Efficient dual catalytic enantioselective diethylzinc addition to the exocyclic CN double bond of some 1,2,4-N-triazinylarylimines using polymer-supported chiral β-amino alcohols derived from norephedrine

Chiral N,N-dialkylnorephedrines and their corresponding copolymers were examined as chiral ligands for the enantioselective diethylzinc addition to the exocyclic CN double bond of some 4-arylideneamino-3-mercapto-6-methyl-4H-1,2,4-triazin-5-ones 2a-f in the presence of Lewis acid as activator. The corresponding 4-(1-arylpropyl)amino-3-mercapto-6-methyl-4H-1,2,4-triazin-5-ones 4a-f were obtained in high yields with high enantioselectivities using chiral polymers (up to 91% ee), which are almost the same as those obtained from homogeneous analogues (92% ee). Reductive cleavage of the 1,2,4-traizinyl heterocyclic ring led smoothly to the corresponding free primary aromatic amines 11 without significant loss of enantiomeric purity.