One-step route to fluorinated furo[2,3-b]quinoxalines

The reaction of 6,7-difluoro-1-ethylquinoxalinium salts with 2,4-pentanedione, ethyl and bornyl acetoacetates and other β-keto esters results in the formation of 6,7-difluoro-3a,4,9,9a-tetrahydrofuro[2,3-b]quinoxalines. In addition, asymmetric 6-fluoro-7-morpholino and 6-fluoro-7-thiomorpholino substituted 1-ethylquinoxalinium salts react with alkyl acetoacetates in a regio- and stereoselective manner, thus giving exclusively the corresponding alkyl 2-methyl-6-fluoro-7-substituted 3a,4,9,9a-tetrahydrofuro[2,3-b]quinoxalin-3-carboxylates.