Mechanism and Stereoselectivity of the Aza-Wittig Reaction between Phosphazenes and Aldehydes
作者:Fernando P. Cossío、Concepción Alonso、Begoña Lecea、Mirari Ayerbe、Gloria Rubiales、Francisco Palacios
DOI:10.1021/jo0525884
日期:2006.3.31
The mechanism of the aza-Wittig reaction between phosphazenes and aldehydes has been studied computationally, using DFT methods (B3LYP/6-31G* level), and experimentally. It has been found that the reaction consists of a tandem [2+2] cycloaddition−cycloreversion sequence in which π and σ orbitals as well as lone pairs are involved. Both [2+2] processes take place via thermally allowed supra-supra mechanisms
使用DFT方法(B3LYP / 6-31G *级)并通过实验对磷腈与醛之间的aza-Wittig反应机理进行了计算研究。已经发现反应由串联的[2 + 2]环加成-环还原序列组成,其中涉及π和σ轨道以及孤对。既[2 + 2]流程经由热允许同上发生-同上机制。P -三甲基- λ 5个-phosphazenes被预测为比它们的反应性更强P -三苯基类似物。整个反应的立体化学结果仅取决于第二步骤中,因为在中间1,3,2-λ构象变化5-草氮磷氮杂环丁烷的活化能比第二个[2 + 2]环还原反应低得多。预测了相应的(E)-亚胺的优先或排他性形成。