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Carboxylation of Aryl Triflates with CO₂ Merging Palladium and Visible-Light-Photoredox Catalysts

Bhunia, Samir Kumar, Das, Pritha, Nandi, Shantanu, Jana, Ranjan
Organic letters 2019 v.21 no.12 pp. 4632-4637
ambient temperature, carbon dioxide, carboxylation, carboxylic acids, catalysts, chemical structure, drugs, electron transfer, estrone, iridium, palladium, phenol, reducing agents, spectroscopy, synthesis
We report herein a visible-light-promoted, highly practical carboxylation of readily accessible aryl triflates at ambient temperature and a balloon pressure of CO₂ by the combined use of palladium and photoredox Ir(III) catalysts. Strikingly, the stoichiometric metallic reductant is replaced by a nonmetallic amine reductant providing an environmentally benign carboxylation process. In addition, one-pot synthesis of a carboxylic acid directly from phenol and modification of estrone and concise synthesis of pharmaceutical drugs adapalene and bexarotene have been accomplished via late-stage carboxylation reaction. Furthermore, a parallel decarboxylation–carboxylation reaction has been demonstrated in an H-type closed vessel that is an interesting concept for the strategic sector. Spectroscopic and spectroelectrochemical studies indicated electron transfer from the Ir(III)/DIPEA combination to generate aryl carboxylate and Pd(0) for catalytic turnover.