Homolytic 1,5-transfer of chiral organosilicon groups from an enoxy oxygen to an alkoxy oxygen--implications for mechanism.

ABSTRACT

Reaction of the optically active silanes, ((Ssi)-(-)-6), formed by treatment of racemic 2-methylenecycloheptanone oxide with LDA followed by (R)-(+)-chloromethyl(1-naphthyl)-phenylsilane, with tributyltin hydride under standard radical conditions affords (2R/2S)-[(S)-(methyl(1-naphthyl)-phensylsilyloxy)methyl]cycloheptanone, (Ssi)-(-)-7, providing strong evidence that homolytic 1,5-transfers of organosilicon groups from enoxy oxygen to alkoxy oxygen proceed with retention of configuration, most likely through a frontside attack mechanism rather than via a hypervalent intermediate.