Synthesis of 4‐Hydroxy‐5‐methyl‐ and 4‐Hydroxy‐6‐methylcyclohexenones by PdII‐Catalyzed Oxidation and Lipase‐Catalyzed Hydrolysis

Abstract

AbstractA short route for the syntheses of methyl‐substituted hydroxycyclohexenones, which are building blocks for various natural products, is presented. Both oxygen atoms were introduced as acetates by a palladium(II)‐catalyzed 1,4‐addition to a 1,3‐diene. The distinction between the two acetoxy groups was achieved by regioselective monohydrolysis with lipase from Candida rugosa, which gave 1‐acetoxy‐4‐hydroxy‐5‐methylcyclohexene and its 6‐methyl regioisomer as a separable mixture. The target compounds 4‐hydroxy‐5‐methylcyclohex‐2‐enone and 4‐hydroxy‐6‐methylcyclohex‐2‐enone could then be obtained as diastereomeric mixtures in good overall yields and with moderate enantiomeric excesses (31–67 %).