P-Stereogenic Phosphorus Ligands in Asymmetric Catalysis

Chiral phosphorus ligands play a crucial role in asymmetric catalysis for the efficient synthesis of useful optically active compounds. They are largely categorized into two classes: backbone chirality ligands and P-stereogenic phosphorus ligands. Most of the reported ligands belong to the former class. Privileged ones such as BINAP and DuPhos are frequently employed in a wide range of catalytic asymmetric transformations. In contrast, the latter class of P-stereogenic phosphorus ligands has remained a small family for many years mainly because of their synthetic difficulty. The late 1990s saw the emergence of novel P-stereogenic phosphorus ligands with their superior enantioinduction ability in Rh-catalyzed asymmetric hydrogenation reactions. Since then, numerous P-stereogenic phosphorus ligands have been synthesized and used in catalytic asymmetric reactions. This Review summarizes P-stereogenic phosphorus ligands reported thus far, including their stereochemical and electronic properties that afford high to excellent enantioselectivities. Examples of reactions that use this class of ligands are described together with their applications in the construction of key intermediates for the synthesis of optically active natural products and therapeutic agents. The literature covered dates back to 1968 up until December 2023, centering on studies published in the late 1990s and later years.

Palladium/Xiao-Phos-Catalyzed Kinetic Resolution of sec-Phosphine Oxides by P-Benzylation

P-stereogenic tert- and sec-phosphines have wide applications in asymmetric catalysis, materials, and pharmaceutical chemistry, however, their practical synthesis still constitutes a significant challenge. Herein, a successful kinetic resolution of rac-secondary phosphine oxides via the enantioselective P-benzylation process catalyzed by the palladium/Xiao-Phos was designed. Both tert- and sec-phosphine oxides were delivered in good yield and excellent enantiopurity (selectivity factor up to 226.1). The appealing synthetic utilities are further demonstrated by the facile preparation of several valuable P-chiral compounds, precursors of bidentate ligands, as well as transition metal complexes.