Reaction Mechanisms in Organic Synthesis

by Parashar, Rakesh Kumar

• ISBN13: 9781405190893
• ISBN10: 1405190892
• Edition: 1st
• Format: Paperback
• Copyright: 2008-12-22
• Publisher: Wiley-Blackwell

Summary

The jump from an understanding of organic chemistry at undergraduate level to that required at postgraduate level or in industry can be difficult. Many advanced textbooks contain hundreds of examples of various reaction mechanisms, in a level of detail which obscures the essential framework underling and uniting those reactions. Understanding this underlying order is essential in any advanced study or application of organic chemistry. By discussing organic reaction mechanism in the context of organic synthesis, this book provides a highly practical, structured framework from which to build a good understanding of the essential underlying principles of organic reactions. The focus on synthetically useful reactions ensures the contents are specifically relevant to postgraduate students and industrial organic chemists.

Author Biography

Rakesh Kumar Parashar is a Reader at the Chemistry Deparment, Kirori Mal College, University of Delhi, India

Table of Contents

Foreword	p. xi
Preface	p. xiii
About the Author	p. xv
Acknowledgements	p. xv
Abbreviations	p. xvii
Synthetic Strategies	p. 1
An introduction to organic synthesis	p. 1
Retrosynthetic analysis (disconnection approach)	p. 2
Unpolung strategy	p. 6
Atom economy	p. 8
Selectivity	p. 10
Chemoselectivity	p. 11
Regioselectivity	p. 12
Stereoselectivity	p. 13
Asymmetric synthesis or chiral synthesis	p. 16
Protecting groups	p. 26
Common hydroxy protecting groups	p. 27
Common diols protecting groups	p. 36
Common amine protecting groups	p. 38
Common carbonyl protecting groups	p. 42
Common carboxylic acid protecting groups	p. 45
Common arenesulfonic acid protecting groups	p. 47
Common alkyne protecting groups	p. 48
References	p. 48
Reactive Intermediates	p. 51
Carbocations	p. 51
Structure and stability of carbocations	p. 51
Generation of carbocations	p. 53
Reactions of carbocations	p. 54
Non-classical carbocations	p. 60
Carbanions	p. 63
Structure and stability of carbanions	p. 63
Generation of carbanions	p. 65
Reactions of carbanions	p. 65
Free radicals	p. 70
Structure and stability of free radicals	p. 71
Generation of free radicals	p. 72
Radical ions	p. 76
Reactions of radicals	p. 77
Carbenes	p. 90
Structure and stability of carbenes	p. 92
Generation of carbenes	p. 93
Reactions of carbenes	p. 95
Nitrenes	p. 101
Structure and stability of nitrenes	p. 101
Generation of nitrenes	p. 101
Reactions of nitrenes	p. 102
Benzynes	p. 105
Generation of benzynes	p. 105
Reactions of benzynes	p. 106
References	p. 109
Stabilized Carbanions, Enamines and Ylides	p. 112
Stabilized carbanions	p. 112
Reaction of stabilized carbanions (enolates) with alkyl halides (enolate alkylation)	p. 114
Reaction of stabilized carbanions with carbonly compounds	p. 118
Conjugate addition of enolate to ¿, ß-unsturated carbonyl compounds	p. 125
Reaction of enolates with iminium ions or imines	p. 127
Enamines	p. 130
Ylides	p. 134
Formation of ylides	p. 135
Reactions of ylides	p. 137
Asymmetric ylide reactions	p. 142
References	p. 146
Carbon-Carbon Double Bond Forming Reactions	p. 148
Introduction	p. 148
Elimination reactions	p. 148
ß-Eliminations	p. 148
Unimolecular syn-eliminations	p. 153
Reactions from epoxides, thionocarbonates and episulfides	p. 156
Alkenation (alkylidenation) of carbonyl compounds	p. 157
Wittig reactions	p. 158
