Stereochemical Studies. X. Effects of Neighboring Functional Groups on 1, 2-Asymmetric Induction in the Reduction of Propiophenone Derivatives with Sodium Borohydride

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Effects of neighboring functional groups on 1, 2-asymmetric induction in sodium borohydride reduction were examined with eight kinds of ketones (I-VIII) having functional groups, such as -NH2HCl, -OH, and-OCH3, at a-and/or β-positions to the carbonylgroup. It was recognized that the stereochemical course of the reduction was highlydependent on the position of these functional groups, i. e. erythro-rich products were obtained in reduction of ketones having a functional group at a-position to the carbonyl group, while threo-rich products were obtained in reduction of ketones having a functional group at β-position to the carbonyl group. A six-membered empirical model (XXXVII) was proposed for predicting the stereochemical course in the reduction of ketones having a functional group at β-position to the carbonyl group.Determinations of the relative configurations of the diastereomers (X, XI, XII, XIV, XV, and XVI) were also performed.