Synthesis of fluorinated furo- and pyrrolo[3,4-b]quinoxaline 4,9-dioxides

The reaction of 5,6-difluorobenzofuroxane 1 with ethyl acetoacetate in the presence of triethylamine results in the formation of 2-methyl-3-ethoxycarbonyl-6,7-difluoroquinoxaline 1,4-dioxide 2 which was converted consequently into the bromomethyl 3 and acetoxymethyl 4 derivatives; hydrolysis of the latter with hydrochloric acid gave furo[3,4-b]quinoxaline 4,9-dioxide 5. Compound 3 was transformed by the action of ammonia and primary alkyl amines into 2-substituted 1,3-dihydro-2H-pyrrolo[3,4-b]quinoxaline 4,9-dioxides 6 and further into the corresponding 6-amino compounds 7 and 8.