Chiral oxazoline ligands containing a 1,2,4-triazine ring and their application in the Cu-catalyzed asymmetric Henry reaction

Abstract

Eleven members of new ligand class incorporating a chiral oxazoline and a 1,2,4-triazine ring have been synthesized via Pd-catalyzed amination reaction of 3-halo-1,2,4-triazines with 2-(o-aminophenyl)oxazolines. Buchwald–Hartwig amination of 3-halo-1,2,4-triazines was investigated to establish the best conditions for synthesis of the title ligands. Catalytic activity of the new ligands was evaluated in the asymmetric Henry reaction of nitromethane with a variety of aromatic and aliphatic aldehydes. The β-hydroxy nitroalkanes were obtained in high yields (up to 95%), and moderate-to-good enantioselectivity (up to 82% ee).