Acid-catalyzed Cyclization of Chalcones derived from Various Nitrogenous Heteroaromatic Compounds

Abstract

2-(2-Furfurylidene) acetylquinoxaline (Ia) and its 3-methyl analog (Ib) were cyclized to pyrrolo [1, 2-α] quinoxaline ring systems (IIa and IIb) by hydrochloric acid treatment. 2-(4-Methoxybenzylidene) acetylpyridine could be cyclized directly to the 2, 3-dihydroindolizine ring system (V) by treatment with perchloric acid. 2-Arylideneacetyl-3-methyl-quinoxalines (IX) also were cyclized to the corresponding pyrrolo [1, 2-α] quinoxaline systems by hydrochloric acid or perchloric acid. The cyclization of 2-(2-furfurylidene)-acetylquinoline (XI) was performed by using acetic anhydride in the presence of a catalytic amount of trifluoroacetic acid. 2-(2-Furfurylidene) acetylpyrazine (XIII) was cyclized easily by hydrochloric acid treatment. The structures of the adducts of these cyclic products with dimethyl acetylenedicarboxylate are discussed.