Dang Vinh Q, Teets Thomas S
University of Houston, Department of Chemistry 3585 Cullen Blvd. Room 112 Houston TX 77204-5003 USA
Chem Sci. 2023 Aug 18;14(35):9526-9532. doi: 10.1039/d3sc03000h. eCollection 2023 Sep 13.
Visible-light photoredox catalysis is well-established as a powerful and versatile organic synthesis strategy. However, some substrate classes, despite being attractive precursors, are recalcitrant to single-electron redox chemistry and thus not very amenable to photoredox approaches. Among these are carbonyl derivatives, ketones, aldehydes, and imines, which in most cases require Lewis or Brønsted acidic additives to activate photoinduced electron transfer. In this work, we unveil a range of photoredox transformations on ketones and imines, enabled by strongly reducing photosensitizers and operating under simple, general conditions with a single sacrificial reductant and no additives. Specific reactions described here are umpolung C-C bond forming reactions between aromatic ketones or imines and electron-poor alkenes, imino-pinacol homocoupling reactions of challenging alkyl-aryl imine substrates, and γ-lactonization reactions of aromatic ketones with methyl acrylate. The reactions are all initiated by photoinduced electron transfer to form a ketyl or iminyl that is subsequently trapped.
可见光光氧化还原催化作为一种强大且通用的有机合成策略已得到广泛认可。然而，一些底物类别尽管是有吸引力的前体，但对单电子氧化还原化学反应具有抗性，因此不太适合光氧化还原方法。其中包括羰基衍生物、酮、醛和亚胺，在大多数情况下，它们需要路易斯酸或布朗斯特酸添加剂来激活光诱导电子转移。在这项工作中，我们揭示了一系列酮和亚胺的光氧化还原转化反应，这些反应由强还原性光敏剂实现，并在简单、通用的条件下进行，仅使用一种牺牲性还原剂且无需添加剂。这里描述的具体反应包括芳香酮或亚胺与贫电子烯烃之间的极性反转C-C键形成反应、具有挑战性的烷基-芳基亚胺底物的亚胺频哪醇偶联反应，以及芳香酮与丙烯酸甲酯的γ-内酯化反应。这些反应均由光诱导电子转移引发，形成酮基或亚胺基，随后被捕获。
