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In the stereochemistry of ketonization of enols and enolates, theory is provided explaining the diastereoselectivity〔(a)"Overlap Control of Carbanionoid Reactions. I. Stereoselectivity in Alkaline Epoxidation," Zimmerman, H. E.; Singer, L.; Thyagarajan, B. S. J. Am. Chem. Soc., 1959, 81, 108-116.(b)Eliel, E., "Stereochemistry of Carbon Compound", McGraw-Hill, 1962 pp 434-436.〕 observed in the conversion of certain enols and enolates into the corresponding ketone. ==Introduction== Ketones and their corresponding enols are isomers, termed tautomers. These are easily interconvertible. But simple enols are not generally stable and of considerably higher energy than the corresponding ketones. Nevertheless, a very large number of organic reactions proceed via enolic intermediates. Thus the behavior of enols is critical to an understanding of myriad organic reactions. Many of these enols, formed in an organic reaction, ''a priori'', can lead onward and afford two diastereomers on ketonization. If one knows the stereochemistry of ketonization of these enolic intermediates, then one can predict the stereochemistry of myriad organic reactions. It was proposed in 1955〔"The Stereochemistry of the Ketonization Reaction of Enols," Zimmerman, H. E. ''J. Org. Chem.'', 1955, 20, 549-557.〕 that the kinetic protonation of enolic species proceeds with an early transition state with the alpha carbon being close to sp2 hybridized. The proton donor selectively approaches the less hindered face of the enolate, thus leading to the less stable of two diastereomers. Reactions controlled in this fashion include: *(a) decarboxylation of malonic acids *(b) decarboxylation of beta-keto acids *(c) the Michael addition of nucleophiles to unsaturated carbonyl compounds *(d) the Birch reduction of enones *(e) the deprotonation – protonation of carbonyl compounds *(f) the dehalogenation of alpha-haloketones *(f) the Norrish Type II Reaction *and many more.〔〔(a) "The Stereochemistry of the Ketonization Reaction of Enols. III," Zimmerman, H. E.; Giallombardo, H. J. ''J. Am. Chem. Soc.'', 1956, 78, 6259-6263.〕〔(b) "The Stereochemistry of Ketonization. IV," Zimmerman, H. E. ''J. Am. Chem. Soc., 1957'', 79, 6554-6558.,〕〔(c) "The Stereochemistry of Ketonization. X. Enols from alpha-Haloacids," Zimmerman, H. E.; Cutshall, T. W. ''J. Am. Chem. Soc.'', 1959, 81, 4305-4308.〕〔(d) "Enhanced Endo-Exo Selectivity in the Stereochemistry of Ketonization of Enols", Zimmerman, H. E.; Linder, L. W. ''J. Org. Chem.'', 1985,c48, 1637-1646.〕〔(e) "Kinetic Protonation of Enols, Enolates and Analogs; The Stereochemistry of Ketonization," Zimmerman, H. E. ''Accounts of Chem. Res.'', 1987, 20, 263-268.〕〔(f) “The Stereochemistry of Allenic Enol Tautomerism; Independent Generation and Reactivity” Zimmerman, H. E.; Pushechnikov, A., Eur ''J. Org. Chem.'', 2006, 15 3491-3497.〕〔(g) “Inter and Intramolecular Stereoselective Protonation of Enols”, Zimmerman, H. E.; Wang, P., ''J. Org. Chem.'' 2002, 69, 9216-9226.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Stereochemistry of ketonization of enols and enolates」の詳細全文を読む スポンサード リンク
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