An efficient approach to the synthesis of 4H-1-benzothiopyran-4-ones via intramolecular Wittig reaction

Abstract

The reaction of S-acyl(aroyl)thiosalicylic acids 2 with N-phenyl(triphenylphosphoranylidene)ethenimine 3 in stepwise fashion leads to the acylphosphoranes 5 which subsequently undergo intramolecular Wittig cyclization on the thiolester carbonyl to afford the 4H-1-benzothiopyran-4-ones 7 in excellent yields.