The Anomeric Effect and Related Stereoelectronic Effects at Oxygen

The anomeric effect is a well-defined and much studied example of a deep seated and very general effect in organic chemistry. It involves a fundamental interaction between the lone pair electrons of oxygen and the antibonding orbitals of adjacent bonds, which can control not only conformation but also reactivity in suitable systems. So the heart of this book is a consideration of the properties of non-bonding pairs of electrons, and the influence of orbital orbital interactions on structure and reactivity. I have been lucky in recent months to be able to discuss various matters arising in this book with people who know more about them than I do. Parti cularly Professors C. Altona, A. Eschenmoser, F. Hirshfeld, M. Lahav, R.A. McClelland, G.M. Sheldrick and A. Vos, and, nearer horne, I. Fleming, P.G. Jones, AJ. Stone (who helped with the rather theoretical Appendix) and I.H. Williams. I am also most grateful to Professors P. Deslongchamps, ID. Dunitz, D.G. Gorenstein, W.P. Jencks, G.A. Jeffrey, R.D. Lemieux and S. Wolfe, for very helpful correspondence, and information in advance of pUblication. I have covered the literature received in Cambridge up to early December 1981.

Texte du rabat

The anomeric effect is a well-defined and much studied example of a deep­ seated and very general effect in organic chemistry. It involves a fundamental interaction between the lone pair electrons of oxygen and the antibonding orbitals of adjacent bonds, which can control not only conformation but also reactivity in suitable systems. So the heart of this book is a consideration of the properties of non-bonding pairs of electrons, and the influence of orbital­ orbital interactions on structure and reactivity. I have been lucky in recent months to be able to discuss various matters arising in this book with people who know more about them than I do. Parti­ cularly Professors C. Altona, A. Eschenmoser, F. Hirshfeld, M. Lahav, R.A. McClelland, G.M. Sheldrick and A. Vos, and, nearer horne, I. Fleming, P.G. Jones, AJ. Stone (who helped with the rather theoretical Appendix) and I.H. Williams. I am also most grateful to Professors P. Deslongchamps, ID. Dunitz, D.G. Gorenstein, W.P. Jencks, G.A. Jeffrey, R.D. Lemieux and S. Wolfe, for very helpful correspondence, and information in advance of pUblication. I have covered the literature received in Cambridge up to early December 1981.

Contenu
A. Stereoelectronic Effects on Structure.- 1. Introduction.- 2. The Anomeric Effect.- 3. The Reverse Anomeric Effect.- 4. The Exo-Anomeric Effect.- 5. The Generalised Anomeric Effect.- 6. The Gauche Effect.- B. The Electronic Basis of the Effects.- 1. Introduction.- 2. The Status of Lone Pair Electrons.- 3. Calculations on X?Y Systems.- 4. Effects on Bond Lengths and Angles.- 5. Effects in Furanoses.- 6. The Stereoelectronic Basis of the Anomeric Effect.- 7. Related Stereoelectronic Effects.- C. Stereoelectronic Effects on Reactivity: The Kinetic Anomeric Effect.- 1. Introduction.- 2. Reactions of the Acetal Group.- 3. The Hydrolysis of Orthoesters.- 4. Carbonyl-Oxygen Exchange Reactions of Esters and Amides.- 5. The Hydrolysis of Imidate Esters: Stereoelectronic Effects at Oxygen and Nitrogen.- 6. Reactions of Phosphate Esters.- 7. Radical Reactions.- 8. Enzyme Reactions.- D. Appendix.- 1. Canonical Lone Pair Description.- 2. Hybrid Lone Pair Description.- E. References.- F. Subject Index.