atom Transfer (HAT) Process
8.3 Asymmetric Radical Functionalization Associated with Direct HAT by Photocatalysts
8.4 Asymmetric Radical Functionalization Associated with Indirect HAT Triggered by Photocatalysis
8.5 Summary and Outlook
References
9 Paired Electrolysis
9.1 Introduction
9.2 Paired Electrolysis for Sequential Reactions at both Electrodes
9.3 Paired Electrolysis with Two Different Reactions at both Electrodes
9.4 Paired Electrolysis for Generation of Two Intermediates to Afford a Final Product by the Sequential Reaction
9.5 Conclusion
References
Index
End User License Agreement
List of Tables
Chapter 3
Table 3.1 Typical time scales of photophysical processes for organic molecul...
Table 3.2 Absorption characteristics of common organic functional groups.
Table 3.3 Typical properties of EDA complexes that undergo ISET and OSET.
Chapter 5
Table 5.1 Reduction potentials of aromatic mediators for indirect cathodic r...
List of Illustrations
Chapter 1
Scheme 1.1 Overall redox‐neutral CC bond formation (a) vs. oxidative CC bo...
Scheme 1.2 General mechanism of palladium‐catalyzed overall redox‐neutral Mi...
Scheme 1.3 General mechanism of palladium‐catalyzed oxidative Mizoroki–Heck ...
Scheme 1.4 Pd(OAc)
2
/bis(sulfoxide)‐catalyzed oxidative Mizoroki–Heck reactio...
Scheme 1.5 Pd(I
i
Pr)(OTs)‐catalyzed oxidative Mizoroki–Heck reaction of unact...
Scheme 1.6 Palladium‐catalyzed enantioselective redox‐relay oxidative Mizoro...
Scheme 1.7 Palladium‐catalyzed enantioselective redox‐relay oxidative Mizoro...
Scheme 1.8 General reaction scheme and mechanism of palladium‐catalyzed Fuji...
Scheme 1.9 Rhodium(II)‐catalyzed Fujiwara–Moritani reaction of simple arenes...
Scheme 1.10 Palladium/hydroxypyridine‐catalyzed Fujiwara–Moritani reaction o...
Scheme 1.11 Carboxylic‐acid‐directed ortho‐selective Fujiwara–Moritani react...
Scheme 1.12 Cp*Rh(III)‐catalyzed ortho‐selective Fujiwara–Moritani reaction ...
Scheme 1.13 Palladium/silver‐catalyzed meta‐selective Fujiwara–Moritani reac...
Scheme 1.14 Rhodium‐catalyzed meta‐selective Fujiwara–Moritani reaction assi...
Scheme 1.15 Palladium‐catalyzed para‐selective Fujiwara–Moritani reaction as...
Scheme 1.16 General mechanisms of overall redox‐neutral biaryl cross‐couplin...
Scheme 1.17 Oxidative C–H/C–M biaryl coupling of electron‐rich indole, thiaz...
Scheme 1.18 Nickel‐catalyzed oxidative C–H/C–M biaryl coupling of relatively...
Scheme 1.19 Oxidative C–H/C–M biaryl coupling of benzene derivatives with as...
Scheme 1.20 Pd/
o
‐chloranil‐catalyzed oxidative C–H/C–M biaryl coupling of hi...
Scheme 1.21 Oxidative biaryl coupling via decarboxylative C–H arylation.
Scheme 1.22 Oxidative C–H/C–H biaryl coupling with simple benzene and pyridi...
Scheme 1.23 Oxidative C–H/C–H biaryl coupling with relatively activated hete...
Scheme 1.24 Oxidative C–H/C–H biaryl couplings promoted by transition metals...
Scheme 1.25 Approaches to arylacetylenes via aryl–alkynyl coupling.
Scheme 1.26 Copper‐, nickel‐, and palladium‐catalyzed oxidative aryl–alkynyl...
Scheme 1.27 Gold‐ and palladium‐catalyzed oxidative aryl–alkynyl couplings o...
Scheme 1.28 N,N‐bidentately coordinating group‐promoted oxidative aryl–alkyn...
Scheme 1.29 General mechanism of cross‐dehydrogenative coupling (CDC) of C
sp
Scheme 1.30 Enantioselective CDC reactions of tetrahydroisoquinoline derivat...
Scheme 1.31 CDC reactions of benzyl‐ and allyl‐type substrates.
Scheme 1.32 CDC reaction of simple alkane.
Scheme 1.33 General mechanism of oxidative coupling of two carbonyl compound...
Scheme 1.34 Cu(II)‐, Fe(III)‐, Ce(IV)‐, and V(V)‐mediated oxidative cross‐co...
Scheme 1.35 Oxidative decarboxylative coupling of malonic acid half esters. ...
Scheme 1.36 Directed Fujiwara–Moritani‐type reaction at unactivated C
sp
3
–H. ...
Scheme 1.37 Bidentately coordinating group directed oxidative CC bond forma...
Chapter 2
Scheme 2.1 Overview of some anodic C–C homo‐coupling reactions.
Scheme 2.2 Potential products for an anodic, electrochemical C–C coupling re...
Scheme 2.3 Concept of “radical‐cation pool” method.
Scheme 2.4 Overview of anodic C–C cross‐coupling reactions between phenols a...
Scheme 2.5 Overview of anodic CC bond formations between phenols and hetero...
Scheme 2.6 Overview of anodic CC bond formations using anilines or naphthyl...
Scheme 2.7 Benzyl–aryl cross‐coupling by anodic activation in HFIP.
Scheme 2.8 Benzyl–aryl cross‐coupling by stabilized “cation pool” method....
Scheme 2.9 Electrochemically assisted Heck reactions.
Scheme 2.10 Mn
3+
‐mediated intramolecular coupling reaction.
Scheme 2.11 Anodic conversions of phenols with olefins.
Scheme 2.12 Regio‐ and stereo‐selective synthesis of aryl and olefin.
Scheme 2.13 Intramolecular anodic olefin coupling reaction.
Scheme 2.14 Electrochemical intramolecular C–H/N–H [3+2] annulation mediated...
