Edited by rising stars in the scientific community, the text focuses solely on visible light photocatalysis in the context of organic chemistry. This primarily entails photoinduced electron transfer and energy transfer chemistry sensitized by polypyridyl complexes, yet also includes the use of organic dyes and heterogeneous catalysts.
A valuable resource to the synthetic organic community, polymer and medicinal chemists, as well as industry professionals.
Table of Contents
1 An Overview of the Physical and Photophysical Properties of [Ru(bpy)3]2+ 1
DanielaM. Arias-Rotondo and James K. McCusker
1.1 Introduction 1
1.2 [Ru(bpy)3]2+: Optical and Electrochemical Properties 4
1.2.1 Optical Properties 4
1.2.2 Electrochemical Properties 6
1.3 Excited State Kinetics 8
1.3.1 Steady-State Emission 8
1.3.2 Time-Resolved Emission 10
1.4 Excited-State Reactivity of [Ru(bpy)3]2+ 11
1.5 Energy Transfer: Förster and Dexter Mechanisms 12
1.6 Electron Transfer 14
1.7 Probing the Mechanism, Stage I: Stern–Volmer Quenching Studies 14
1.8 Probing the Mechanism, Stage II: Electron Versus Energy Transfer 16
1.9 Designing Photocatalysts: [Ru(bpy)3]2+ as a Starting Point 20
1.10 Conclusion 22
References 23
2 Visible-Light-Mediated Free Radical Synthesis 25
Louis Fensterbank, Jean-Philippe Goddard, and Cyril Ollivier
2.1 Introduction 25
2.2 Basics of the Photocatalytic Cycle 26
2.3 Generation of Radicals 27
2.3.1 Formation of C-Centered Radicals 27
2.3.1.1 Dehalogenation (I, Br, Cl) 27
2.3.1.2 Other C-Heteroatom Cleavage 29
2.3.1.3 C - C Bond Cleavage 29
2.3.2 Formation of N-Centered Radicals 30
2.4 C - X Bond Formation 30
2.4.1 C - O Bond 30
2.4.2 C - N Bond 32
2.4.3 C - S and C - Se Bonds 33
2.4.4 C - Br Bond 34
2.4.5 C - F Bond 34
2.4.6 C - B Bond 35
2.5 C - C Bond Formation 35
2.5.1 Formation and Reactivity of Aryl Radicals 35
2.5.2 Formation and Reactivity of Trifluoromethyl and Related Radicals 40
2.5.2.1 Photocatalyzed Reduction of Perfluorohalogen Derivatives 40
2.5.2.2 Photocatalyzed Reduction of Perfluoroalkyl-Substituted Onium Salts 42
2.5.2.3 Photocatalyzed Formation of Perfluoroalkyl Radicals from Sulfonyl and Sulfinyl Derivatives 43
2.5.3 Formation and Reactivity of Alkyl and Related Radicals 45
2.5.3.1 C - C Bond FormationThrough Photocatalyzed Reduction of Halogen Derivatives and Analogs 45
2.5.3.2 C - C Bond FormationThrough Photocatalyzed Oxidation of Electron-Rich Functional Group 47
2.5.3.3 C - C Bond FormationThrough Photocatalyzed Oxidation of Amino Group 48
2.6 Radical Cascade Applications 49
2.6.1 Intramolecular Polycyclization Processes 49
2.6.2 Sequential Inter- and Intramolecular Processes 51
2.6.3 Sequential Radical and Polar Processes 56
References 59
3 AtomTransfer Radical Addition using Photoredox Catalysis 73
Theresa M.Williams and Corey R. J. Stephenson
3.1 Introduction 73
3.2 Transition Metal-Catalyzed ATRA 77
3.2.1 Ruthenium- and Iridium-Based ATRA 77
3.2.1.1 Mechanistic Investigations 77
3.2.1.2 Ruthenium- and Iridium-Based ATRA 80
