A chiral cobalt(ii) complex catalyzed asymmetric formal [3+2] cycloaddition for the synthesis of 1,2,4-triazolines

Abstract

A highly efficient catalytic asymmetric formal [3+2] cycloaddition reaction of 5-alkoxyoxazoles with azodicarboxylate compounds has been realized by a chiral N,N′-dioxide/Co(BF₄)₂·6H₂O complex. A series of poly-substituted 1,2,4-triazolines compounds were obtained in moderate to excellent yields (70–99%) with excellent enantioselectivities (82–98% ee).