Asymmetric Deoxygenative Formal [3 + 2] Cycloaddition of Carboxylic Acids and Vinylcyclopropanes

We report an iridium-catalyzed asymmetric formal [3 + 2] cycloaddition between carboxylic acids and vinylcyclopropanes to access highly enantioenriched tetrahydrofurans. This reaction proceeds under mild conditions with excellent stereoselectivity and a broad substrate scope. A key feature of the method is the in situ formation of mixed anhydrides, which modulate the reactivity of carboxylic acids and prevent undesired O-nucleophilic pathways. The transformation is compatible with diverse functional groups, complex bioactive molecules, and late-stage carbon isotope labeling using [13C]CO2. This work expands the utility of carboxylic acids in enantioselective cycloaddition chemistry.