Starting from the respective tertiary α-silylmethyl amines, the intramolecular cyclization of α-aminoalkyl radicals to Michael acceptors produced tetrahydroisoquinolines. The reaction conditions included the use of 5 mol% of an iridium photoredox catalyst, dimethylformamide as the solvent, and equimolar amounts of water and cesium carbonate as the additives. 13 substrates were synthesized from ortho-alkylbenzaldehydes in a three-step procedure involving a carbonyl condensation, a radical bromination, and a substitution by a secondary α-silylmethyl amine. After optimization of the photocyclization, the reaction delivered tetrahydroisoquinolines in moderate to high yields (41–83%). A facial diastereoselectivity (dr ≅ 80:20) was observed with chiral substrates and a crystal structure provided evidence for the relative configuration of the major diastereoisomer. A catalytic cycle with direct electron transfer to the photoexcited metal catalyst is proposed.

中文翻译：

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通过可见光介导的 α-氨基烷基自由基的 6-exo-trig 环化合成四氢异喹啉

从各自的叔α-甲硅烷基甲基胺开始，α-氨基烷基自由基与迈克尔受体的分子内环化产生四氢异喹啉。反应条件包括使用5 mol%的铱光氧化还原催化剂，二甲基甲酰胺作为溶剂，以及等摩尔量的水和碳酸铯作为添加剂。在涉及羰基缩合、自由基溴化和仲 α-甲硅烷基甲基胺取代的三步程序中，从邻烷基苯甲醛合成了 13 种底物。在优化光环化后，该反应以中等至高产率（41-83%）提供四氢异喹啉。面部非对映选择性（dr ≅ 80：20) 用手性底物观察到，晶体结构为主要非对映异构体的相对构型提供了证据。提出了一种将电子直接转移到光激发金属催化剂的催化循环。