Scheme 2.15 Electrochemical synthesis of C3‐fluorinated oxindoles.
Chapter 3
Scheme 3.1 Early photochemical quinone reductions studied by Klinger.
Scheme 3.2 Condensation of nitrobenzene and ethanol to form 2‐methylquinolin...
Scheme 3.3 First catalytic photoredox reaction for the reduction of sulfoniu...
Scheme 3.4 Early photoredox reductions detailed by Pac and Fukuzumi.
Scheme 3.5 Photoredox reactions of aryl diazonium salts developed by Cano‐Ye...
Scheme 3.6 Photoredox [2+2] enone cycloadditions reported by Yoon and cowork...
Scheme 3.7 MacMillan's report on the enantioselective alkylation of aldehyde...
Scheme 3.8 Photoredox dehalogenation reactions developed by Stephenson and c...
Scheme 3.9 Carbon–sulfur bond formation as a result of EDA complex formation...
Figure 3.1 Electromagnetic spectrum, with a focus on regions associated with...
Figure 3.2 A Jablonski diagram depicted in two ways. On the left, electronic...
Figure 3.3 Potential energy surfaces for electron transfer in the nonadiabat...
Figure 3.4 Simplified reaction coordinate diagrams used to describe Marcus t...
Figure 3.5 General instrument layout for absorption spectroscopy (a) and exa...
Figure 3.6 General instrument layout for emission spectroscopy (a) and an ex...
Figure 3.7 General instrument layout for transient absorption (a) and exampl...
Figure 3.8 Examples of cyclic voltammograms for reversible, quasireversible,...
Figure 3.9 General design of a batch reactor (a) and a flow reactor (b).
Figure 3.10 Generalized photoredox catalytic cycles proceeding through oxida...
Figure 3.11 Common photoredox catalysts based on Ru, Ir, and Cu complexes.
Scheme 3.10 Ir(III) photocatalyzed hydrodehalogenation of an aryl iodide....
Scheme 3.11 Visible light–mediated aza‐Henry reaction of an
N
‐aryl tetrahydr...
Scheme 3.12 Oxytrifluoromethylation of styrene using an Ir(III) photocatalys...
Scheme 3.13 Decarboxylative fluorination with metal photocatalysts.
Scheme 3.14 ATRA catalyzed by a Cu(I) photocatalyst.
Scheme 3.15 Oxidative amine functionalization by an organic photocatalyst....
Figure 3.12 Redox properties of organic excited‐state oxidants. Since many o...
Scheme 3.16 Anti‐Markovnikov hydroamination of olefins via radical cation in...
Scheme 3.17 Photoredox‐catalyzed C–H amination reported by Nicewicz.
Scheme 3.18 Photocatalytic oxygenation of benzene to form phenol.
Scheme 3.19 Oxidation of benzylic epoxides and cycloaddition with DMAD to fo...
Scheme 3.20 General scheme (left) and mechanism (right) of O‐ATRP.
Figure 3.13 Redox properties of organic excited‐state reductants. Since many...
Scheme 3.21 Selective functionalization of aryl‐halides using phenothiazine ...
Scheme 3.22 Alkylation of trifluoromethyl arenes through defluorination usin...
Scheme 3.23 Trifluoromethylation of alkenes using a dihydrophenazine PC.
Scheme 3.24 Aryl C–N coupling reactions employing dihydrophenazine and pheno...
Scheme 3.25 Aryl C–S couplings using a phenoxazine PC.
Scheme 3.26 Hydrodehalogenation of aryl halides with PDI photocatalysts.
Scheme 3.27 Reductive coupling of aryl halides with an excited radical anion...
Scheme 3.28 Organocatalyzed visible light–mediated photoredox Birch reductio...
Figure 3.14 Highly oxidizing excited organic radical cations. E
ox
= E
°
(...
Figure 3.15 General diagram showing the association of a donor and acceptor ...
Scheme 3.29 An example of EDA complex reactivity for coupling pyrroles and a...
Scheme 3.30 An example of EDA complex reactivity for enantioselective‐coupli...
Scheme 3.31 A reaction reported by Melchiorre and coworkers in 2015 that pro...
Scheme 3.32 A C–S coupling reaction enabled by EDA complex reactivity report...
Scheme 3.33 An example from Paixão and coworkers in 2015 employing a sacrifi...
Scheme 3.34 Reaction reported in 2017 by Chen and coworkers that employs bot...
Scheme 3.35 Reported by Leonori and coworkers in 2015, this reaction employs...
Scheme 3.36 This reaction, reported by Aggarwal and coworkers in 2017, emplo...
Scheme 3.37 An example from Bosque and Bach in 2019 of an EDA complex reacti...
Scheme 3.38 Enantioselective reductive dehalogenation reported by Hyster and...
Chapter 4
Scheme 4.1 Ag(I) and Cu(II) oxidants.
Scheme 4.2 Radical Co(II)/Co(III) cross‐dehydrogenative CO bond formation b...
Scheme 4.3 You's dehydrogenative heterocyclic CC bond formation.
Scheme 4.4 Song's cocatalyzed dehydrogenative amination of benzamides.
Scheme 4.5 Lei's oxidative C(sp
3
)–H/N–H carbonylation reaction.
Scheme 4.6 Cheng's dehydrogenative reaction with benzamides and boronic acid...
Scheme 4.7 Glorius's RhCp*‐catalyzed dehydrogenative allylic arylation.
Scheme 4.8 Blakey's RhCp*‐catalyzed dehydrogenative CO bond formation.
Scheme 4.9 You's dehydrogenative
hetero
biaryl synthesis.
Scheme 4.10 You and Song's arylated quinone synthesis.
Scheme 4.11 Shi's amino‐acid functionalization through Pd‐catalyzed C(sp
3
)–H...
Scheme 4.12 Yu's γ and δ C–H arylation methods of amino alkanes.
Scheme 4.13 Duan's reaction: Ag(I)‐mediated dehydrogenative phosphole synthe...
Scheme 4.14 Ritter's oxidative cyanation of aromatic CH bonds.
