Higher Selectivity at Higher Temperatures! Effect of Precursor Stereochemistry on Diastereoselectivity in Radical Allylations. Insight into the Role of the Lewis Acid
作者:Mukund P. Sibi、Tara R. Rheault
DOI:10.1021/ja001456j
日期:2000.9.1
A detailed investigation of the effects of Lewis acid, temperature, and trapping efficiency of functionalized allylstannanes on diastereoselective radical allylation reactions of α-bromooxazolidinone imides 1 and 2 was conducted. Results indicate that despite the addition of Lewis acids, a bidentate chelated radical intermediate 21 may be accessible from only one diastereomer of starting material due
详细研究了路易斯酸、温度和官能化烯丙基锡烷的捕获效率对 α-溴恶唑烷酮酰亚胺 1 和 2 的非对映选择性自由基烯丙基化反应的影响。结果表明,尽管添加了路易斯酸,但由于螯合中间体 17 中不存在的 20 中的空间相互作用,双齿螯合自由基中间体 21 可能只能从起始材料的一种非对映异构体中获得。酸、温度升高和较慢的烯丙基锡烷陷阱都促进了 21 的形成。因此高度立体选择性的自由基烯丙基化(> 50:1,表 2 和 3)可以在室温和低温下进行。