Nitric Acid → 3-(Difluoromethoxy)-2,4,5-trifluoro-6-nitrobenzoic acid

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Reaction Steps

20 ml of concentrated aqueous nitric acid (d=1.42) were added dropwise, whilst stirring and cooling with water, to a solution of 15.0 g (0.062 moles) of 3-difluoromethoxy-2,4,5-trifluorobenzoic acid [(XXV), X=X'=F] (prepared as described in Preparation 1, 2 or 3) in 40 ml of concentrated aqueous sulfuric acid, and the mixture was stirred at 60° C. for 7 hours. At the end of this time, it was allowed to stand to cool to room temperature, and then the reaction mixture was poured into ice-water, and extracted with diethyl ether. The extract was washed with a saturated aqueous solution of sodium chloride and dried over anhydrous sodium sulfate; the solvent was then removed by evaporation under reduced pressure, to give 16.6 g of 3-difluoromethoxy-2,4,5-trifluoro-6-nitrobenzoic acid as a yellow powder, melting at 77°-80° C.

Provenance & Evidence