Synthesis of Chiral Heterocyclic Phosphines for Application in Asymmetric Catalysis

Abstract

The synthesis of chiral heterocyclic phosphines, such as phosphiranes, phosphetanes, phospholes and phosphinanes will be reviewed. These compounds play a pivotal role as ligands and organocatalysts, respectively, in asymmetric reactions. Synthetic approaches will be analyzed in the framework of several sub-categories e.g. the preparation of mono-, bis- and poly(phosphines). General synthetic strategies for the preparation of large families of related compounds will be considered such as 1.) stereoselective -alkylation of phosphine oxides or phosphine boranes, 2.) ring closure by substitution reactions and 3.) hydrogenations of unsaturated P-heterocylic compounds, followed by epimerization reactions. Besides these general methodologies also protocols leading to a single phosphine will be discussed. In some cases also the preparation of such phosphines will be presented, which have not yet been used in asymmetric catalysis, however, which have - owing to their structure - some relevance to synthetic methodologies or compounds discussed herein. For most phosphines presented applications in asymmetric catalytic reactions will be briefly mentioned together with characteristic enantioselectivities achieved.