Recent investigations have shown that the stereochemistry of radical reactions could be controlled without using chiral auxiliaries. The development was achieved mainly in the radical conjugate addition promoted by chiral Lewis acids, which formed the chiral environment by coordinating the substrates. However, there have been no reports on asymmetry induction in radical reactions through a π-stacking and/or hydrogen bonding chiral environment.
We herein report on the development of an enantioselective radical addition reaction to acylhydrazones for preparing enantioenriched amines with ammonium salts of cinchona alkaloid derivatives. The addition reactions of alkyl halides to various acylhydrazones of aldehydes were performed, affording addition adducts in high chemical yields with high enantioselectivities.