Stevenson Susan M, Higgins Robert F, Shores Matthew P, Ferreira Eric M
Department of Chemistry , University of Georgia , Athens , GA 30602 , USA . Email:
Department of Chemistry , Colorado State University , Fort Collins , CO 80523 , USA.
Chem Sci. 2017 Jan 1;8(1):654-660. doi: 10.1039/c6sc03303b. Epub 2016 Sep 12.
A chromium-catalyzed, visible light-activated net [4 + 2] cycloaddition between dienes and electron-deficient alkenes is described. Gathered evidence, control experiments, isolated intermediates, and measured redox potentials, points to several converging reaction pathways that afford the cyclohexene adducts, including a photochemical [2 + 2] cycloaddition/vinylcyclobutane rearrangement cascade and a substrate excitation/oxidation sequence to a radical cation intermediate. Notably, the accompanying mechanistic stipulations result in a process that yields regioisomeric compounds from those generated by traditional Diels-Alder cycloadditions.
本文描述了一种铬催化、可见光活化的二烯与缺电子烯烃之间的净[4 + 2]环加成反应。收集到的证据、对照实验、分离出的中间体以及测量的氧化还原电位表明，有几种汇聚的反应途径可生成环己烯加合物，包括光化学[2 + 2]环加成/乙烯基环丁烷重排级联反应以及底物激发/氧化生成自由基阳离子中间体的序列。值得注意的是，伴随的机理规定导致了一个过程，该过程产生的区域异构体化合物与传统狄尔斯-阿尔德环加成反应生成的化合物不同。
