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

Abstract

1-Cinnamoylisoquinoline (I) was treated with perchloric acid in ethanol to give 2, 5-dihydro-1-oxo-3-phenyl-[1H] pyrrolo [2, 1-α] isoquinolinium perchlorate (V) in the yield of 48.1%. V was derived to 1-(4-nitrobenzoyloxy)-3-phenyl-[1H] pyrrolo [2, 1-α] isoquinoline (VI) by means of the Shotten-Baumann reaction. 3-Methylquinoxalin-2-yl 4-phenyl-1, 3-butadienyl ketone (VIIa) was treated with acid to give 3-hydroxy-4-methyl-1-styrylpyrrolo [1, 2-α] quinoxalinium perchlorate (VIIIa) in quantitative yield. VIIIa was treated with diazomethane to give 3-methoxy-4, 5-dimethyl-1-styrylpyrrolo [1, 2-α] quinoxalinium perchlorate (XI). VIIIa gave a monobromide (XIIa) on treatment with bromine in carbon tetrachloride. The rate of acid-catalyzed cyclization of 3-methylquinoxalin-2-yl 4-(4-nitrophenyl)-1, 3-butadienyl ketone (VIIb) was slower than that of VIIa. Attempts to cyclize XIV intramolecularly to 2, 5-dihydro-1-phenylpyrrolizin-3 [1H]-one (XVI) were unsuccessful under various conditions.