State Key Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai, 200032, China.
Angew Chem Int Ed Engl. 2016 Oct 10;55(42):13312-13315. doi: 10.1002/anie.201607813.
The polarity reversal (umpolung) reaction is an invaluable tool for reversing the chemical reactivity of carbonyl and iminyl groups, which subsequent cross-coupling reactions to form C-C bonds offers a unique perspective in synthetic planning and implementation. Reported herein is the first visible-light-induced polarity-reversed allylation and intermolecular Michael addition reaction of aldehydes, ketones, and imines. This chemoselective reaction has broad substrate scope and the engagement of alkyl imines is reported for the first time. The mechanistic investigations indicate the formation of ketyl (or α-aminoalkyl) radicals from single-electron reduction, where the Hantzsch ester is crucial as the electron/proton donor and the activator.
极性反转（umpolung）反应是一种非常有价值的工具，可用于反转羰基和亚氨基基团的化学反应性，随后的交叉偶联反应形成 C-C 键，为合成规划和实施提供了独特的视角。本文报道了醛、酮和亚胺的首例可见光诱导的极性反转烯丙基化和分子间迈克尔加成反应。这种选择性反应具有广泛的底物范围，并且首次报道了烷基亚胺的参与。机理研究表明，单电子还原生成酮基（或α-氨基烷基）自由基，其中 Hantzsch 酯作为电子/质子供体和激活剂至关重要。
