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Photo-induced Decarboxylative Heck-Type Coupling of Unactivated Aliphatic Acids and Terminal Alkenes in the Absence of Sacrificial Hydrogen Acceptors

Cao, Hui, Jiang, Heming, Feng, Hongyu, Kwan, Jeric Mun Chung, Liu, Xiaogang, Wu, Jie
Journal of the American Chemical Society 2018 v.140 no.47 pp. 16360-16367
acrylates, aromatic hydrocarbons, byproducts, carbon dioxide, carboxylic acids, catalysts, feedstocks, hydrogen, oxidants, silanes
1,2-Disubstituted alkenes such as vinyl arenes, vinyl silanes, and vinyl boronates are among the most versatile building blocks that can be found in every sector of chemical science. We herein report a noble-metal-free method of accessing such olefins through a photo-induced decarboxylative Heck-type coupling using alkyl carboxylic acids, one of the most ubiquitous building blocks, as the feedstocks. This transformation was achieved in the absence of external oxidants through the synergistic combination of an organo photo-redox catalyst and a cobaloxime catalyst, with H₂ and CO₂ as the only byproducts. Both control experiments and DFT calculations supported a radical-based mechanism, which eventually led to the development of a selective three-component coupling of aliphatic carboxylic acids, acrylates, and vinyl arenes. More than 90 olefins across a wide range of functionalities were effectively synthesized with this simple protocol.