3.2.2 Copper-Mediated ATRA 81
3.2.2.1 Trifluoromethylation 82
3.3 Other Photocatalysts for ATRA Transformations 84
3.3.1 p-Anisaldehyde 84
3.4 Semiconductor 86
3.5 Atom Transfer Radical Cyclization (ATRC) 87
3.6 Atom Transfer Radical Polymerization (ATRP) 89
3.7 Conclusion 90
References 90
4 Visible Light Mediated ;;-Amino C - H Functionalization Reactions 93
You-Quan Zou andWen-Jing Xiao
4.1 Introduction 93
4.2 Visible Light Mediated α-Amino C - H Functionalization Via Iminium Ions 95
4.2.1 Aza-Henry Reaction 95
4.2.2 Mannich Reaction 100
4.2.3 Strecker Reaction 104
4.2.4 Friedel–Crafts Reaction 105
4.2.5 Alkynylation Reaction 108
4.2.6 Phosphonation Reaction 109
4.2.7 Addition of 1,3-Dicarbonyls 109
4.2.8 Formation of C - N and C - O Bonds 110
4.2.9 Miscellaneous 112
4.3 Visible Light Mediated α-Amino C - H Functionalization Via α-Amino Radicals 116
4.3.1 Addition to Electron-Deficient Aromatics 116
4.3.2 Addition to Electron-Deficient Alkenes 116
4.3.3 Miscellaneous 120
4.4 Conclusions and Perspectives 121
References 122
5 Visible Light Mediated Cycloaddition Reactions 129
Scott Morris, Theresa Nguyen, and Nan Zheng
5.1 Introduction 129
5.2 [2+2] Cycloadditions: Formation of Four-Membered Rings 130
5.2.1 Introduction to [2+2] Cycloadditions 130
5.2.2 Utilization of the Reductive Quenching Cycle 130
5.2.3 Utilization of the Oxidative Quenching Cycle 135
5.2.4 Utilization of Energy Transfer 139
5.2.5 [2+2] Conclusion 142
5.3 [3+2] Cycloadditions: Formation of Five-Membered Rings 143
5.3.1 Introduction to [3+2] Cycloadditions 143
5.3.2 [3+2] Cycloaddition of Cyclopropylamines 143
5.3.3 1,3-Dipolar Cycloaddition of Azomethine Ylides 145
5.3.4 [3+2] Cycloaddition of Aryl Cyclopropyl Ketones 146
5.3.5 [3+2] Cycloaddition via ATRA/ATRC 146
5.3.6 [3+2] Conclusion 148
5.4 [4+2] Cycloadditions: Formation of Six-Membered Rings 149
5.4.1 Introduction to [4+2] Cycloadditions 149
5.4.2 [4+2] Cycloadditions Using Radical Anions 149
5.4.3 [4+2] Cycloadditions Using Radical Cations 151
5.4.4 [4+2] Conclusion 154
5.5 Conclusion 155
References 156
6 Metal-Free Photo(redox) Catalysis 159
Kirsten Zeitler
6.1 Introduction 159
6.1.1 Background 162
6.1.2 Classes of Organic Photocatalysts 162
6.2 Applications of Organic Photocatalysts 166
6.2.1 Energy Transfer Reactions 166
6.2.2 Reductive Quenching of the Catalyst 171
6.2.2.1 Cyanoarenes 171
6.2.2.2 Quinones 172
6.2.2.3 Cationic Dyes: Pyrylium, Quinolinium, and Acridinium Scaffolds 173
6.2.2.4 Xanthene Dyes and Further Aromatic Scaffolds 188
6.2.3 Oxidative Quenching of the Catalyst 203
6.2.4 New Developments 214
6.2.4.1 Upconversion 215
6.2.4.2 Consecutive Photoelectron Transfer 215
6.2.4.3 Multicatalysis 216
6.3 Conclusion and Outlook 224
References 224
7 Visible Light and Copper Complexes: A Promising Match in Photoredox Catalysis 233
Suva Paria and Oliver Reiser
7.1 Introduction 233
7.2 Photophysical Properties of Copper Catalysts 234
7.3 Application of Copper Based Photocatalysts in Organic Synthesis 237
