Chemoselective Catalytic Dehydrogenation of Benzylic Amines Driven by the TEtraQuinoline/FeCl2 Complex

A chemoselective dehydrogenation protocol for benzylic amines catalyzed by the TEtraQuinoline (TEQ)/FeCl2 complex is described. In combination with 2 equiv of tert-butyl hydroperoxide, as little as 0.1 mol% of catalyst loading was sufficient to convert primary and secondary benzylic amines to the corresponding imines and dimerized imines, respectively. Subsequent hydrolysis of the imines allowed for removal of the benzyl group on the nitrogen atom. Nonaromatic carbon-carbon multiple bonds and the O-Bn group remained intact in the present protocol, providing a complementary deprotection procedure to reductive removal conditions exerted by Pd catalysis.

Automated summary

A chemoselective dehydrogenation protocol for benzylic amines using the TEtraQuinoline (TEQ)/FeCl2 complex catalyst was developed. By combining with 2 equiv of tert-butyl hydroperoxide, as low as 0.1 mol% catalyst loading was sufficient to convert primary and secondary benzylic amines to the corresponding imines and dimerized imines. The benzyl group on the nitrogen atom could be removed through subsequent hydrolysis of the imines, while nonaromatic carbon-carbon multiple bonds and the O-Bn group remained intact, providing a complementary deprotection procedure to reductive removal conditions exerted by Pd catalysis.