ONE-STEP ROUTE TO FLUORINATED FURO[2,3-B]QUINOXALINES

The reaction of 6,7-difluoro-1-ethylquinoxalinium salts with 2,4-penta nedione, ethyl and bornyl acetoacetates and other beta-keto esters res ults in the formation of luoro-3a,4,9,9a-tetrahydrofuro[2,3-b]quinoxal ines. In addition, asymmetric 6-fluoro-7-morpholino and 6-fluoro-7-thi omorpholino substituted 1-ethylquinoxalinium salts react with alkyl ac etoacetates in a regio- and stereoselective manner, thus giving exclus ively the corresponding alkyl 2-methyl-6-fluoro-7-substituted 3a,4,9,9 a-tetrahydrofuro [2,3-b]quinoxalin-3-carboxylates.