The Anomeric Effect and Related Stereoelectronic Effects at Oxygen

ISBN-13: 9783642686788 / Angielski / Miękka / 2012 / 152 str.

A. J. Kirby

Opis

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.

Spis treści

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.- a. Sulphur Compounds.- b. Transmission through Phosphorus.- c. Transmission through Sulphur.- 6. The Gauche Effect.- B. The Electronic Basis of the Effects.- 1. Introduction.- 2. The Status of Lone Pair Electrons.- a. Evidence from Hydrogen-bonding.- b. Electron Density Measurements.- 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.- a. The Structure of CH2F2.- b. Bonding in ROCH2X.- c. Bonding and Restricted Rotation in Dimethoxymethane.- d. The Generalised Anomeric Effect.- e. The Reverse Anomeric Effect.- f. The Exo-Anomeric Effect.- 7. Related Stereoelectronic Effects.- a. The Anomeric Effect at sp2 centres.- b. The Gauche Effect.- C. Stereoelectronic Effects on Reactivity: The Kinetic Anomeric Effect.- 1. Introduction.- a. The Use of sp3-hybrid Lone Pairs.- b. The Stereoelectronic Basis of the Kinetic Anomeric Effect.- 2. Reactions of the Acetal Group.- a. Acetal Hydrolysis.- b. Acetal Formation.- c. Acetal Oxidation.- 3. The Hydrolysis of Orthoesters.- a. Hemiorthoesters.- 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.