Carboxylates as Nucleophiles in the Enantioselective Ring-Opening of Formylcyclopropanes under Iminium Ion Catalysis

In this work, carboxylic acids, which are typically regarded as poor nucleophiles, are demonstrated to be competent reagents to promote the ring-opening of formylcyclopropanes after activation of the latter through iminium ion formation. Under optimized reaction conditions, a variety of gamma-acyloxy-substituted aldehydes can be obtained in high yields and enantioselectivities through the desymmetrization of substituted meso-formylcyclopropanes in the presence of a chiral secondary amine as catalyst.