Photochemical activity of a key donor-acceptor complex can drive stereoselective catalytic α-alkylation of aldehydes
Photochemical activity of a key donor-acceptor complex can drive stereoselective catalytic α-alkylation of aldehydes
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DOI：
10.1038/nchem.1727
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发表时间：
2013-09-01
期刊：
影响因子：
21.8
通讯作者：
Melchiorre, Paolo
中科院分区：
文献类型：
--
作者：
Arceo, Elena;Jurberg, Igor D.;Melchiorre, Paolo
阳光驱动的光化学过程的不对称催化变体在可持续制备手性分子方面具有非凡的潜力。然而，任何光化学反应固有的短寿命电子激发态的参与使得手性催化剂难以决定产物的立体化学。在此，我们报道了在热不对称过程中具有众所周知用途的现成手性有机催化剂，也能够在可见光驱动的具有合成相关性的分子间碳 - 碳键形成反应中提供高水平的立体控制。提出了一种独特的催化机制，其中催化剂积极参与底物的光化学活化（通过诱导手性电子给体 - 受体复合物的瞬时形成）以及决定立体选择性的过程。我们利用这种方法实现了在热条件下极其困难的转化，例如醛与烷基卤化物的不对称α - 烷基化、全碳季碳立体中心的形成以及远程立体化学的控制。
Asymmetric catalytic variants of sunlight-driven photochemical processes hold extraordinary potential for the sustainable preparation of chiral molecules. However, the involvement of short-lived electronically excited states inherent to any photochemical reaction makes it challenging for a chiral catalyst to dictate the stereochemistry of the products. Here, we report that readily available chiral organic catalysts, with well-known utility in thermal asymmetric processes, can also confer a high level of stereocontrol in synthetically relevant intermolecular carbon-carbon bond-forming reactions driven by visible light. A unique mechanism of catalysis is proposed, wherein the catalyst is involved actively in both the photochemical activation of the substrates (by inducing the transient formation of chiral electron donor-acceptor complexes) and the stereoselectivity-defining event. We use this approach to enable transformations that are extremely difficult under thermal conditions, such as the asymmetric a-alkylation of aldehydes with alkyl halides, the formation of all-carbon quaternary stereocentres and the control of remote stereochemistry.