Scheme 4.15 Engle and Liu's dehydrogenative Fujiwara‐like diene synthesis....
Scheme 4.16 Lei's cross‐dehydrogenative amination with some azole derivative...
Scheme 4.17 Organic peroxides and quinones.
Scheme 4.18 Ni(II/III)‐catalyzed C(sp
3
)–C(sp
3
) dehydrogenative coupling from...
Scheme 4.19 Dehydrogenative thioether formation by Lei.
Scheme 4.20 Lei's C(sp
3
)–H arylation of THF.
Scheme 4.21 Dehydrogenative acridone synthesis from Lei.
Scheme 4.22 Li and Song's
spiro
‐[4,5]trienone synthesis.
Scheme 4.23 Lei's Cu/Ni/Ag cocatalyzed oxidative‐Sonogashira‐like reaction....
Scheme 4.24 Siegel's phenol synthesis with unusual phthaloyl peroxide.
Scheme 4.25 Lei and Luo's C–H allylation of ketones.
Scheme 4.26 Pumera's recent Cu(II)‐catalyzed CDC reaction with DDQ.
Scheme 4.27 Possible mechanisms of DDQ‐mediated C–H cleavage according to Li...
Scheme 4.28 Lei and Chiang's DDQ‐ and TBN‐catalyzed aerobic C(sp
3
)N bond fo...
Scheme 4.29 Qing's oxidative C–H difluoromethylation of some heterocycles....
Scheme 4.30 DG
ox
and internal oxidants.
Scheme 4.31 Fagnou's DG
ox
‐mediated RhCp*‐catalyzed isoquinolone synthesis....
Scheme 4.32 General mechanism.
Scheme 4.33 Glorius's bis‐isoquinolone synthesis.
Scheme 4.34 Glorius's isoquinolone synthesis: very low reaction temperature ...
Scheme 4.35 The coupling partner inside the DG
ox
by Glorius and coauthors.
Scheme 4.36 Postulated mechanism.
Scheme 4.37 Glorius's intramolecular RhCp*‐catalyzed C–H amidation reaction....
Scheme 4.38 Proposed mechanism for Glorius's intramolecular RhCp* catalyzed ...
Scheme 4.39 O
2
‐mediated dehydrogenative phenothiazination of phenols.
Scheme 4.40 O
2
‐mediated copper‐catalyzed quinone intermediate generation fro...
Scheme 4.41 White's O
2
‐mediated dehydrogenative allylic amination method....
Scheme 4.42 Proposed mechanism for White's O
2
mediated dehydrogenative allyl...
Scheme 4.43 O
2
‐mediated oxazole synthesis by Chiba and Jiao. (a) Copper‐cata...
Scheme 4.44 O
2
‐mediated oxazole synthesis from amines and alkynes from Jiao....
Scheme 4.45 Proposed mechanism for the O
2
mediated oxazole synthesis from am...
Scheme 4.46 O
2
‐mediated α‐keto amide synthesis of Jiao.
Scheme 4.47 Proposed mechanism for the O
2
mediated α‐keto amide synthesis of...
Chapter 5
Figure 5.1 Difference between (a) chemical reaction and (b) electrochemical ...
Figure 5.2 Elementary processes of electrode reaction.
Figure 5.3 Regioselective cathodic dechlorination.
Figure 5.4 Stereoselective reduction based on orientation of substrate on th...
Figure 5.5 Anodic shift of reduction potential owing to protonation.
Figure 5.6 Anodic shift of reduction potential owing to coordination with Le...
Figure 5.7 Principle of indirect electroreduction using mediator. (a) Direct...
Figure 5.8 Current‐potential curve at direct and indirect electroreduction....
Figure 5.9 Electrosynthesis using Co(III) complex, Vitamin B12 as mediator....
Figure 5.10 Homo‐coupling of aryl halide using Pd(0) complex.
Figure 5.11 Electrogenerated base of hindered azobenzene.
Figure 5.12 Reactive anion derived from electrogenerated base (EGB) (Q
+
...
Chapter 6
Scheme 6.1 Electrochemical doping and dedoping behavior of polythiophene.
Scheme 6.2 Plausible mechanism for the anodic electropolymerization of heter...
Figure 6.1 General design of electropolymerizable aromatic monomers with dit...
Figure 6.2 Electrochemical copolymerization of zinc‐porphyrin and 4,4′‐bipyr...
Scheme 6.3 Electroreductive synthesis of
PPV
from
p
‐xylene derivative.
Figure 6.3 Electrochemically synthesized polysilanes and derivatives.
Scheme 6.4 Anodic chlorination of P3MT.
Figure 6.4 Electrochemical halogenation of fluorene‐containing conjugated po...
Scheme 6.5 Segment‐selective anodic chlorination of rod–rod block copolymer....
Scheme 6.6 Cathodic hydrogenation of ketone moiety in the polyfluorene backb...
Scheme 6.7 Paired electrolysis of fluorene‐containing conjugated polymer....
Scheme 6.8 Electrochemical fluorination of polyaniline via the CRS method.
Scheme 6.9 Intramolecular cyclization of binaphthol moiety to give
peri
‐xant...
Scheme 6.10 Polymerization of [Ru(dvbpz)(bpz)
2
] by cathodic reduction.
Figure 6.5 Recently developed polymerization methodologies to afford nonconj...
Chapter 7
Scheme 7.1 Transition metal-catalyzed cross‐coupling reaction of aryl halide...
Scheme 7.2 S
RN
1 reaction of aryl halides.
Scheme 7.3 Electron‐catalyzed substitution reaction of aryl halides.
Scheme 7.4 Biaryl synthesis from aryl halides through homolytic aromatic sub...
Scheme 7.5 Direct arylation of N‐heteroarenes with aryl halides.
Scheme 7.6 Direct arylation of benzene derivatives with aryl halides.
Scheme 7.7 Direct arylation through a base‐promoted homolytic aromatic subst...
Scheme 7.8 Direct arylation initiated by photoirradiation or
tert
‐butoxy rad...
Scheme 7.9 Regiochemistry in the direct arylation.
Scheme 7.10 Other base‐promoted arylation reactions.
