Mechanism of migration of the trimethylsilyl group during reactions of methoxy[(trimethylsilyl)ethoxy]carbene with N-phenylmaleimide and C-60

A novel migration of the trimethylsilyl group during reaction of methoxy[(t rimethylsilyl)ethoxy]-carbene with N-phenylmaleimide (NPM) and with C-60, r eported earlier, was examined by means of deuterium labeling of the carbene . For the NPM case it was found that the CD2CH2SiMe3 group, initially bound to oxygen, became the CH2CD2SiMe3 group bound to carbon in the end product . Not only had the trimethylsilylethyl group moved from oxygen to carbon, b ut the TMS group had also migrated 1,2 along the ethyl chain. For the C-60 case, complete scrambling of the CD2 group was observed, strongly implying the involvement of a silacyclopropane carbocation responsible for product f ormation, The labeling study supports the mechanism that was tentatively ad vanced earlier for addition to NPM and one of the possibilities suggested f or addition to C-60.