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Helvetica Chimica Acta, vol.96, no.3, pp.488-493, 2013 (SCI-Expanded)
The [Cu(acac)2]-catalyzed reactions of several tertiary enaminones with three diazocarbonyl compounds, i.e., dimethyl diazomalonate, ethyl diazoacetoacetate, and ethyl diazoacetate, yielded amino- and additionally carbonyl-substituted dihydrofurans, together with further furan derivatives. Due to the conjugation of α-carbonyl/α-Ph groups, reactions proceeded only via 1,5-electrocyclization of corresponding keto-ylides. On the other hand, in the absence of any α-substituent, tertiary enaminone and ethyl diazoacetate, reacted via an accompanying mechanism by a push-pull cyclopropane intermediate, to yield a 2,4-dicarbonyl-substituted furan in one step with moderate yield. Copyright © 2013 Verlag Helvetica Chimica Acta AG, Zürich, Switzerland.