Scheme 7.11 Electron‐catalyzed cross‐coupling reaction of aryl halides with ...
Scheme 7.12 Mechanism of the electron‐catalyzed Grignard cross‐coupling reac...
Scheme 7.13 Acceleration of the Grignard cross‐coupling reaction by addition...
Scheme 7.14 Radical clock reaction in the Grignard cross‐coupling reaction....
Scheme 7.15 Competition reaction between aryl halides in the Grignard cross‐...
Scheme 7.16 Grignard cross‐coupling reactions.
Scheme 7.17 Electron‐catalyzed cross‐coupling reaction of aryl and alkenyl h...
Scheme 7.18 Other electron‐catalyzed cross‐coupling reactions.
Chapter 8
Scheme 8.1 Concept 1 where PC* =
˙
A highlighted in the present chapter....
Scheme 8.2 Concept 2 where PC* ≠
˙
A highlighted in the present chapter....
Scheme 8.3 Introduction of aldoxime functionality onto C(sp
3
)H bonds.
Scheme 8.4 Giese‐type reaction of C(sp
3
)H bonds.
Scheme 8.5 Giese‐type reaction of C(sp
3
)H bonds by decatungstate.
Scheme 8.6 Decatungstate photocatalysis.
Scheme 8.7 Arylation of aliphatic C(sp
3
)H bonds.
Scheme 8.8 Asymmetric aldol reaction of aldehydes generated through photocat...
Scheme 8.9 Enantioselective construction of quaternary carbon center through...
Scheme 8.10 Photoredox‐catalyzed mild HLF‐type reaction.
Scheme 8.11 Mild HLF‐type reaction of sulfonamides.
Scheme 8.12 Amide‐directed photocatalytic CC bond formation at aliphatic C(...
Scheme 8.13 Alkoxy radical–mediated photocatalytic allylation of alkenylatio...
Scheme 8.14 Alcohol‐directed photocatalytic heteroarylation of aliphatic C(s...
Scheme 8.15 Alkoxy radical–mediated asymmetric alkylation of aliphatic C(sp
3
Scheme 8.16 Amide‐directed asymmetric alkylation of aliphatic C(sp
3
)H bonds...
Chapter 9
Figure 9.1 Three types of paired electrolysis.
Figure 9.2 Monsanto process for the synthesis of adiponitrile from acrylonit...
Figure 9.3 Sequential oxidation and reduction of oximes by electrochemical r...
Figure 9.4 The homo coupling reaction of imidazopyridine‐based heterocycles ...
Figure 9.5 Electrosynthesis of nitrosobenzene from nitrobenzene by using the...
Figure 9.6 Anodic oxidation followed by cathodic reduction of benzylamine in...
Figure 9.7 Anodic oxidation followed by the cathodic reduction of the phenol...
Figure 9.8 Formation of two different products at both electrodes using an u...
Figure 9.9 Paired polymer electrolysis on both electrodes in an undivided ce...
Figure 9.10 Paired electrolysis in an industrial scale.
Figure 9.11 Synthesis of two different products in a divided cell.
Figure 9.12 Self‐supported paired electrolysis for anodic oxidation of 1‐phe...
Figure 9.13 Generation of two intermediates such as alkoxycarbenium ion and ...
Figure 9.14 Generation of two intermediates such as alkoxycarbenium ion and ...
Figure 9.15 Generation of two intermediates in an undivided cell followed by...
Figure 9.16 Paired electrolysis of bromination in Prins cyclization involvin...
Figure 9.17 Paired electrolysis in an undivided cell via the carbon–carbon b...
Figure 9.18 Oxytrifluoromethylation by using a paired electrolysis.
Figure 9.19 Sequential Diels–Alder reaction promoted by paired electrolysis ...
Figure 9.20 Synthesis of homoallylic alcohol by using a divided cell. Thus‐a...
Figure 9.21 Paired electrochemical synthesis of the metal catalyst in flow....
Figure 9.22 Electrochemical generation of two intermediates in a microreacto...
Guide
Cover
Table of Contents
Title Page
Copyright
Biography
Preface
Begin Reading
Index
End User License Agreement
Pages
iv
xi
xiii
xiv
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
225
226
227
228
229
230
231
232
Organic Redox Chemistry
Chemical, Photochemical and Electrochemical Syntheses
Edited byJun–Ichi YoshidaFrédéric W. Patureau
Editors
Prof. Jun‐Ichi Yoshida
Kyoto University
School of Engineering
Nishikyo‐ku
Kyoto University
606‐8510 Kyoto
Japan
Prof. Frédéric W. Patureau
Institut für Organische Chemie
RWTH Aachen University
Landoltweg 1
52074 Aachen
Germany
Cover
Cover Image: © Netfalls Remy Musser/Shutterstock
All books published by WILEY‐VCH are carefully produced. Nevertheless, authors, editors, and publisher do not warrant the information contained in these books, including this book, to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate.
Library of Congress Card No.:
applied for
British Library Cataloguing‐in‐Publication Data
A catalogue record for this book is available from the British Library.
Bibliographic information published by the Deutsche Nationalbibliothek
The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the Internet at <http://dnb.d-nb.de>.
© 2022 WILEY‐VCH GmbH, Boschstr. 12, 69469 Weinheim, Germany
All rights reserved (including those of translation into other languages). No part of this book may be reproduced in any form – by photoprinting, microfilm, or any other means – nor transmitted or translated into a machine language without written permission from the publishers. Registered names, trademarks, etc. used in this book, even when not specifically marked as such, are not to be considered unprotected by law.
