The reactions of α-ylidene (vinylidene, benzylidene, styrylmethylidene) bis[carbonyls] with copper mono/bis[carbonylcarbenoids]

The [Cu(acac) ₂]-catalyzed reactions of various α,β,γ,δ-unsaturated bis-ketones/bis-esters/bis-keto esters with dimethyl diazomalonate and ethyl diazoacetate were studied. Total steric/electronic convenience of the present reaction paths was investigated. Methoxy/nitro substituents in m-/p-positions on benzylidene biscarbonyls did not alter the general routes of the reactions, supporting concerted mechanism. Dihydrobenzoxepine/oxepine formation was sterically sensitive to the related pre-ring conformation, and dihydrofurans were effected by both charge control and steric factors.