Regio- and Stereoselective 1,3-Dipolar Cycloadditions to 6<i>H</i>-1,2-Oxazines Leading to New Heterobicyclic Compounds
作者:Hans-Ulrich Reissig、Elmar Schmidt、Reinhold Zimmer
DOI:10.1055/s-2006-942403
日期:2006.6
exclusive formation of exo-configured products. 6H-1,2-Oxazines are therefore sufficiently reactive and selective dipolarophiles. The regioselectivity of the 1,3-dipolar cycloadditions is briefly discussed considering steric and electronic effects. PM3 calculations did not lead to fully satisfactory results in predicting the observed high regioselectivities. Preliminary subsequent reactions of the heterobicyclic
典型的 1,3-偶极子,如腈氧化物、亚胺和叶立德,以及重氮烷烃、硝酮和甲亚胺叶立德,通常与 6H-1,2-恶嗪发生平滑的 [3+2] 环加成反应。杂双环加合物以中等至非常好的收率获得,具有优异的区域选择性和高非对映选择性。6H-1,2-恶嗪的 6-乙氧基取代基强烈地屏蔽了一个面,因此导致几乎完全形成外构型产品。因此,6H-1,2-恶嗪具有足够的反应性和选择性。考虑到空间和电子效应,简要讨论了 1,3-偶极环加成的区域选择性。PM3 计算在预测观察到的高区域选择性方面并未导致完全令人满意的结果。