Print ISBN: 978‐3‐527‐34487‐1
ePDF ISBN: 978‐3‐527‐81570‐8
ePub ISBN: 978‐3‐527‐81568‐5
oBook ISBN: 978‐3‐527‐81567‐8
Biography
Jun‐Ichi Yoshida (1952–2019)
Jun‐Ichi Yoshida was born in Osaka, Japan, on 13 November 1952. He graduated from Kyoto University in 1975 and obtained his PhD under the supervision of Professor Makoto Kumada in 1981. He joined the faculty at Kyoto Institute of Technology as an Assistant Professor of the research group of Professor Nariyoshi Kawabata in 1979. In the meantime, he visited the University of Wisconsin in 1982–1983, where he joined the research group of Professor Barry M. Trost. In 1985, he moved to the research group of Professor Sachihiko Isoe of Osaka City University, wherein he was promoted to an Associate Professor position in 1992. He returned to Kyoto University as a full professor in 1994 and served there until 2018. After his retirement, he was appointed as President of the National Institute of Technology, Suzuka College, and the supervisor of the research program “Innovative reactions” of Japan Science and Technology Agency. At the same time, he was chairperson of the Group for Research on Automated Flow and Microreactor Synthesis (GRAMS), the Kinka Chemical Society, Japan, since its founding in 1996. He served also as president of the Society of Synthetic Organic Chemistry, Japan, from 2017 to 2019.
His research interests included flash chemistry, integrated organic synthesis, and organic electron transfer chemistry. He received numerous awards, including the Progress Award of Synthetic Organic Chemistry, Japan (1987), the Chemical Society of Japan Award for Creative Work (2001), the Nagoya Silver Medal of Organic Chemistry (2006), the Humboldt Research Award (2007), the Dougane Award (2010), the Green and Sustainable Chemistry Award (2010), the Ta‐shue Chou Lectureship Award (2013), the Chemical Society Japan Award (2013), the Manuel. M. Baizer Award (2014), and the Medal of Honor with Purple Ribbon (2015). His tremendous passion toward chemical research, education, and society lasted until the day before he passed away on 14 September 2019.
13th October 2020
Toshiki Nokami
Preface
“Because this method [Metal‐ and chemical‐oxidant‐free C–H/C–H cross‐coupling of aromatic compounds: the use of radical‐cation pools] consists of two sequential steps, namely the generation and accumulation of a radical cation of an aromatic compound under oxidative conditions and then the coupling of the radical cation with another aromatic substrate under nonoxidative conditions, nonselective oxidation of the starting materials and oxidation of the products are avoided.” (The Yoshida scenario for a controlled dehydrogenative hetero‐coupling reaction, T. Morofuji, A. Shimizu, J. Yoshida, Angew. Chem. Int. Ed. 2012, 51, 7259). The problem presented in this milestone paper and its solution are characteristic of the quest for (radical) hetero‐cross‐dehydrogenative couplings.
This present book is dedicated to its original editor, the late Prof. Yoshida, and his achievements in the field of the title topic.
The late Prof. Yoshida, originally the principal and only editor of this book, sadly passed away in 2019, leaving this important Organic Redox Chemistry book project unfinished. As one of its authors, I accepted in November 2019 to finish assembling it, as a tribute to his inspiring scientific achievements. In his memory, I kept as much as possible the original structure laid out by Prof. Yoshida. I had to make nevertheless some necessary adjustments, such as in the order of chapters and their contents. Moreover, in view of these exceptional circumstances, much topical freedom was given to all authors. Some chapters had already been received by Prof. Yoshida before his passing. Some were received in the winter and spring of 2020. The very last chapter to be submitted, which I absolutely wanted for this book, was received in September 2020. I thank all authors for their expert contributions and for their patience. It is now time to move forward.
Beyond the tribute to Prof. Yoshida, one of the reasons I volunteered to finish assembling this book project is that I very much agree with its topical importance and scope. This also coincided well with my recent appointment as Professor at the RWTH Aachen University as well as with the general objectives of my ongoing ERC project (“2O2ACTIVATION”: Development of Direct Dehydrogenative Couplings mediated by Dioxygen, grant agreement 716136). I would like to thank at this point Dr. Rajaa Benchouaia and M. Sc. Pooja Vemuri from our research group here in Aachen for their editorial assistance.
The broad and inclusive title Organic Redox Chemistry, Chemical, Photochemical, and Electrochemical Syntheses is the original one proposed by Prof. Yoshida. The chapters herein highlight the increasing importance of redox aspects in numerous classes of organic reactions. Indeed, the latter are often governed – at least to some degree – by redox events. Where did the electron go? Its displacement can change to a stark degree the reactivity and life times of key reaction intermediates, as well as their relative philicity (electrophilicity or nucleophilicity). In other words, redox events often control reactivity and selectivity in chemical reactions. Understanding and controlling those processes will thus continue to be at the heart of twenty first century synthetic methodology. I hope the present collection of chapters will provide the reader, both novice and expert, with a vision into this imminent future, as well as with some inspiration to shape it.
13 October 2020
Frédéric W. Patureau
RWTH Aachen University
1Chemical Oxidative CC Bond Formation
Koji Hirano
Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Yamadaoka 2‐1, Suita, Osaka, 565‐0871, Japan
1.1 Introduction
Efficient and selective CC bond formation has been one of the longstanding central topics in synthetic organic chemistry because it is the indispensable methodology for the construction of organic skeletons. In general, an overall redox‐neutral process using a carbon electrophile and a carbon nucleophile is employed owing to preferable polarity of two coupling fragments (Scheme 1.1a). On the other hand, the CC bond‐forming reaction with two different nucleophiles in the presence of suitable chemical oxidants (chemical oxidative CC bond formation) can provide a good alternative to the above overall redox‐neutral process particularly when the corresponding carbon electrophile is difficult to prepare (Scheme 1.1b). Moreover, the ultimate direct CC bond‐forming reaction of two simple CH fragments without any stoichiometric preactivations (e.g. halogenation and metalation) is also theoretically possible. Additionally, the oxidative strategy often enables otherwise challenging CC bond formations with uniquely high chemo‐, regio‐, and stereoselectivity. Such complementary features have prompted synthetic chemists to develop numerous strategies for the oxidative CC bond formation. In this chapter, the recently developed oxidative CC bond formations are categorized according to the carbon hybridization state of the coupling fragments, and their scope, limitations, and mechanisms are briefly summarized.
