Preface ...................................................... xiii
Acknowledgements ............................................... xv
Contributors ................................................. xvii
1. General Aspects of Organosuperbases .......................... 1
Tsutomu Ishikawa
References ................................................... 6
2. Physico-Chemical Properties of Organosuperbases .............. 9
Davor Margetic
2.1 Introduction ............................................ 9
2.2 Proton Sponges ......................................... 10
2.2.1 'Classical' Proton Sponges ...................... 10
2.2.2 Proton Sponges with Other Aromatic Backbones .... 12
2.2.3 Polycyclic Proton Sponges ....................... 14
2.3 Amidines ............................................... 20
2.4 Guanidines ............................................. 24
2.5 Phosphazenes ........................................... 31
2.6 Guanidinophosphazenes .................................. 35
2.7 Other Phosphorus Containing Superbases: Verkade's
Proazaphosphatranes .................................... 37
2.8 Theoretical Methods .................................... 41
2.9 Concluding Remarks ..................................... 41
References ............................................. 42
3. Amidines in Organic Synthesis ............................... 49
Tsutomu Ishikawa and Takuya Kumamoto
3.1 Introduction ........................................... 49
3.2 Preparation of Amidines ................................ 52
3.2.1 Alkylation of Amidines .......................... 52
3.2.2 Condensation of 1,2-Diamine ..................... 53
3.2.3 Coupling of Imines (Isoamarine Synthesis) ....... 53
3.2.4 Modification of Amide Derivatives ............... 54
3.2.5 Multi-Component Reaction ........................ 59
3.2.6 Oxidative Amidination ........................... 62
3.2.7 Oxidative Cyclization to Bisamidine ............. 63
3.2.8 Ring Opening of Aziridine ....................... 63
3.3 Application of Amidines to Organic Synthesis ........... 65
3.3.1 Acetoxybromination .............................. 65
3.3.2 Aldol-Like Reaction ............................. 66
3.3.3 Azidation ....................................... 67
3.3.4 Aziridination ................................... 68
3.3.5 Baylis-Hillman Reaction ......................... 68
3.3.6 Cycloaddition ................................... 68
3.3.7 Dehydrohalogenation ............................. 70
3.3.8 Deprotection .................................... 70
3.3.9 Deprotonation ................................... 71
3.3.10 Displacement Reaction ........................... 72
3.3.11 Horner-Wadsworth-Emmons Reaction ................ 72
3.3.12 Intramolecular Cyclization ...................... 72
3.3.13 Isomerization ................................... 72
3.3.14 Metal-Mediated Reaction ......................... 74
3.3.15 Michael Reaction ................................ 77
3.3.16 Nef Reaction .................................... 78
3.3.17 Nucleophilic Epoxidation ........................ 79
3.3.18 Oxidation ....................................... 80
3.3.19 Pudovik-phospha-Brook Rearrangement ............. 80
3.3.20 [1,4]-Silyl Transfer ............................ 80
3.3.21 Tandem Reaction ................................. 81
3.4 Amidinium Salts: Design and Synthesis .................. 82
3.4.1 Catalyst ........................................ 82
3.4.2 Molecular Recognition ........................... 82
3.4.3 Reagent Source .................................. 85
3.5 Concluding Remarks ..................................... 86
References ............................................. 86
4. Guanidines in Organic Synthesis ............................. 93
Tsutomu Ishikawa
4.1 Introduction ........................................... 93
4.2 Preparation of Chiral Guanidines ....................... 94
4.2.1 Polysubstituted Acyclic and Monocyclic
Guanidines ...................................... 95
4.2.2 Monosubstituted Guanidines (Guanidinylation) .... 95
4.2.3 Bicyclic Guanidines ............................. 97
4.2.4 Preparation Based on DMC Chemistry .............. 98
4.3 Guanidines as Synthetic Tools .......................... 99
4.3.1 Addition ........................................ 99
4.3.2 Substitution ................................... 112
4.3.3 Others ......................................... 117
4.4 Guanidinium Salt ...................................... 125
4.4.1 Guanidinium Ylide .............................. 125
4.4.2 Ionic Liquid ................................... 128
4.4.3 Tetramethylguanidinium Azide (TMGA) ............ 131
4.5 Concluding Remarks .................................... 136
References ................................................. 136
5. Phosphazene: Preparation, Reaction and Catalytic Role ...... 145
Yoshinori Kondo
5.1 Introduction .......................................... 145
5.2 Deprotonative Transformations Using Stoichiometric
Phosphazenes .......................................... 150
5.2.1 Use of PI Base ................................. 151
5.2.2 Use of P2 Base ................................. 156