Julia alkenation and modified Julia alkenation (Julia-Kocienski alkenation)	p. 166
Peterson reaction	p. 172
Use of titanium-based reagents	p. 174
Use of Zinc (Zn) and Zirconium (Zr) reagents for the alkenation of ketones and aldehydes	p. 182
Bamford-Stevens reaction and Shapiro reaction	p. 184
Barton-Kellogg reaction	p. 185
Catalytic aldehyde and ketone alkenation	p. 187
Reduction of alkynes	p. 188
References	p. 189
Transition Metal-Mediated Carbon-Carbon Bond Forming Reactions	p. 191
Carbon-carbon bond forming reactions catalyzed by transition metals	p. 193
Heck reaction	p. 193
Allylic substitutions	p. 198
Cu-and Ni-catalyzed couplings	p. 201
Transition metal-catalyzed coupling of organometallic reagents with organic halides and related electrophiles	p. 203
Coupling of Grignard reagents	p. 205
Coupling of organostannanes	p. 208
Coupling of organoboranes	p. 211
Coupling of organosilanes	p. 213
Coupling of organocopper reagents	p. 215
Coupling of organozinc compounds	p. 216
References	p. 222
Reduction	p. 224
Reduction of carbon-carbon double bond	p. 224
Catalytic hydrogenation	p. 224
Hydrogen transfer reagents	p. 228
Reduction of acetylenes	p. 229
Catalytic hydrogenation	p. 229
Dissolving metals	p. 230
Metal hydrides	p. 230
Hydroboration-protonation	p. 231
Reduction of benzene and derivatives	p. 231
Catalytic hydrogenation	p. 231
Birch reduction	p. 232
Reduction of carbonyl compounds	p. 234
Catalytic hydrogenation	p. 234
Metal hydrides	p. 236
Metal and proton source	p. 253
Hydrogen transfer reagents	p. 255
Reduction of ¿, ß-unsaturated aldehydes and ketone	p. 258
Catalytic hydrogenation	p. 258
Hydride reagents	p. 258
Dissolving metals	p. 260
Reducation of nitro, N-oxides, oximes, azides, nitriles and nitroso compounds	p. 261
Catalytic hydrogenation	p. 261
Metal hydrides	p. 261
Metal and proton source	p. 263
Triphenylphosphine	p. 264
Hydrogenolysis	p. 265
References	p. 266
Oxidation	p. 268
Oxidation of alcohols	p. 268
Chromium (VI)	p. 268
Potassium permanganate	p. 272
Manganese dioxide (MnO2)	p. 273
Dimethylsulfoxide-mediated oxidations	p. 274
Dess-Martin periodinane (DMP)	p. 278
Tetra-n-proplyammonium perruthenate (TPAP)	p. 279
Silver oxide and silver carbonate	p. 280
Oppenauer oxidation	p. 281
Oxidation of aldehydes and ketones	p. 283
Oxidation of phenols	p. 288
Epoxidation	p. 291
Dihydroxylation	p. 297
Aminohydroxylation	p. 301
Oxidative cleavage of C-C double bonds	p. 302
Ozonolysis	p. 303
Glycol cleavage	p. 304
Oxidation of anilines	p. 306
Dehydrogenation	p. 307
Allylic or benzylic oxidation	p. 308
Oxidation of sulfides	p. 308
Oxidation of aliphatic side chains attached to aromatic ring	p. 309
References	p. 311
Pericyclic Reactions	p. 313
Important classes of pericyclic reactions	p. 313
Cycloaddition reactions	p. 313
Electrocyclic reactions	p. 314
Sigmatropic rearrangements	p. 314
Ene reactions	p. 314
Other classes of pericyclic reactions	p. 314
Theoretical explanation of pericyclic reactions	p. 316
MOs and their symmetry properties	p. 316
Suprafacial and antarafacial	p. 322
Conservation of orbital symmetry	p. 324
Cycloaddition reactions	p. 327
[4+2]-Cycloaddition reactions	p. 328
[2+2]-Cycloaddition reactions	p. 331
1,3-Dipolar additions	p. 332
Theoretical explanation	p. 332
Electrocyclic reactions	p. 340
Theoretical explanation	p. 342
General rules for electrocyclic reactions	p. 349
Sigmatropic rearrangements	p. 349
Analysis of sigmatropic rearrangements	p. 355
Carbon shift	p. 358
Ene reactions	p. 360
Selection rules	p. 362
References	p. 362
Index	p. 364
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