Ketenimine-nitrile rearrangements of N-alkoxyketenimines under their generation conditions
摘要:
C,C-Substituted N-ethoxyketenimines are extremely unstable even under their generation conditions (dehydrochlorination of N-ethoxyimidoyl chlorides, dehalogenation of alpha-bromo-N-ethoxyimidoyl halides, the reaction of methylmethoxycarbonylketene with N-ethoxytriphenylphosphinimine) undergo two types of rearrangements: synchronous ring decomposition down to acetaldehyde and the corresponding CH-nitrile and 1,3-migration of the EtO group with formation of alpha-ethoxynitriles. We suggest that the instability of N-alkoxyketenimines is mainly due to weakening of the NO bond as a result of pi(CC)-sigma(NO)* hyperconjugation.
An Efficient Method for Generation of α-Oxoketenes: Cycloreversion of Enolized Meldrum's Acid Derivatives
作者:Masayuki Sato、Hitoshi Ban、Chikara Kaneko
DOI:10.1016/s0040-4039(97)01566-9
日期:1997.9
synthesized from Meldrum'sacids. These dioxinones underwent 4+2 cycloreversion to methoxy- or siloxycarbonylketenes and ketones quantitatively at 20–50 °C. The ketenes were characterized by IR spectroscopy as well as by trapping with t-butanol. The ready cycloreversion of these enolized Meldrum'sacid derivatives strongly indicates that the anomalouslyhigh susceptibility of Meldrum'sacids to nucleophilic