Reactions of Enaminones with Diazocarbonyl Compounds

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.