Free radical hydrostannylation of unactivated alkenes with chiral trialkylstannanes

摘要

Free radical hydrostannylation of olefins with differing steric and electronic demands have been carried out using the chiral, nonracemic stannanes (1R,2S,5R)-menthyldiphenyltin hydride (7), bis[(1R,2S,5R)-menthyl]phenyltin hydride (8), and tris[(1R,2S,5R)-menthyl]tin hydride (9). These reactions resulted in adducts 16-18 with yields that were found to depend on the nature of the substituents on both alkene and stannane and could be carried out at low temperature initiated by triethylborane and oxygen; MenPh_2SnH (7) reacted with tert-butyldimethyl(1-phenylvinyloxy)silane (1) at -78 °C to afford adduct 19 in near-quantitative yield. Somewhat surprisingly, addition of small quantities of diphenyl diselenide to these reactions failed to improve the outcome under any circumstances.