A Rational Approach to the Design and Synthesis of Chiral Organopalladium-Amine Complexes

A new chiral auxiliary, (±)-N,N-dimethyl-1-(2,5-dimethylphenyl)ethylamine, was designed and synthesized in two
steps from 1-acetyl-2,5-dimethylbenzene. Its cyclopalladated dimeric complex could be efficiently resolved via the
formation of (S)-prolinate derivatives. Both hand forms of the complex could be obtained in similar yields. Despite
the enormous inter-chelate steric constraints, the bulky monodentate ligand 3,4-dimethyl-1-phenylphosphole (DMPP)
is able to coordinate regiospecifically to the orthopalladated 2,5-dimethylbenzylamine unit trans to the NMe2 group.
Compared to its naphthylamine analogue, the orthopalladated 2,5-dimethylbenzylamine complex exhibits a significantly
higher stereoselectivity in the chiral template promoted asymmetric cycloaddition reaction between DMPP and
ethyl vinyl ketone.