Rhodium catalysts with cofactor mimics for the biomimetic reduction of CN bonds

A strategy based on the cooperation between metal and bonded cofactor mimics was applied to the transfer hydrogenation of CN bonds. We designed and synthesized a rhodium complex containing a 1,3-dimethylbenzoimidazole moiety, which could transfer hydride from a rhodium center to imine substrates in a biomimetic way. Under both transfer hydrogenation and reductive amination reaction conditions, the catalyst exhibited good selectivity towards CN bonds. With the catalyst, 34 imines were transfer hydrogenated to corresponding amines and a key intermediate of retigabine was prepared via reductive amination in a greener way. According to the NMR observations and isotope experiments, a plausible mechanism for this biomimetic reduction of CN bonds were proposed.