Synthesis of 1,2-diazepino[3,4-b]quinoxalines and pyrido[3′,4′:9,8][1,5,6]oxadiazonino[3,4-b]quinoxalines via a 1,3-dipolar cycloaddition reaction

The reaction of 6-chloro-2-(1-methylhydrazino)quinoxaline 4-oxide 8 with furfural, 3-methyl-2-thiophene-carbaldehyde, 2-pyrrolecarbaldehyde, 4-pyridinecarbaldehyde and pyridoxal hydrochloride gave 6-chloro-2-2-(2-furylmethylene)-1-methylhydrazino]quinoxaline 4-oxide 5a , 6-chloro-2-1-methyl-2-(3-methyl-2-thienyl-methylene)hydrazino]quinoxaline 4-oxide 5b , 6-chloro-2-1-methyl-2-(2-pyrrolylmethylene)hydrazino]quinoxa-line 4-oxide 5c , 6-chloro-2-1-methyl-2-(4-pyridylmethylene)hydrazino]quinoxaline 4-oxide 5d and 6-chloro-2-2-(3-hydroxy-5-hydroxymethyl-2-methyl-4-pyridylmethylene)-1-methylhydrazino]quinoxalme 4-oxide 5e , respectively. The reaction of compound 5a or 5b with 2-chloroacrylonitrile afforded 8-chloro-3-(2-furyl)-4-hydroxy-1-methyl-2,3-dihydro-1H-1,2-diazepino3,4-b]quinoxaline-5-carbonitrile 6a or 8-chloro-4-hydroxy-1-methyl-3-(3-methyl-2-thienyl)-2,3-dihydro-1H-1,2-diazepino3,4-b]quinoxaline-5-carbonitrile 6b , respectively, while the reaction of compound 5e with 2-chloroacrylonitrile furnished 11-chloro-7,13-dihydro-4-hydroxy-methyl-5,14-methano-1,7-dimethyl-16-oxopyrido3′,4′:9,8]1,5,6]oxadiazonino3,4-b]quinoxaline 7.