Novel approach for catalytic cyclopropanation of alkenes via (2-furyl)carbene complexes from 1-benzoyl-cis-1-buten-3-yne.

The reaction of conjugated ene-yne-ketones 3 with a variety of alkenes in the presence of a catalytic amount of Cr(CO)(5)(THF) at room temperature gives (2-furyl)cyclopropanes in good yields. These cyclopropanation reactions proceed via (2-furyl)carbene-chromium intermediates 4 formed in situ from ene-yne-ketones 3. Late transition metals, such as RuCl(2)(CO)(3), RhCl(cod), PdCl(2), and PtCl(2), also catalyze effectively the cyclopropanation of styrene with 3.