5.2.3 Use of P4 Base ................................. 159
5.2.4 Use of P5 Base ................................. 164
5.3 Transformation Using Phosphazene Catalyst ............. 164
5.3.1 Addition of Nucleophiles to Alkyne ............. 164
5.3.2 Catalytic Activation of Silylated
Nucleophiles ................................... 165
5.4 Proazaphosphatrane Base (Verkade's Base) .............. 176
5.4.1 Properties of Proazaphosphatrane ............... 176
5.4.2 Synthesis Using Proazaphosphatrane ............. 176
5.5 Concluding Remarks ............................... 181
References ................................................. 181
6. Polymer-Supported Organosuperbases ......................... 187
Hiyoshizo Kotsuki
6.1 Introduction .......................................... 187
6.2 Acylation Reactions ................................... 188
6.3 Alkylation Reactions .................................. 190
6.4 Heterocyclization ..................................... 198
6.5 Miscellaneous ......................................... 200
6.6 Concluding Remarks .................................... 205
References ................................................. 205
7. Application of Organosuperbases to Total Synthesis ......... 211
Kazuo Nagasawa
7.1 Introduction .......................................... 211
7.2 Carbon-Carbon Bond Forming Reactions .................. 211
7.2.1 Aldol Reaction ................................. 211
7.2.2 Michael Reaction ............................... 215
7.2.3 Pericyclic Reaction ............................ 217
7.2.4 Wittig Reaction ................................ 220
7.3 Deprotection .......................................... 225
7.4 Elimination ........................................... 225
7.5 Ether Synthesis ....................................... 230
7.6 Heteroatom Conjugate Addition ......................... 233
7.7 Isomerization ......................................... 237
7.8 Concluding Remarks .................................... 247
References ................................................. 247
8. Related Organocatalysts (1): A Proton Sponge ............... 251
Kazuo Nagasawa
8.1 Introduction .......................................... 251
8.2 Alkylation and Hetero Michael Reaction ................ 252
8.2.1 Amine Synthesis by N~Alkylation ................ 252
8.2.2 Ether Synthesis by O-Alkylation ................ 252
8.3 Amide Formation ....................................... 256
8.4 Carbon-Carbon Bond Forming Reaction ................... 259
8.4.1 Alkylation and Nitro Aldol Reaction ............ 259
8.4.2 Pericyclic Reaction ............................ 261
8.5 Palladium Catalyzed Reaction .......................... 264
8.6 Concluding Remarks .................................... 268
References ................................................. 268
9. Related Organocatalysts (2): Urea Derivatives .............. 273
Waka Nakanishi
9.1 Introduction .......................................... 273
9.2 Bisphenol as an Organoacid Catalyst ................... 274
9.2.1 Role of Phenol as Hydrogen Donor ............... 274
9.2.2 Bisphenol Catalysed Reaction ................... 276
9.3 Urea and Thiourea as Achiral Catalysts ................ 277
9.3.1 Role of Urea and Thiourea as Hydrogen Donors ... 277
9.3.2 Urea and Thiourea Catalysed Reactions .......... 278
9.4 Urea and Thiourea as Chiral Catalysts ................. 282
9.4.1 Monothiourea Catalysts ......................... 284
9.4.2 Bisthiourea Catalysts .......................... 289
9.4.3 Urea-Sulfinimide Hybrid Catalyst ............... 290
9.5 Concluding Remarks .................................... 291
References ............................................ 292
10. Amidines and Guanidines in Natural Products and
Medicines ................................................. 295
Takuya Kumamoto
10.1 Introduction ......................................... 295
10.2 Natural Amidine Derivatives .......................... 295
10.2.1 Natural Amidines from Microorganisms and
Fungi ......................................... 296
10.2.2 Natural Amidines from Marine Invertebrates .... 298
10.2.3 Natural Amidines from Higher Plants ........... 299
10.3 Natural Guanidine Derivatives ........................ 299
10.3.1 Natural Guanidines from Microorganisms ........ 300
10.3.2 Natural Guanidines from Marine
Invertebrates ................................. 301
10.3.3 Natural Guanidines from Higher Plant .......... 302
10.4 Medicinal Amidine and Guanidine Derivatives .......... 303
10.4.1 Biguanides .................................... 305
10.4.2 Cimetidine .................................... 305
10.4.3 Imipenem ...................................... 306
10.4.4 NOS Inhibitors ................................ 307
10.4.5 Pentamidine ................................... 307
References ................................................ 308
11. Perspectives .............................................. 315
Tsutomu Ishikawa and Davor Margetic
References ................................................ 319
Index ......................................................... 321
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