A Systematic Study on the Bakers’ Yeast Reduction of 2-Oxoalkyl Benzoates and 1-Chloro-2-alkanones

The bakers’ yeast reduction of a series of 2-oxoalkyl arenecarboxylates [R(C=O)CH2O(C=O)C6H4-p-X] (1a–f) (R = CH3 to n-C6H13; X = H) and the phenyl-modified derivatives (1g–l) (R = n-C5H11, X = OH, CH3, F, Cl, Br, or I) as well as 1-chloro-2-alkanones R(C=O)CH2Cl (6a–f) (R = CH3 to n-C6H13) were systematically investigated. The substrate specificities, configuration and %ee of the reduction products were found to be highly dependent on the length of the alkyl group (R) and the α substituent. Thus, the benzoates 1a–f gave optically active 2-hydroxyalkyl benzoates (2a–f) (R, configuration, %ee) (a: CH3, S, 99; b: C2H5, S, 98; c: C3H7, S, 26; d: n-C4H9, R, 55; e: n-C5H11, S, 15; f: n-C6H13, S, 63) in 11–91% yields. Among the modification experiments of the phenyl group, 1g–l, the p-iodo substituent markedly increased the ee from 15 to 71%, although the yield was rather lowered (22% yield). The reduction of α-chloro ketones 6a–f also gave optically active 1-chloro-2-alkanols (7a–f) [(R, configuration, %ee) (a...