Direct diastereoselective introduction of l-menthol residue into 1,2,4-triazin-5(4H)-one

Abstract

The reaction of 3-phenyl-1,2,4-triazin-5(4H)-one (1) with l-menthol in the presence of aliphatic acid anhydrides results in (6S)- and (6R)-1-acyl-6-(l-menth-3-yl)-1,6-dyhydro-3-phenyl-1,2,4-triazin-5(4H)-ones. The reaction is diastereoselective with predominant formation of (6S)-isomers. The reaction diastereoselectivity increases with enhancement of the steric hindrance in the vicinity of the reaction center of the azine.