Reactivity of vinyl sulphonic esters. Part XII. Cyclisation of arylsulphonylvinyl sulphonates to benzo[b]thiophen 1,1-dioxides. A novel 1,2-sulphonyl shift

Abstract

trsns-2-Arylsulphonyl-1,2-diphenylvinyl p-bromobenzenesulphonates containing a methyl or a chloro-substituent in the aryl residue, on treatment with boron trifluoride, gave 2,3-diphenylbenzo[b]thiophen 1,1-dioxides. The position of the substituent in the products indicated that a rearrangement had occurred during the cyclisation. The formation of a spirothieten 1,1-dioxide intermediate and a subsequent 1,2-sulphonyl shift are proposed to rationalise the rearrangement.