1.2 Oxidative Aryl–Alkenyl Bond Formation
Since the aryl–alkenyl π‐conjugation frequently occurs in many pharmaceuticals, biologically active compounds, and functional materials, the aromatic Csp2–alkenyl Csp2 bond formation has been widely explored by many synthetic chemists. The most famous and standard approach is the Mizoroki–Heck reaction with aryl halides and alkenes, in conjunction with a suitable palladium catalyst and base [1, 2]. This reaction is the overall redox‐neutral process containing oxidative addition and reductive elimination in the catalytic cycle (Scheme 1.2). Although numerous efforts for development of palladium catalysts and their supporting ligands have allowed various aryl halides, including unactivated aryl chlorides, to be adopted, the alkene fragments are still largely limited to electronically activated α,β‐unsaturated carbonyls and styrenes. Moreover, the preparation of the corresponding aryl halides from the parent arenes (stoichiometric halogenation) is an additional drawback to be addressed. The chemical oxidative coupling approach can be a good solution to the above problems inherent in the classical Mizoroki–Heck reaction. In this section, the oxidative Mizoroki–Heck reaction with arylmetal reagents as aromatic Csp2 fragments and direct aromatic Csp2–alkenyl Csp2 coupling (Fujiwara–Moritani reaction) are mainly presented.
Scheme 1.1 Overall redox‐neutral CC bond formation (a) vs. oxidative CC bond formation (b).
Scheme 1.2 General mechanism of palladium‐catalyzed overall redox‐neutral Mizoroki–Heck reaction of aryl halides with alkenes.
1.2.1 Oxidative Mizoroki–Heck Reaction with Arylmetal Reagents
As mentioned in the above introduction part, the redox‐neutral Mizoroki–Heck reaction still suffers from the relatively narrow scope of alkenes. The oxidative Mizoroki–Heck reaction can address the problem probably because of the formation of more reactive, coordinately unsaturated arylpalladium species through transmetalation between PdX2 and arylmetal reagents rather than the oxidative addition of aryl halides (Scheme 1.3).
In 2008, White and coworkers reported the Pd(OAc)2/bis(sulfoxide) catalyst for the oxidative Mizoroki–Heck reaction with arylboronic acids [3]. In the presence of a benzoquinone (BQ) terminal oxidant, unactivated aliphatic terminal alkenes undergo the Mizoroki–Heck‐type arylation (Scheme 1.4). Milder reaction conditions are compatible with somewhat labile point chirality derived from α‐amino acids as well as functional groups such as a free carboxylic acid. The regioselectivity (internal/terminal) is also well controlled in most cases, but the olefinic position of product (styrenyl/allylic) is highly dependent on the substrate structure and its control still remains a challenging task. A related Pd(IiPr)(OTs)2 catalysis was reported by Sigman and Werner in 2010 (Scheme 1.5): the beneficial point is the use of molecular oxygen as an terminal oxidant, where Cu(OTf)2 is added as a co‐oxidant [4]. Also in this case, the reaction proceeds without erosion‐of‐point chirality. Particularly notable is the high styrenyl/allylic selectivity as well as internal/terminal selectivity in almost all cases.
Scheme 1.3 General mechanism of palladium‐catalyzed oxidative Mizoroki–Heck reaction of arylmetal reagents with alkenes.
Scheme 1.4 Pd(OAc)2/bis(sulfoxide)‐catalyzed oxidative Mizoroki–Heck reaction of unactivated terminal alkenes. BQ = benzoquinone.
While not aryl–alkenyl bond formation, the group of Sigman subsequently developed the enantioselective oxidative Mizoroki–Heck reaction of internal alkenyl alcohols by using the chiral pyridine‐oxazoline hybrid ligand, PyrOx (Scheme 1.6) [5]. The key to success is the redox‐relay process: the alkene is migrated toward the alcohol via an iterative β‐H elimination and insertion, and finally converted to the carbonyl functionality by the formal oxidation event. As a result, the regioselective and enantioselective remote arylation of carbonyl compound is possible. This strategy is also applicable to alkenyl aldehydes and enelactams to deliver the remotely arylated enantioenriched α,β‐unsaturated aldehydes and α,β‐unsaturated δ‐lactams, respectively (Scheme 1.7) [6].
Scheme 1.5 Pd(IiPr)(OTs)‐catalyzed oxidative Mizoroki–Heck reaction of unactivated terminal alkenes. Ts = p‐toluenesulfonyl, Tf = trifluoromethanesulfonyl.
Scheme 1.6 Palladium‐catalyzed enantioselective redox‐relay oxidative Mizoroki–Heck reaction of internal alkenyl alcohols and its redox‐relay mechanism.
Source: Modified from Mei et al. [5].
1.2.2 Direct Oxidative Mizoroki–Heck Reaction with Arene C–Hs (Fujiwara–Moritani Reaction)
One of the biggest drawbacks in the above Mizoroki–Heck reaction with aryl halides or aryl boronic acids is their tedious preparation from the parent simple arenes. In 1969, Fujiwara et al. reported seminal work on the palladium‐catalyzed coupling reaction of simple arenes and alkenes, in the presence of Cu(OAc)2 or AgOAc terminal oxidant, to form the corresponding alkenylarenes directly (Scheme 1.8) [7]. This protocol received significant attention from the viewpoint of organic synthesis because the arene C–H and alkene C–H are directly cross‐coupled without any preactivation steps of both starting substrates. Since then, such a transition‐metal‐promoted “C–H activation” strategy has greatly and rapidly progressed by efforts of many research groups, and the Fujiwara–Moritani reaction is now a powerful synthetic tool for the construction of aryl–alkenyl π‐conjugation. However, the disadvantage of early studies on the Fujiwara–Moritani reaction is the inevitable use of excess arene substrates (in many cases solvent amount).
Scheme 1.7 Palladium‐catalyzed enantioselective redox‐relay oxidative Mizoroki–Heck reaction of alkenyl aldehydes and enelactams.
Source: Modified from Zhang et al. [6a], Yuan and Sigman [6b].
Scheme 1.8 General reaction scheme and mechanism of palladium‐catalyzed Fujiwara–Moritani reaction.
Source: Modified from Fujiwara et al. [7a], Jia et al. [7b].
