Phosphonium Salt Organocatalysis

Abstract

Abstract The field of organocatalysis is growing rapidly and attracts an increasing number of research groups. Most organocatalysts can be classified as Lewis bases, Lewis acids, Brønsted acids and Brønsted bases. However, examples of Lewis acid organocatalysis under homogeneous conditions are comparatively rare. Phosphonium salts are easily accessible and frequently used intermediates in organic synthesis, long known phase‐transfer catalysts and potential Lewis acid organocatalysts. This review covers the application of phosphonium salts as Lewis acidic catalysts for a variety of CC, CO and CN bond‐forming reactions under homogeneous conditions. Moreover, recent developments are included which show the potential of chiral phosphonium salts as asymmetric (phase‐transfer) catalysts.