Benzenesulfonylcarbonitrile oxide. 5. Face selectivity of cycloaddition to chiral terminal alkenes

Abstract

The diastereomer ratio for cycloaddition of benzenesulfonylcarbonitrile oxide (BSNO) to a series of (S)-vinylglycine-derived alkenes varied from 30:70 to 66:34 depending on the substitutents at the chiral center. Isomer ratios were routinely determined by 1H-NMR; isolation confirmed the results in several cases. Isomer assignment was based on comparison to acivicin where the absolute configuration has been determined by X-ray analysis. The results are interpreted as consistent with competitive cycloaddition to the alkene oriented in two differing conformations. © 1984.