It is possible to obtain heterocyclic compounds from the metal catalyzed reactions of a,b-acetylenic carbonyl compounds. In this study, reactions of a,b-acetylenic carbonyl compounds and dimethyldiazomalonate with copper(II) catalyst were investigated. In the presence of copper(II) catalyst, dimethyl diazomalonate is transformed into stable carbenoid intermediate. This intermediate gives electrophilic addition reaction on the carbonyl oxygene to generate ylide intermediate and 1,5-electrocyclization occur over the triple bond of the a,b-acetylenic carbonyl compound. A,b-acetylenic carbonyl compounds may also give [2+1] cheletropic reactions between carbene and triple bond to form cyclopropene derivatives and [3+2] cycloadditions reactions between carbonyl group of the a,b-acetylenic carbonyl compounds and carbene as 1,3-dipolar structure. In 1,5-electrocyclization reactions solvent and type of the catalyst affects the performance of the reaction. Besides that, type of the substituents on the a,b-acetylenic carbonyl compounds and the catalyst is effective on the performance. Any substituent, both electron donating and withdrawing, increases the reaction performance. Only if there are substituted phenyl groups on the a,b-acetylenic carbonyl compounds, substituents of the phenyl are important. Electron donating substituents, such as alkoxy and alkyl, on the phenyl group increase the performance while electron withdrawing substituents, such as halogenes, decrease. On the other hand, steric hindrance of the substituent groups of the a,b-acetylenic carbonyl compounds does not have any effect on the reaction performance. In the performed reactions, dimerization of two diazo compounds has a negative effect on the reaction course. To avoid dimerization, diazo compunds were used less than a,b-acetylenic carbonyl compounds and added slowly to the reaction media.