烯酮与亚甲胺环加成反应的一种新反应机制

A NEW REACTION SCHEME OF THE CYCLOADDITION OF KETENE AND METHYLENIMINE

烯酮与亚甲胺之间发生环加成反应可以生成氮杂环丁酮: 关于这个反应的机理,目前还未见报导。我们用从头计算分子轨道法,在RHF/3-21G的水平,研究了上述反应的机理,同时采用内禀反应坐标法(IRC)得出了反应途径。

The reaction mechanism of the cycloaddition of ketene to methylenimine is Investigated by using ab initio SCF MO method at the level of RHF/3-21G. Intrinsic reaction coordinate (IRC) method is used to trace the reaction path. The results show that this reaction is a nonsychronous, concerted reaction. The activation barrier is calculated to be 109.9kJ/mol (MP2/3-21G result). In the course of reaction, rotation of methylene group instead of oxygen in ketene is ascertained. This result indicates that the reaction mechanism proposed formerly for similar reaction H_2C=C=O+H_2C=CH_2 has to be revised.