Stereochemistry of cobalt-catalyzed carbonylation of 2-oxazolines

The stereospecificity of the title reaction is studied using the (4R,5S)-4-methyl-2,5-diphenyl-2-oxazoline and (4R,5R)-4-methyl-2,5-diphenyl-2-oxazoline as the substrates. While the catalyst system containing BnCo(CO)4 and BnCOCo(CO)4 (1) was used initially, a convenient catalyst formulation generated from the commercially available Co2(CO)8 and AIBN (2) has been found more effective than catalyst system 1. The stereoselectivity in all cases favors inversion at the C(5)-position with diastereomeric excess up to >97%.