Arylation of 3-heterylmethylene-5-arylfuran-2(3H)-thiones

Abstract

The behaviour of 3-heterylmethylene-5-arylfuran-2(3 H)-thiones towards the Lewis acid AlCl3 under Friedel–Crafts reaction conditions compared with their oxygen analogues, the furan-2(3 H)-ones is studied. Although the later are known to undergo alkyl/oxygen ring cleavage to give resonance stabilised carbocations which can exhibit either intra- or intermolecular alkylations, furanthiones gave 1, 4-adducts with the furan ring remaining intact. This difference in behaviour is explained in terms of both electronic and steric effects.