Sulfonyl‐stabilized phosphonium ylids

Two general methods are given for the synthesis of mono‐sulfonyl‐substituted methylenephosphoranes, magnified image ( 1 ). (i) Methylenetriphenylphosphorane can be substituted by using sulfonyl fluorides to give 1. A similar reaction with sulfonyl chlorides, however, fails mostly, (ii) The synthesis of sulfonylmethyltriphenylphosphonium bromides ( 5 ) from bromomethyl sulfones and triphenylphosphine, due to Speziale and Ratts , was improved. The bromides 5 were readily transformed to 1 by base. As an extension of (i), the reaction of benzylidenetriphenylphosphoranes with sulfonyl halides has been studied. Contrary to previous reports it was found that the product from ethoxycarbonylmethylenetriphenylphosphorane and tosyl chloride is α‐ethoxycarbonyl‐ p ‐tolylthiomethylenetriphenylphosphorane, instead of the corresponding tosyl compound. Method (i), however, does not apply to ethoxycarbonylmethylenetriphenylphosphorane ( 16 ).