The application of the chiral ligand DTBM-SegPHOS in asymmetric hydrogenation

Abstract

This paper summarizes the application of the chiral ligand DTBM-SegPHOS in asymmetric catalytic hydrogenation reactions. DTBM-SegPHOS exhibits pronounced catalytic activity and enantioselectivity due to its high electron density and steric bulk. Indeed, it often performs better in reactions in which traditionally used ligands provide poor results. According to the impressive influence of the t-Bu groups of DTBM-SegPHOS and the resulting interactions with various substrates, new substrates bearing t-Bu groups were studied in asymmetric hydrogenations which were not previously possible. The ligand QuinoxP*, which possesses similar structural features to that of DTBM-SegPHOS, was employed for the hydrogenation of such substrates with the best results. The mechanistic studies prove that the unique catalytic behaviors of the complexes of these ligands in asymmetric hydrogenation are a result of the extensive network of weakly attractive interactions between the catalyst and substrate in the transition states. An overview of these impressive ligands in various asymmetric hydrogenations using different transition metal catalysts is provided.