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The α-ketol rearrangement is the acid-, base-, or heat-induced 1,2-migration of an alkyl or aryl group in an α-hydroxy ketone or aldehyde to give an isomeric product.〔Paquette, L. A.; Hofferberth, J. E. ''Org. React.'' 2003, ''62'', 477–567. 〕 ==Introduction== Like other ketogenic rearrangements, the α-ketol rearrangement involves the transformation of an alkoxide into a carbonyl group with concomitant movement of the bonding electrons of the migrating group towards an adjacent trigonal center. A distinctive feature of this particular rearrangement, however, is its reversibility—as a result, the more stable α-hydroxy carbonyl compound is favored. A general scheme for the rearrangement is shown below. ''(1)'' This rearrangement differs from similar isomerizations of carbohydrates, which involve the migration of hydrogen and proceed through discrete enediol intermediates. These include the Lobry–de Bruyn–van Ekenstein transformation,〔Gottfried, J.; Benjamin, G. ''Ind. Eng. Chem.'' 1952, ''44'', 141.〕 the Heyns〔Wrodnigg, T. M.; Eder, B. ''Top. Curr. Chem.'' 2001, ''215'', 115.〕 and Amadori rearrangements,〔Hodge, J. ''Adv. Carbohydr. Chem.'' 1955, ''10'', 169.〕 and the Voight〔Voight, K. ''J. Prakt. Chem.'' 1886, 34, 1.〕 and Bilik〔Petrus, L.; Petrusova, M.; Hricoviniova, Z. ''Top. Curr. Chem.'' 2001, ''215'', 15.〕 reactions. α-hydroxy imines may also undergo the rearrangement, although the thermodynamic driving force to amino ketones is often weak (in the absence of protic acids; see below). Advantages: Large thermodynamic energy differences between reactants and products can be harnessed to drive these reactions to completion. Reaction progress can also be influenced through conformational control and often exhibit asymmetric induction. Disadvantages: Because the reaction is reversible and thermodynamically controlled, it cannot be used to synthesize unstable α-hydroxy carbonyl products. Ideal conditions are often difficult to pinpoint and can require extensive catalyst screening. 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「Alpha-ketol rearrangement」の詳細全文を読む スポンサード リンク
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