Studies on K2CO3-Catalyzed 1,4-Addition of 1,2-Allenic Ketones with Diethyl Malonate: Controlled Selective Synthesis of β, γ-Unsaturated Enones and α-Pyrones

The reaction of diethyl malonate with various substituted 1,2-allenic ketone can be catalyzed by 10% of K2CO3leading to polyfunctionalized β, γ-unsaturated enones 3 or 4. With 3-unsaturated 1-substituted-1, 2-allenic ketones, the highly selective formation of β, γ-unsaturated enones 4 was observed; with 1,2-allenic ketones with one or two γ-substituents, only β, γ-unsaturated enones 3 with an unmigrated carbon-carbon double bond were produced; with γ-monosubstituted-1,2-allenic ketones the corresponding (E)-3 were formed highly selectively; with propadienyl ketones, a mixture of β, γ-unsaturated enones 3 and 4 were formed.……