Decarboxylative [4 + 2] cycloaddition via ligand-to-metal charge transfer photoexcitation of a Cu-MOF

Abstract

Production of p-xylene (PX) via a broad biomass-derived furan cycloaddition has received incremental interest because of its renewable character. To date, the [4 + 2] cycloaddition reaction of furan derivatives with acrylic acid (AA) to synthesize PX has been achieved mainly by thermo-catalysis, but the stern reaction conditions usually lead to high energy costs. Herein, we report a copper-mediated decarboxylative cycloaddition within PW@HKUST-1 under visible-light irradiation to realize rapid synthesis of PX with 92.6% yield in 3 h under atmospheric pressure. Preliminary mechanistic studies reveal a radical decarboxylation process via ligand-to-metal charge transfer (LMCT) that initiates the [4 + 2] cycloaddition under visible-light irradiation. This work suggests that photoexcited [4 + 2] cycloaddition could be a cost-effective strategy for the synthesis of biomass-derived PX.