Fragment Coupling and the Construction of Quaternary Carbons Using Tertiary Radicals Generated From<i>tert</i>-Alkyl<i>N</i>-Phthalimidoyl Oxalates By Visible-Light Photocatalysis
作者:Gregory L. Lackner、Kyle W. Quasdorf、Gerald Pratsch、Larry E. Overman
DOI:10.1021/acs.joc.5b00794
日期:2015.6.19
visible-light, catalytic Ru(bpy)3(PF6)2, and a reductant fragments to form the corresponding tertiary carbon radical. In addition to reductive coupling with alkenes, substitution reactions of tertiary radicals with allylic and vinylic halides is described. A mechanism for the generation of tertiary carbon radicals from tert-alkyl N-phthalimidoyl oxalates is proposed that is based on earlier pioneering investigations
叔碳自由基与烯烃受体的偶联是结合复杂碳片段并形成新季碳的尚未开发的策略。描述了从叔醇生成亲核叔自由基并在片段偶联反应中利用这些中间体的新方法的范围和局限性。该方法首先将叔醇酰化,得到N-邻苯二甲酰亚氨基草酸叔烷基酯,在可见光催化下Ru(bpy)3(PF6)2和还原剂片段存在,生成相应的叔醇碳自由基。除了与烯烃的还原偶联外,还描述了叔自由基与烯丙基和乙烯基卤化物的取代反应。基于 Okada 和 Barton 的早期开创性研究,提出了一种由 N-邻苯二甲酰亚氨基草酸叔烷基酯生成叔碳自由基的机制。氘标记和竞争实验表明,N-邻苯二甲酰亚氨基草酸叔烷基酯与缺电子烯烃的还原自由基偶联是通过氢原子转移终止的。