KETENIMINE NITRILE REARRANGEMENTS OF N-ALKOXYKETENIMINES UNDER THEIR GENERATION CONDITIONS

C,C-Substituted N-ethoxyketenimines are extremely unstable even under their generation conditions (dehydrochlorination of N-ethoxyimidoyl ch lorides, dehalogenation of alpha-bromo-N-ethoxyimidoyl halides, the re action of methylmethoxycarbonylketene with N-ethoxytriphenylphosphinim ine) undergo two types of rearrangements: synchronous ring decompositi on down to acetaldehyde and the corresponding CH-nitrile and 1,3-migra tion of the EtO group with formation of alpha-ethoxynitriles. We sugge st that the instability of N-alkoxyketenimines is mainly due to weaken ing of the NO bond as a result of pi(CC)-sigma(NO) hyperconjugation.