Copper‐Catalyzed Bis(methoxycarbonyl)carbene Reactions of α , β ‐Unsaturated Carboxamides

The [Cu(acac) 2 ]‐catalyzed reactions of α , β ‐unsaturated carboxamides with dimethyl diazomalonate yielded dihydrofuran derivatives by a 1,5‐electrocyclic reaction at C( β ), and butadiene derivatives by carbene addition reaction at C( α ) ( Schemes 4 and 5 ; Table ). Phenyl substituents at the N‐atom of the amides seem to be effective on the reaction pathways ( Table ).