Cooperative Transition-Metal and Chiral Brønsted Acid Catalysis

asymmetric catalysis - hydrogenation - imines - iron

Significance

The authors report a protocol for the enantioselective hydrogenation of various ketimines in the presence of a chiral Brønsted catalyst and a well-defined nonchiral iron catalyst. This work demonstrates that enantioselective reduction reactions with hydrogen can be performed without employing precious-metal catalysts and chiral ligands yielding products with high yields and enantioselectivities.

Comment

NMR spectroscopic studies revealed the formation of complex 1 when a 1:1 mixture of TRIP and the Knölker iron complex (cat. 1) were mixed. Upon addition of a ketimine to the reaction mixture, the formation of complex 2 was observed. These results suggest that a cooperative catalytic system is operative for this transformation.