Bidentate Ligands Containing a Heteroatom–Phosphorus Bond

Abstract

Bidentate phosphorus ligands containing one or more heteroatom-phosphorus bonds are of high interest because they are relatively easy to prepare, and because a huge multitude of inexpensive, commercially available chiral diols, diamines, amino alcohols and amino acids can serve as the scaffold. Although the heteroatoms in these scaffolds are usually electronegative in nature, the reactivity and enantioselectivity of the metal complexes based on some of these ligands are quite remarkable, and sometimes even surpass those of the complexes based on electron-rich phosphines. This chapter compiles the comprehensive data concerning the asymmetric hydrogenation of various prochiral olefins mediated by the rhodium(I) complexes of this class of chiral ligands. Aminophosphine-Phosphinites (AMPPs)The ease of synthesis from chiral amino alcohols with a wide array of derivatives in one step established its good potential in the field of asymmetric catalysis. The general preparation of "semi-symmetrical" AMPPs involves the nucleophilic attack of two equivalents of chlorophosphine in the presence of a base (Fig. 27.1). A "mixed" AMPP can also be prepared by virtue of the fact that phosphorus-based electrophiles have a strong preference for hydroxy over secondary amine or amide. Clearly, this synthetic method allows the preparation of a large variety of AMPP ligands with adjustable electronic and steric properties. Agbossou recently reviewed the state of the art of AMPPs [1]. In consideration to the modern high-throughput methods, this approach allowed a rapid combinatorial screening of various catalysts and reactions.In general, applications of AMPP have concentrated on the asymmetric hydrogenation of functionalized olefins, especially dehydroamino acids. Among 883The Handbook of Homogeneous Hydrogenation. Edited by J. G. de Vries and C. J. Elsevier