Several cyclic enamines with five to seven-memberedrings react with 2-(1,2-diphenyl-3-cyclopropenylidene)propanedinitrile to give medium ringcompounds, showing that the latter is a versatile reagent which can insert three carbon atoms between α- and β-carbons of cyclic enamines. These medium ringcompounds undergo transannular reactions on treatment with hydrochloric acid to yield fulvene derivatives with