Electrophilic Addition of Propargylic Cations to Allenes: Formation of Crowded Chloro- and Azido-Enynes by Trapping of the Resulting Allylic Cations with TMSX (X = Cl, N<sub>3</sub>): A Synthetic and Computational Study
作者:Kenneth K. Laali、Ganesh C. Nandi、Gabriela L. Borosky、G. G. K. S. Narayana Kumar
DOI:10.1002/ejoc.201300553
日期:2013.8
promote this reaction with similar conversions and stereoselectivity. Although trapping with TMSBr and TMSI gave intractable mixtures, trapping with TMSN3 in a couple of cases led to the isolation of the corresponding isomeric azido-enynes, albeit in lower isolated yields and lower stereoselectivity. Competitive formation of the Meyer-Schuster rearrangement products was also observed. Sterically crowded
通过炔丙醇与催化量的 Bi(OTf)(3) 电离产生的炔丙阳离子与芳基取代的丙二烯反应生成初始烯丙阳离子,这些阳离子在 TMSCl 存在下被淬灭,形成许多空间拥挤的氯-烯炔作为 Z 和 E 异构体的混合物,强烈偏爱 Z 烯烃。其他几种金属三氟甲磺酸盐 M(OTf)(3) (M = Sc, Yb, La) 以及硝酸铋 Bi(NO3)(3)5H(2)O 也以类似的转化率和立体选择性促进该反应。尽管用 TMSBr 和 TMSI 捕获会产生难以处理的混合物,但在一些情况下用 TMSN3 捕获会导致相应异构叠氮烯炔的分离,尽管分离产率和立体选择性较低。还观察到 Meyer-Schuster 重排产物的竞争性形成。空间拥挤的氯丙二烯不会与炔丙醇形成加合物,而是在 Bi(OTf)(3) 的影响下发生骨架重排,形成 2-氯丁二烯。DFT 计算结果表明炔丙基阳离子的相对反/同步能和 Z/E 异构产物之间的能