Ring Opening of Cyclopropanes Catalyzed by an N-Heterocyclic Carbene

Significance

An organocatalytic ring opening of chiral enantioenriched cyclopropanes has been developed. The N-heterocyclic carbene generated in situ from triazolium chloride 1 (5 mol%) and DBU (20 mol%) mediates the redox reaction of trisubstituted formylcyclopropanes 2 with alcohols, thiols or water to give β-substituted carboxylic acid derivatives 3 in high yields and with preservation of the stereochemistry at the β-position. Furthermore, mechanistic considerations based on NMR spectroscopy are provided. Presumably the reaction proceeds via intermediates 4 and 5.