From Photoredox Catalysis to the Direct Excitation of EthynylBenziodoXolones: Accessing Alkynylated Quaternary Carbons from Alcohols via Oxalates

Abstract

EthynylBenziodoXolones (EBXs) are commonly used as radical traps in photocatalytic alkynylations. Herein, we report their application in two complementary deoxygenation strategies allowing the synthesis of valuable alkynylated all-carbon quaternary centers from tertiary alcohols via stable oxalate salts. Our first approach involves a photocatalytic process using 4CzIPN as an organic dye to promote oxidative degradation of the oxalate and EBXs to trap the formed radical. In our second approach, we demonstrate the direct photoexcitation of an EBX, which then acts as both oxidant and radical trap, alleviating the need for a photocatalyst in several EBX-mediated alkynylation processes.In addition, we would like to thank members of the Laboratory of Supramolecular Chemistry-Ecole Polytechnique Fédérale de Lausanne LCS-EPFL: Cristian Pezzato and Cesare Berton for enabling us to run our absorption and fluorescence studies and Ophélie Planes who also helped greatly for the cyclic voltammetry studies.