In this context, Yu and coworkers reported the Fujiwara–Moritani reaction with the simple arene as the limiting reagent (1.0 equiv) under Rh(II)/PCy3/Cu(TFA)2/V2O5 oxidative catalysis (Scheme 1.9) [8]. Although the exact role of PCy3 ligand as well as copper and vanadium combined oxidation system still remains to be elucidated, the reaction proceeds smoothly even in the presence of 1 equiv of simple arenes. More recently, the same research group developed the well‐defined and robust Pd(OAc)2/hydroxypyridine catalyst for the reaction with much broader simple arenes, including benzene derivatives, heteroaromatics, and even more challenging complex drug‐like molecules (Scheme 1.10) [9]. Also in this case, the arene substrate works well even at 1 equiv loading. The well‐designed hydroxypyridine ligand is key to success, and its pivotal role in the C–H activation step of otherwise unreactive simple arene is also uncovered by computational studies with density functional theory (DFT) calculation. Although the alkene coupling partners are still limited to electronically activated acrylates and styrenes, the above work successfully overcomes the big issue in the conventional Fujiwara–Moritani reaction.
Scheme 1.9 Rhodium(II)‐catalyzed Fujiwara–Moritani reaction of simple arenes as limiting reagents. DCE = 1,2‐dichloroethane.
Source: Modified from Vora et al. [8].
Scheme 1.10 Palladium/hydroxypyridine‐catalyzed Fujiwara–Moritani reaction of simple arenes as limiting reagents and proposed transition state based on DFT calculation. HFIP = 1,1,1,3,3,3‐hexafluoroisopropyl alcohol.
Source: Modified from Wang et al. [9].
Additional inherent problem of the Fujiwara–Moritani reaction is the regioselectivity: for example, when the mono‐substituted arene is employed, there are three possible reaction sites, namely ortho, meta, and para C–Hs, and its control is also of great importance in chemical synthesis. A good solution of such a regioselective issue is the introduction of coordinating functional group (directing group): a suitable functional group coordinates to the metal center to promote the C–H activation at the proximal ortho position. The formed five‐ or six‐membered metalacycle intermediate undergoes the insertion reaction with the alkene substrate, eventually leading to the ortho‐alkenylated product with high regioselectivity. Since Murai's et al. milestone work on the ruthenium‐catalyzed ortho‐alkylation of ketones[10], numerous research groups joined this field to develop various directing groups containing nitrogen, oxygen, sulfur, phosphorus, and even less polar CC π‐bond [11]. A representative example of indole carboxylic acids is shown in Scheme 1.11. In this case, the carboxyl group works as a unique “traceless” ortho‐directing group: 2‐ and 3‐indole carboxylic acids react with the acrylate with concomitant decarboxylation under palladium catalysis to furnish 3‐ and 2‐alkenylated indoles, regioselectively [12].
Scheme 1.11 Carboxylic‐acid‐directed ortho‐selective Fujiwara–Moritani reaction of indole carboxylic acids with concomitant decarboxylation.
In addition to the palladium salts, Cp*Rh(III) catalysts also show high performance in the directed Fujiwara–Moritani reaction. In 2007, Satoh and coworkers reported the pioneering work on the Cp*Rh(III)‐catalyzed ortho‐selective alkenylation of benzoic acids with acrylates (Scheme 1.12) [13]. The initially formed alkenylated product spontaneously undergoes intramolecular Michael‐type addition of carboxylic acid directing group to form the observed lactone derivative. Additional beneficial point of the Cp*Rh(III) catalysis is the reoxidation system: the most environmentally benign atmospheric molecular oxygen works as a terminal oxidant in the presence of a catalytic amount of internal oxidant, Cu(OAc)2·H2O. Thus, the formed byproduct is only nontoxic water. Since then, more and more oxidative coupling reactions between aromatic compounds and alkenes or alkynes have been explosively developed under the Rh(III)/Cu(II) or related Rh(III)/Ag(I) oxidative catalysis [14].
Scheme 1.12 Cp*Rh(III)‐catalyzed ortho‐selective Fujiwara–Moritani reaction of benzoic acids with acrylates. Cp* = 1,2,3,4,5‐pentamethylcyclopentadienyl.
Source: Modified from Ueura et al. [13].
The directed meta‐ or para‐alkenylation is much more challenging than the ortho‐alkenylation because of formation of kinetically less favored medium‐ and large‐sized metalacycle intermediate. However, some seminal works recently appeared. In 2012, Yu and coworkers elegantly designed the nitrile‐based, U‐shaped template to direct the meta‐selective Fujiwara–Moritani reaction under Pd/Ag catalysis (Scheme 1.13) [15]. Owing to the end‐on coordinating nature of nitrile, the relatively large and unique Pd/Ag bimetallic metalacycle is formed as the key intermediate, which is supported by computational studies in the follow‐up article [16]. This work prompted several researchers to develop the related directing groups for the meta‐C–H alkenylation of various aromatic compounds, but all of them still rely on the nitrile functionality [17]. The same strategy is also effective for the rhodium‐catalyzed meta‐C–H alkenylation (Scheme 1.14) [18].
Scheme 1.13 Palladium/silver‐catalyzed meta‐selective Fujiwara–Moritani reaction assisted by nitrile‐based U‐shaped template and proposed bimetallic transition state in C–H activation. Piv = tert‐butylcarbonyl.
Source: Modified from Leow et al. [15].
In 2015, Maiti and coworkers developed a similar nitrile‐based D‐shaped template for the para‐selective Fujiwara–Moritani reaction (Scheme 1.15) [19]. The biggest feature is the long biphenyl template ligated with flexible Si tether of sp3 hybridization. Additionally, the positive Thorpe–Ingold effect is successfully promoted by two bulky isopropyl groups on Si. In the presence of a Pd(OAc)2 catalyst and amino acid ligand, Ac‐Phe‐OH, a variety of benzene derivatives undergo the alkenylation selectively at the para position beyond their innate electronic biases.
