Thermally-Induced 1,2-Shifts To Convert Olefins to Carbenes: Does Silicon Do It? If So, Why Not Carbon?
作者:Thomas J. Barton、Jibing Lin、Sina Ijadi-Maghsoodi、Martin D. Power、Xianping Zhang、Zhongxin Ma、Hideaki Shimizu、Mark S. Gordon
DOI:10.1021/ja00152a010
日期:1995.11
be reported for an olefin-to-carbene rearrangement. The analogous all-carbon system failed to ring expand. Ab initio calculations revealed that this was opposite to any predictions which would be made from ring strain considerations. Calculations showed that for silyl migration the transition state was late and was actually the carbene, while for carbon migration the TS was early and considerably higher
通过实验和理论研究了通过 1,2-甲硅烷基转移将烯烃热异构化为卡宾。对于无环乙烯基硅烷,没有发现这种重排的证据,也无法在顺式、反式异构化中识别出硅的电子辅助。2,4-二甲基-1, 3-二硅杂环丁烷的偶然合成允许对其气相热环膨胀进行动力学检查,以生成 2-亚甲基-1,3-二硅杂环戊烯。Arrhenius 参数(log A = 12.48,Esub act} = 54.09 kcal/mol)是第一个报告的烯烃到卡宾重排的参数。类似的全碳系统未能环扩。Ab initio 计算表明,这与根据环应变考虑做出的任何预测相反。计算表明,对于甲硅烷基迁移,过渡态较晚,实际上是卡宾,而对于碳迁移,TS 较早且能量比所得卡宾高得多。重新检查了 2-亚甲基-1-硅杂环丁烷重排,发现在低于通过卡宾 TS 扩环所需的温度下发生 1,4-双基的可逆开环。45 个参考文献,5 个图,1 个标签。