Copper-catalysed synthesis of alpha-alkylidene cyclic carbonates from propargylic alcohols and CO2

We report a N-heterocyclic carbene copper(I) complex-catalysed formal cycloaddition between readily available propargylic alcohols and carbon dioxide at room temperature. By using the combination of a sterically demanding ^BPDPrCuCl complex (^BPDPr = 1,3-bis(2,6-diisopropylphenyl)-1,3-diazonine-2-ylidene) and CsF, as catalytic system, primary propargylic alcohols are efficiently converted to the corresponding α-alkylidene cyclic carbonates. Gram scale (up to 89% yield) and reusability experiments (74% global yield, turnover number value = 103) showcase the robustness of the catalytic system. This practically simple protocol also tolerates secondary and tertiary propargylic alcohols under CO₂ at atmospheric pressure, enabling the direct synthesis of substituted and unsubstituted α-alkylidene cyclic carbonates at room temperature.