Liquid and solid acids as catalysts for the Thiele–Winter reaction of menadione

Abstract

Liquid acid such as perchloric acid, chlorosulfonic or triflic acid can effectively replace sulfuric acid as a catalyst in Thiele–Winter reaction of menadione. Solid acids like zeolites and heteropolyacids are described for the first time as catalysts in Thiele–Winter reaction. The two step sequence (Thiele–Winter), saponification–oxidation) constitutes a new synthesis of the antibiotic phthiocol from menadione