Lewis-acid promoted aromatic cyclization of α-chlorosulfides: Synthesis of ethyl isothiochroman-1-carboxylate and related compounds

A variety of ethyl isothiochroman-1-carboxylates and related compounds were synthesized by treatment of 2-chloro-2-[(2-arenyl)ethylthio]acetates with stannic chloride in methylene chloride. The same procedure was applied to the synthesis of ethyl 4-chloro-4-methyltetrahydrothiopyran-2-carboxylate. Some isothiochroman-1-carboxylic acids were prepared and evaluated for antiinflammatory activity. Among the compounds tested, 7-phenoxyisothiochroman-1-carboxylic acid showed weak activity.