Rhodium-Catalyzed Asymmetric Reductive Hydroformylation of α-Substituted Enamides

Chiral gamma-amino alcohols are prevalent structural motifs in natural products and bioactive compounds. Nevertheless, efficient and atom-economical synthetic methods toward enantiomerically enriched gamma-amino alcohols are still lacking. In this study, a highly enantioselective rhodium-catalyzed reductive hydroformylation of readily available alpha-substituted enamides is developed, providing a series of pharmaceutically valuable chiral 1,3-amino alcohols in good yields and excellent enantioselectivities in a single step. The development of the 4,4 '-bisarylamino-substituted BIBOP ligand is crucial for the success of this transformation. DFT calculations and experimental data have revealed the importance of hydrogen bonding between the N-H group in the structure of TFPNH-BIBOP and the enamide carbonyl group in promoting both high enantioselectivity and reactivity. This method has enabled the concise synthesis of several chiral pharmaceutical intermediates including a single-step synthesis of the key chiral intermediate of maraviroc.