Acknowledgement ix
Supplementory Material x
1 Introduction 1
1.1 Stereoelectronic effects â" orbital interactions in control of structure and reactivity 1
1.2 Orbital interactions in theoretical chemistry 3
1.3 The birth of stereoelectronic concepts in organic chemistry 4
References 6
2 Direct Effects of Orbital Overlap on Reactivity 8
2.1 Bond formation without bond breaking: types of overlap in twoâorbital interactions 9
2.1.1 Factors controlling Ïâbond overlap 12
2.2 Bond formation coupled with bond breaking 25
2.2.1 Threeâorbital interactions: stereoelectronic reasons for the preferred trajectories of intermolecular attack at a chemical bond 25
2.3 Stereoelectronics of supramolecular interactions 29
2.3.1 FMO interactions in intermolecular complexes 29
2.3.2 Expanding the palette of supramolecular interactions: from Hâbonding to Liâ, halogen, pnictogen, chalcogen and tetrel binding 30
References 36
3 Beyond Orbital Overlap: Additional Factors Important for Orbital Interactions. Classifying Delocalizing Interactions 42
3.1 Electronic count: twoâelectron, oneâelectron and threeâelectron bonds 43
3.2 Isovalent vs. sacrificial conjugation 48
3.3 Neutral, negative, and positive hyperconjugation 49
References 52
4 Computational and Theoretical Approaches for Studies of Stereoelectronic Effects 54
4.1 Quantifying orbital interactions 54
4.2 Localized orbitals from delocalized wavefunctions 56
References 60
5 General Stereoelectronic Trends â" Donors, Acceptors, and Chameleons 62
5.1 Three types of delocalization: conjugation, hyperconjugation, and Ïâconjugation 62
5.2 Geminal and vicinal interactions 63
5.3 Stereoelectronic main rule: antiperiplanarity 64
5.3.1 Effects of bond polarity 65
5.3.2 Polarityâinduced acceptor anisotropy 68
5.4 Scales of donor and acceptor ability of orbitals: polarization, hybridization, and orbital energy effects 68
5.4.1 Donors 68
5.4.2 Acceptors 81
5.4.3 Stereoelectronic chameleons: donors masquerading as acceptors 84
5.5 Cooperativity of stereoelectronic effects and antiperiplanar lone pair hypothesis (ALPH) theory â" several donors working together 91
5.6 Summary 92
References 92
6 Stereoelectronic Effects with Donor and Acceptor Separated by a Single Bond Bridge: The Broad Spectrum of Orbital Contributions to Conformational Analysis 97
6.1 Ï/ÏâInteractions 99
6.1.1 Rotational barrier in ethane 99
6.1.2 Axial/equatorial equilibrium in methylcyclohexane 105
6.1.3 The gauche effect 110
6.2 Ï/ÏâInteractions 113
6.2.1 âEclipsedâ and âstaggeredâ conformations of alkenes â" stereoelectronic misnomers 114
6.2.2 Carbonyls 117
6.2.3 Strained bonds 121
6.3 p/ÏâInteractions 122
6.3.1 Primary, secondary, tertiary carbocation stabilization 122
6.3.2 Hyperconjomers of cyclohexyl cations 124
6.3.3 βâSilicon effect and related βâeffects 124
6.4 n/ÏâInteractions 126
6.4.1 Anomeric effects 129
6.4.2 Reverse anomeric effect 142
6.4.3 âAnomeric effects without lone pairsâ: beyond the n â' Ï* interactions 143
6.5 n/ÏâInteractions 147
6.5.1 Esters and related carboxylic acid derivatives 147
6.5.2 Vinyl ethers and enamines 157
6.6 Ï/ÏâInteractions 167
6.6.1 Hyperconjugation in alkynes and its relation to the âabsenceâ of conjugation between two triple bonds in 1,3âdiynes 168
References 170
7 Stereoelectronic Effects with Donor and Acceptor Separated by a Vinyl Bridge 183
7.1 Ï/Ï* interactions 184
7.1.1 Cisâeffect: the case of two Ïâacceptors 184
7.2 Ï/Ï interactions: allenes vs. alkenes 185
7.2.1 Neutral systems 185
7.2.2 Anions 186
7.2.3 Positive conjugation and hyperconjugation in vinyl systems 187
7.2.4 Ï â' Ï* delocalization in allenes: allenyl silanes in reactions with electrophiles 188
7.3 Vinyl halides and their carbanions (transition from ÏCâH â' Ï*CâHal to nc â' Ï*CâHal interactions) 192
7.3.1 Heteroatomâcontaining systems 195
7.4 Diazenes and the isomerization of azo compounds 196
7.5 Antiperiplanarity in coordinated bondâbreaking and bondâforming processes: eliminations, fragmentations and additions 199
7.6 Synâperiplanarity: the second best choice 207
References 208
8 Remote Stereoelectronic Effects 214
8.1 Extended through space interactions: homoconjugation and homohyperconjugation 215
8.1.1 Homoconjugation 215
8.1.2 Homoanomeric effects 217
8.1.3 Crossâhyperconjugation 223
8.2 Double hyperconjugation and throughâbond interactions 223
8.3 Combined throughâbond and throughâspace interactions 228
8.4 Symmetry and cooperativity effects in cyclic structures 229
8.4.1 Hyperaromaticity 229
8.4.2 ÏâAromaticity 230
8.4.3 Double aromaticity 231
References 231
9 Transition State Stabilization with Stereoelectronic Effects: Stereoelectronic Control of Reaction Bottlenecks 236
9.1 Torquoselectivity 240
9.2 Diastereoselection in nucleophilic addition to carbonyl compounds and other Ïâsystems 243
9.3 Electrophilic addition to enamines 245
9.4 Hyperconjugative assistance to alkyne bending and alkyne cycloadditions 246
9.5 Negative conjugation â" donation from oxygen lone pairs to breaking bonds 248
9.6 Remote lone pairs in radical reactions: fragmentations 251
References 254
10 Stereoelectronic Effects in Reaction Design 257
10.1 Static stereoelectronics 257
10.2 Dynamic stereoelectronics 259
References 273
11 Stereoelectronic Effects in Action: The Many Doors Opened by Orbital Interactions 275
11.1 Gauche effect (Ï â' Ï* interactions) 275
11.2 Transâeffect â" the cousin of gauche effect in organometallic chemistry 283
11.3 Anomeric effects (n â' Ï* interactions) 284
11.3.1 Cooperativity and anticooperativity in anomeric systems 288
11.3.2 Spectrum of armed and disarmed glycosides 289
11.3.3 Restoring exoâanomeric effect in carbasugars 294
11.4 Bioorganic chemistry and enzyme reactions 311
References 316
12 Probing Stereoelectronic Effects with Spectroscopic Methods 322
12.1 Infrared spectroscopy 323
12.1.1 Bohlmann effect 323
12.1.2 Redâshifting hydrogen bonds â" an intermolecular version of the Bohlmann effect 331
12.2 Nuclear magnetic resonance spectroscopy 335
12.2.1 Stereoelectronic effects on chemical shifts 335
12.2.2 Diamagnetic effects in 1H NMR 336
12.2.3 Paramagnetic effects in 13C NMR 338
12.2.4 Throughâspace interactions â" γâsubstituent effects 340
12.2.5 Stereoelectronic effects on coupling constants 342
12.3 Conclusion 368
References 368
Index 376
