Experimental and quantum-mechanical investigation of the vinylsilane-iminium ion cyclizationElectronic supplementary information (ESI) available: experimental procedures, spectroscopic data and copies of 13C NMR spectra for compounds 4–16. Selected bond lengths in geometry optimized structures of α-substituted (Z)-vinylsilanes. Cartesian coordinates, raw energies and lower frequencies of computationally characterized species 17A–32H. See http://www.rsc.org/suppdata/ob/b2/b212333a/
作者:Lisbet Kværnø、Per-Ola Norrby、David Tanner
DOI:10.1039/b212333a
日期:2003.3.13
underlined the lack of reactivity of ketiminium species and also convincingly explained the observed diastereoselectivities of aldiminium species. The calculations further revealed that (Z)-vinylsilanes cyclize via a silicon-stabilized beta-carbocation, and that any formal aza-Cope rearrangement of the starting material to an allylsilane-iminium species does not take place in a concerted fashion. However
实验研究了涉及衍生自胺6和7的亚胺鎓类物种的乙烯基硅烷-酮亚胺离子环化反应,作为一些生物学上令人感兴趣的1-azaspirocycle的可能方法。然而,即使在高温下微波辐射的条件下,也未观察到这样的环化,而(与先前的结果一致)相应的乙烯基硅烷-醛亚胺离子环化更成功。在由6衍生的前体的环化反应中,用α取代氮取代的Aldiminium物种没有表现出非对映选择性,而对于7衍生的亚胺鎓物种则可以获得高反式非对映选择性。对一般反应机理的量子力学研究强调了酮亚胺物种缺乏反应性,也令人信服地解释了醛亚胺物种的非对映选择性。该计算进一步表明,(Z)-乙烯基硅烷通过硅稳定的β-碳化反应环化,并且起始原料到烯丙基硅烷-亚胺基物种的任何正式的氮杂-科普重排都不以一致的方式发生。然而,计算表明,对于相应的(E)-乙烯基硅烷,氮杂-Cope重排在环化之前,与(Z)-异构体的环化相比,总的反应在能量上稍差。并且起始材