Recent developments in transition metal-catalyzed asymmetric borrowing hydrogen catalysis

Abstract

Asymmetric Borrowing Hydrogen (BH) catalysis is a versatile, one-step approach for synthesizing enantioenriched amines/carbonyl derivatives from biomass-derived oxidized hydrocarbons with water as the sole by-product. These valuable chiral moieties are ubiquitous in natural products, fragrances, agrochemicals, and pharmaceuticals; hence, efficient methodologies that can directly form C–C and C–N bonds to diversify the synthetic utility are highly desired. Over the last decade, numerous contributions involving noble metals have been documented in this area, which largely relies on the choice of a suitable transition metal catalyst that facilitates a succession of oxidation/reduction steps. Only very recently, 3d metals were utilized for C–C and C–N bond formation in an asymmetric manner using the BH strategy. This article describes the current state-of-the-art for controlling the stereochemistry in the formation of a new stereogenic center via multiple catalysis, rational ligand design, etc. Several other strategies are outlined, such as asymmetric reductive functionalization, dynamic kinetic resolution, enantioconvergent processes, etc. New chiral catalysts based on 3d metals are anticipated to arise and find applications in the field of asymmetric borrowing hydrogen catalysis.