The Voight reaction on tertiary α-hydroxy ketones

Abstract

The Voight reaction is for the transformation of secondary α-hydroxy ketones into corresponding α-amino ketones. Although discovered as early as 1886, it has not enjoyed wide popularity in organic synthesis, as it is applicable to only secondary α-hydroxy ketones. In terms of extending the applications of the reaction, we have shown that the reaction takes place on tert-α-hydroxy ketones also, particularly when present on rigid planar molecular frameworks like phenanthrene, pyrene and acenaphthylene. The reaction is not a simple substitution of the hydroxy group with amines, but goes through imine formation followed by 1,2-C migration. The reaction provides good opportunity for the synthesis of optically active α-amino ketones. We have achieved facile synthesis of some chromatographically separable and optically active tert-α-amino ketones by employing S-(−) or R-(+)-α-methylbenzylamines in the Voight amination.