| |
[摘要]：DFT calculations have been performed to study the mechanism and diastereoselectivity aspects of aziridination reactions of arsenic ylides. The reactions of three different arsenic ylides, unstabilized (H), semistabilized (Ph) and stabilized (COMe) arsenic ylides, with an imine have been considered. For all three arsenic ylides, the transoid mode of addition is more favoured than the cisoid mode of addition. The inherent stability differences between the addition transition-state geometries are governed by steric interactions induced by the ylidic substituents and the methyl group of the carbamate and weak C-H center dot center dot center dot O hydrogen-bonding interactions. For both the semistabilized and stabilized arsenic ylides, the trans selectivity is determined exclusively by the elimination transition states. The formation of trans-aziridine is explained on the basis of weak hydrogen-bonding interactions and steric interactions. |
|
