Chiral auxiliaries - Principles and recent applications

Abstract

With modern methods for asymmetric catalysis breaking ground, the use of chiral auxiliaries seems to be old-fashioned and rather inefficient. However, for many transformations, chiral auxiliaries often represent the only selective method available. In addition, high levels of selectivity and reliability are often attractive characteristics of chiral auxiliaries and allow for the efficient and rapid synthesis of desired chiral compounds. In addition, even in cases with imperfect selectivity, the use of an attached chiral auxiliary allows the enrichment of diastereoselectivity, and hence enantioselectivity after removal of the auxiliary, by many standard separation techniques. This article gives an overview on the most important classes of chiral auxiliaries, discussing the mode of action and highlighting some recent applications. It does not deal with the use of chiral catalysts, chiral reagents or achiral auxiliaries. © Georg Thieme Verlag Stuttgart.