The Mechanism of the Mitsunobu Reaction. III. The Use of Tributylphosphine

Abstract

³¹P n.m.r . studies indicate that, when tributylphosphine is used in the Mitsunobu esterification reaction, clean formation of a single intermediate, an alkoxyphosphonium carboxylate, is apparent. In the absence of acid, at least two species are observed, a dialkoxytributylphoshorane and the corresponding alkoxyphosphonium salt. The order of mixing of the reagents can dramatically change the mechanism and stereochemistry of esterification reactions.