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%.