Asymmetric Hydrogenation of 3-Arylindenones to Chiral Indenols via 6-Carbazole-Modified Chiral Ir-SpiroPAP Catalysts

A series of 6-carbazole-modified Ir-SpiroPAP catalysts were designed for the asymmetric hydrogenation of indenones to chiral indenols. The optimized catalyst, featuring a 6-carbazole moiety on the pyridine ring and 3,5-dimethyl groups on the P-phenyl rings, achieved up to 98% yield, 95% ee, and an impressive turnover number (TON) of 7200. Density Functional Theory (DFT) analyses revealed that the 6-carbazole unit enhances catalyst rigidity, influencing enantioselectivity by inducing geometric distortion of the indenones during the hydrogenation process.