Chromium photocatalysis: accessing structural complements to Diels-Alder adducts with electron-deficient dienophiles.
Chromium photocatalysis: accessing structural complements to Diels-Alder adducts with electron-deficient dienophiles.
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DOI：
10.1039/c6sc03303b
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发表时间：
2017-01-01
期刊：
影响因子：
8.4
通讯作者：
Ferreira EM
中科院分区：
文献类型：
--
作者：
Stevenson SM;Higgins RF;Shores MP;Ferreira EM
报道了铬光催化二烯与缺电子烯烃之间的[4+2]环加成反应，该反应通过三条聚合途径进行，生成“间位”加合物。描述了一种铬催化、可见光活化的双烯与缺电子烯烃之间的网络[4+2]环加成反应。通过对照实验、分离的中间体和测量的氧化还原电位收集的证据表明，提供环己烯加合物的几条聚合反应途径，包括光化学[2+2]环加成/乙烯基环丁烷重排级联和底物激发/氧化序列到自由基阳离子中间体。值得注意的是，伴随的机械论规定导致了一个过程，从传统的Diels-Alder环加成反应生成区域异构体化合物。
A Cr-photocatalyzed [4 + 2] cycloaddition between dienes and electron-deficient alkenes is reported, accessed by up to three converging pathways to yield the “meta” adducts. A chromium-catalyzed, visible light-activated net [4 + 2] cycloaddition between dienes and electron-deficient alkenes is described. Gathered evidence, via 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.