Interaction of 3-ethoxycarbonyl(carboxy)-substituted 5,6,7,8-tetrafluorochromones with N-nucleophiles: synthesis of fluorocoumarins

Polyfluorobenzopyranopyrazoles (isoxazoles) have been prepared via cyclizat ion of 5-tetrafluorophenyl-4-ethoxycarbonyl(carboxy)pyrazoles (isoxazoles) produced by the reaction of 3-ethoxycarbonyl-2-methyl- and 3-carboxy-substi tuted 5,6,7,8-tetrafluorochromone with hydrazine(hydroxylamine). It has bee n found that 3-ethoxycarbonyl-2-methyl-5,6,7,8-tetrafluorochromone forms th e corresponding 2-ethylidenamino-substituted 1,3-keto esters with ammonia a nd benzylamine, from which 3-ethylidenamino-4-oxy-5,6,7,8-tetrafluorocoumar ins were readily obtained. In contrast to the non-fluorinated analogues, 3- ethoxycarbonyl-2-methyl-5,6,7,8-tetrafluorocoumarins were found to undergo acyl-lactone transformation into coumarin structures under acidic condition s. (C) 1999 Elsevier Science S.A. All rights reserved.