1.3 Oxidative Aryl–Aryl Bond Formation
Due to the ubiquity of biaryl structure in biologically active compounds, natural products, pharmaceutical targets, and organic functional materials, the aromatic Csp2–aromatic Csp2 bond‐forming reaction is always one of the hot research topics in synthetic organic chemistry. The Nobel Prize–winning palladium‐catalyzed overall redox‐neutral cross‐coupling reaction of aryl halides with arylmetal reagents is now the most powerful and reliable approach to the above biaryl linkage (Scheme 1.16, left). On the other hand, the oxidative aryl–aryl bond‐forming reaction can replace the aryl halide electrophiles with the simple and readily accessible arenes (C–H/C–M cross‐coupling; Scheme 1.16, right). Such an oxidative coupling protocol often enables the challenging biaryl coupling under the redox‐neutral conditions. Moreover, an ideal oxidative cross‐coupling of two simple arenes (C–H/C–H cross‐coupling) is potentially possible. In this section, the recent advances in the above two types of oxidative biaryl coupling are demonstrated.
Scheme 1.14 Rhodium‐catalyzed meta‐selective Fujiwara–Moritani reaction assisted by nitrile‐based U‐shaped template.
Source: Modified from Xu et al. [18a], Bera et al. [18b].
Scheme 1.15 Palladium‐catalyzed para‐selective Fujiwara–Moritani reaction assisted by nitrile‐based D‐shaped template. Ac‐Phe‐OH = N‐acetylphenylalanine.
Source: Modified from Bag et al. [19a], Patra et al. [19b].
Scheme 1.16 General mechanisms of overall redox‐neutral biaryl cross‐coupling of aryl halide and arylmetal (left) and oxidative biaryl cross‐coupling of simple arene and arylmetal or another simple arene (right).
1.3.1 Oxidative C–H/C–M Biaryl Cross‐Coupling
Electron‐rich heterocycles such as indole, thiazole, and pyrrole relatively easily participate in the oxidative biaryl cross‐coupling reaction with arylmetals (Scheme 1.17). In the case of indole, the simple Pd(OAc)2‐catalyzed C–H arylation with phenylboronic acid often proceeds even at room temperature by using the molecular oxygen as the sole oxidant [20]. Owing to its experimental simplicity, the reaction is also easily scaled up to a gram quantity. The thiazole is also arylated in the presence of a Pd(OAc)2/1,10‐phenanthroline (phen) catalyst and 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) oxidant [21]. The additional unique feature is the otherwise challenging C4 selectivity. Although generally less reactive, the abundant first‐row transition metals also promote similar reactions. For example, Cu(TFA)2 mediates the multiple oxidative arylation of pyrrole with excess phenylboronic acid to form the tetraphenylpyrrole in one shot [22].
The 1,3‐azoles have relatively acidic C–Hs at the C2 position, and thus they are more reactive under somewhat basic conditions. The oxazole and imidazole are directly arylated selectively at the C2 position under cost‐effective nickel catalysis (Scheme 1.18) [23]. Notably, in the latter case, the less reactive arylsilane also works well as the arylation reagent.
The benzene derivatives are less reactive than heteroarenes mentioned above, and the suitable coordinating functional groups, namely directing groups, are generally essential for obtaining satisfactory reactivity as well as control of regioselectivity (Scheme 1.19). Similar to the Fujiwara–Moritani reaction (Schemes 1.11 and 1.12), the carboxyl group is the effective ortho‐directing group under oxidative Pd(II)/BQ catalysis to deliver the corresponding arylated product in a good yield [24]. With the assistance of well‐designed N,N‐bidentately coordinating group, the abundant copper salt also catalyzes the C–H arylation with the arylboronate in the presence of Ag2O oxidant [25].
Scheme 1.17 Oxidative C–H/C–M biaryl coupling of electron‐rich indole, thiazole, and pyrrole.
Scheme 1.18 Nickel‐catalyzed oxidative C–H/C–M biaryl coupling of relatively acidic C2 C–Hs of 1,3‐azoles. bpy = 2,2′‐bipyridyl.
Source: Modified from Hachiya et al. [23].
Scheme 1.19 Oxidative C–H/C–M biaryl coupling of benzene derivatives with assistance of directing groups.
Exceptionally, the highly fused benzene derivatives show a remarkably high reactivity under the oxidative C–H arylation conditions because of their lower aromaticity, i.e. alkene‐like reactivity (Scheme 1.20). In 2011, Itami and coworkers reported the Pd(II)/o‐chloranil oxidative catalyst for the C–H arylation of pyrene derivatives with arylboroxines [26]. The reaction is apparently unique to the higher‐fused aromatics but of great interest in the bottom‐up synthesis of π‐extended polyaromatic hydrocarbons (PAHs), which have received tremendous attention in the field of material science. Actually, application to the rapid and concise synthesis of extended PAHs was demonstrated by the C–H arylation/Scholl reaction sequence. Subsequently, the same catalyst system was successfully applied to the K‐region‐selective one‐shot π‐extension with the dibenzosiloles [27]. The o‐chloranil is the key of catalysis, and its multitask nature as the ligand, oxidant, and base was recently uncovered by computational studies with DFT calculation.
Scheme 1.20 Pd/o‐chloranil‐catalyzed oxidative C–H/C–M biaryl coupling of higher fused benzene derivatives. DCM = dichloromethane.
As mentioned in Schemes 1.17, 1.18, 1.19, 1.20, the air‐stable and easy‐to‐handle arylboronic acids and arylsilanes are frequently employed as the arylmetals in the oxidative C–H/C–M biaryl coupling reaction. Although still limited in scope, more readily available benzoic acids can also couple with some arene C–Hs, via decarboxylation, to afford the corresponding biaryls under appropriate oxidative conditions (Scheme 1.21). The decarboxylative C–H arylation of indole and oxazole derivatives efficiently occurs in the presence of Pd(II)/Ag(I) or Cu(II) oxidative catalysts [28]. The copper salt alone also mediates a similar reaction of benzamide substrate that bears the suitable 8‐aminoquinoline‐based N,N‐bidentate coordination [29].
1.3.2 Oxidative C–H/C–H Biaryl Cross‐Coupling
The direct oxidative coupling of two different arenes via dual CH bond cleavage is the most attractive and ideal approach to the biaryl structure from the
