Copper-catalyzed multicomponent assembly of gamma-butenolides via the interception of carbonyl ylides with iminium ions

A Cu(i)-catalyzed three-component reaction of cyclopropenes, enamines and aldehydes has been realized. This reaction proceeds via the interception of carbonyl oxonium ylide intermediates with alpha, beta-unsaturated iminium ions that are in situ generated from enamines and aldehydes under the catalysis of Cu(MeCN)(4)PF6, leading to the desired gamma-butenolide derivatives in good yields and with moderate diastereoselectivities. Access to these derivatives with tethered ketone and alkynal groups will expand the structural diversity of multi-substituted butenolides.