The reaction of selenenyl halides with wittig reagents

The transylidation reactions of PhSeBr with two equivalents of an alkylidene-triphenylphosphorane give selenophosphoranes, Ph3P=CRSePh. These also can be obtained by treating the corresponding selenophosphonium salts, prepared by quarternization of triphenylphosphine with PhSeCHRBr, with n-BuLi. The selenophosphoranes react with aldehydes in situ (Wittig reaction) to give the expected vinylic selenides in good yields. The stereochemistry of the reactions is discussed.