O-Chlorosulfenylbenzoyl Chloride: A Useful Reagent in the Synthesis of Thioxanthones

Abstract

Thioxanthen-9-one derivatives have been shown to possess useful medicinal properties such as anti-histaminic¹, antiparasitic², neuroleptic³ and anti-tumour activity⁴. Two general approaches have up to now been used for their preparation. The first relies on the well-known reaction of various substituted thio-phenols with halo-arenes to produce diphenyl thio-ethers (Ullmann reaction) which are then cyclized in sulfuric acid to produce the corresponding thioxanthones. The other method is based on the reaction of either thio-salicylic acid or 2,2′-dithioalicylic acid with a substituted arene in concentrated sulfuric acid⁵.