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.