Asymmetric Hydrogenation with MCM-41-Supported Pincer Catalysts

An MCM-41-supported unsymmetrical, optically active pincer rhodium complex, MCM-Rh, was prepared for the asymmetric hydrogenation of alkenes. Thus, the reaction of (E)-­diethyl 2-benzylidene succinate (1) was carried out with 0.1 mol% Rh of MCM-Rh under hydrogen atmospheric conditions to give 99% ee of (S)-2 in 96% conversion with 7680 h-¹ of TOF. The catalyst was readily recovered by centrifugation and reused four times without loss of catalytic activity. In contrast, the reaction with a homogeneous counterpart homo-Rh afforded 99% ee of (R)-2 with 500 h-¹ of TOF under similar conditions.