7.4 Outlook 247
Acknowledgment 248
References 248
8 Arene Functionalization by Visible Light Photoredox Catalysis 253
Durga Hari Prasad, Thea Hering, and Burkhard König
8.1 Introduction 253
8.1.1 Aryl Diazonium Salts 253
8.1.2 Diaryl Iodonium Salts 268
8.1.3 Triaryl Sulfonium Salts 272
8.1.4 Aryl Sulfonyl Chlorides 273
8.2 Applications of Aryl Diazonium Salts 274
8.3 Photoinduced Ullmann C - N Coupling 276
8.4 Conclusion 278
References 278
9 Visible-Light Photocatalysis in the Synthesis of Natural Products 283
Gregory L. Lackner, KyleW. Quasdorf, and Larry E. Overman
References 295
10 Dual Photoredox Catalysis: TheMerger of Photoredox Catalysis with Other Catalytic Activation Modes 299
Christopher K. Prier and DavidW. C. MacMillan
10.1 Introduction 299
10.2 Merger of Photoredox Catalysis with Organocatalysis 300
10.3 Merger of Photoredox Catalysis with Acid Catalysis 314
10.3.1 Photoredox Catalysis and Brønsted Acid Catalysis 314
10.3.2 Photoredox Catalysis and Lewis Acid Catalysis 318
10.4 Merger of Photoredox Catalysis with Transition Metal Catalysis 320
10.5 Conclusions 328
References 328
11 Enantioselective Photocatalysis 335
Susannah C. Coote and Thorsten Bach
11.1 Introduction 335
11.2 The Twentieth Century: PioneeringWork 336
11.3 The Twenty-First Century: Contemporary Developments 341
11.3.1 Large-Molecule Chiral Hosts 341
11.3.2 Small-Molecule Chiral Photosensitizers 343
11.3.3 Lewis Acid-Mediated Photoreactions 353
11.4 Conclusions and Outlook 357
References 358
12 Photomediated Controlled Polymerizations 363
Nicolas J. Treat, Brett P. Fors, and Craig J. Hawker
12.1 Catalyst Activation by Light 365
12.1.1 Cu-Catalyzed Photoregulated Atom Transfer Radical Polymerizations (photoATRP) 365
12.1.2 Photomediated ATRP with Non-Copper-Based Catalyst Systems 368
12.1.3 Iodine-Mediated Photopolymerizations 371
12.1.4 Metal-Free Photomediated Ring-Opening Metathesis Polymerization 375
12.1.5 Photoregulated Reversible-Addition Fragmentation Chain Transfer Polymerizations (photoRAFT) 376
12.2 Chain-End Activation by Light 383
12.3 Conclusions 384
References 385
13 Accelerating Visible-Light Photoredox Catalysis in Continuous-Flow Reactors 389
Natan J.W. Straathof and Timothy Noël
13.1 Introduction 389
13.2 Homogeneous Photocatalysis in Single-Phase Flow 392
13.3 Gas–liquid Photocatalysis in Flow 401
13.4 Heterogeneous Photocatalysis in Flow 408
13.5 Conclusions 410
Conflict of Interest 410
References 410
14 The Application of Visible-Light-Mediated Reactions to the Synthesis of Pharmaceutical Compounds 415
James. J. Douglas
14.1 Introduction 415
14.2 Asymmetric Benzylation 415
14.3 Amide Bond Formation 416
14.4 C - H Azidation 417
14.5 Visible-Light-Mediated Benzothiophene Synthesis 418
14.6 α-Amino Radical Functionalization 419
14.7 Visible-Light-Mediated Radical Smiles Rearrangement 422
14.8 Photoredox and Nickel Dual Catalysis 423
14.9 The Scale-Up of Visible-Light-Mediated Reactions Via Continuous
Processing 426
References 428
Index 431
