Origin of diastereoselectivity in the thermal [4+2] cycloadditions of dienophiles derived fromOppolzer's sultams: Stericvs. Stereoelectronic Influences
作者:Christian Chapuis、Jean-Yves De Saint Laumer、Maurus Marty
DOI:10.1002/hlca.19970800115
日期:1997.2.10
coefficients are nonequivalent with respect to both X(α)-re and X(α)-si faces, and thus have, depending on the conformation, a matching or mismatching stereoelectronic influence with the co-operative steric effect. This dissymmetry is believed to result from the generalized anemone effect of the N lone pair, itself anomerically stabilized and directed, in the absence of crucial steric interactions, by the pseudo-axial
含有结构部分SO 2 NC(O)X(α)= Y(β)的天生苏丹草衍生的双亲物的比较半经验PM3和从头算STO 3-21G计算表明,在低能构象物中,热力学上较少稳定SO 2 / C(O) -顺式,C(O)/ X = YS-顺式构象也LUMO能级和原子系数方面的反应性。此外,X(α),Y(β)LUMO原子系数是不等价相对于两个X(α)-Re和X(α) - SI面,因此取决于构象,具有配合的或错配的立体电子影响与合作的空间效应。据信这种不对称性是由于N孤对的广义海葵效应引起的,N孤对本身在没有关键的空间相互作用的情况下通过假轴反平面外SO键被自身稳定和定向。五Ñ酰基取代bornanesultams电弧讨论(( - ) - 1A:ñ -丙烯酰基,XCH,YCH 2 ;( - ) - 1B ; Ñ -crotonoyl,XCH,YCHMe;( - ) - 1C:NN '-fumaroyl, XCH,