Asymmetric Transfer Hydrogenation of α-Substituted-β-Keto Carbonitriles via Dynamic Kinetic Resolution.

A catalytic protocol for the enantio- and diastereoselective reduction of α-substituted-β-keto carbonitriles is described. The reaction involves a DKR-ATH process with the simultaneous construction of β-hydroxy carbonitrile scaffolds with two contiguous stereogenic centers. A wide range of α-substituted-β-keto carbonitriles were obtained in high yields (94%-98%) and excellent enantio- and diastereoselectivities (up to >99% ee, up to >99:1 dr). The origin of the diastereoselectivity was also rationalized by DFT calculations. Furthermore, this methodology offers rapid access to the pharmaceutical intermediates of Ipenoxazone and Tapentadol.