Intramolecular Crossed [2+2] Photocycloaddition through Visible Light-Induced Energy Transfer

作者：Jiannan Zhao, Jonathan L. Brosmer, Qingxuan Tang, Zhongyue Yang, K. N. Houk, Paula L. Diaconescu, Ohyun Kwon · 发表于：Journal of the American Chemical Society · 年份：2017 · DOI：10.1021/jacs.7b05277 · 被引用次数：148 · 研究领域：Radical Photochemical Reactions、Catalytic C–H Functionalization Methods、Oxidative Organic Chemistry Reactions

Herein, we present the intramolecular [2+2] cycloadditions of dienones promoted through sensitization, using a polypyridyl iridium(III) catalyst, to form bridged cyclobutanes. In contrast to previous examples of straight [2+2] cycloadditions, these efficient crossed additions were achieved under irradiation with visible light. The reactions delivered desired bridged benzobicycloheptanone products with excellent regioselectivity in high yields (up to 96%). This process is superior to previous syntheses of benzobicyclo[3.1.1]heptanones, which are readily converted to B-norbenzomorphan analogues of biological significance. Electrochemical, computational, and spectroscopic studies substantiated the mechanism of triplet energy transfer and explained the unusual regiocontrol.