Trifluoroacetic acid → 7-(methyloxy)-6-(trifluoromethyl)-2H-1,4-benzoxazin-3(4H)-one

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Reaction Steps

Ethyl {[5-(methyloxy)-2-nitro-4-(trifluoromethyl)phenyl]oxy}acetate (0.71 g, 2.2 mmol), was dissolved in 20 mL of ethanol. Tin chloride dihydrate (2.97 g, 12.5 mmol) was added to the solution and the mixture was stirred and maintained at room temperature for 18 hours. HPLC (Eclipse XDB-C18, 4.6×250 mm, 5 micron, 1-99% CH3CN/H2O with 0.1% trifluoroacetic acid) indicated that all of the starting material (Rt=7.65 min) was consumed and a new single peak formed (Rt=5.9 min). The mixture was allowed to cool to room temperature before all volatiles were removed by rotary evaporation. The crude residue was dissolved in 100 mL of ethyl acetate and washed with 10% hydrochloric acid solution (3×30 mL). The organic layer was dried over Na2SO4, filtered and concentrated. The crude material was purified by silica gel chromatography (40 g Redisep column, silica, 40 um, 60 Å, 35 mL/min, A: hexanes, B: ethyl acetate, B: 0% to 85% over 40 min; detection at 214 nm) to give 7-(methyloxy)-6-(trifluoromethyl)-2H-1,4-benzoxazin-3(4H)-one (0.39 g, 1.6 mmol, 73%) as an off-white amorphous solid. MS (ES) m/e 248 [M+H]+.

Provenance & Evidence