U.S. Army Edgewood Chemical Biological Center APG, Maryland 21010-5424, USA.
J Org Chem. 2010 Apr 16;75(8):2510-7. doi: 10.1021/jo902600y.
Aziridines are useful precursors to the azomethine ylide family of 1,3-dipoles whose cycloaddition chemistry has been extensively exploited in the synthesis of heterocyclic targets. The torquoselectivity of aziridines that lack a plane of symmetry was investigated as an essential component of the calculation of the overall relative reaction rates and in prediction of the stereochemistry of the 2,3-trans compounds in 1,3-dipolar cycloaddition chemistry. It has been found at the MP2(Full)/6-311++G(d,p)//MP2(Full)/6-31+G(d) level that outward rotation is preferred for electronegative or anionic substituents while electropositive and cationic substituents favor inward rotation. After consideration of frontier molecular orbital theory, inductive, resonance, and electrostatic effects, an explanation of the preferred direction of rotation during ring cleavage that is based on substituent electron-withdrawing ability by means of a polar effect is presented.
氮丙啶是亚甲胺叶立德 1,3-二极体家族的有用前体，其环加成化学在杂环靶标的合成中得到了广泛的应用。缺乏对称面的氮丙啶的扭转选择性作为计算整体相对反应速率和预测 1,3-偶极环加成化学中 2,3-反式化合物立体化学的重要组成部分进行了研究。已经在 MP2(Full)/6-311++G(d,p)//MP2(Full)/6-31+G(d)水平上发现，对于电负性或阴离子取代基，外旋转是优选的，而对于正电性和阳离子取代基，内旋转是优选的。在前缘分子轨道理论、诱导、共振和静电效应的考虑之后，提出了一种基于取代基吸电子能力通过极效应来解释环裂解过程中旋转方向的优先性的解释。
