Trifluoroacetic acid → 2-Benzoxazolinone, 5-methoxy-

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Reaction Conditions

Reaction Steps

2-amino-4-(methyloxy)phenol, HCl salt (1.0 g, 5.7 mmol) was dissolved in 20 mL of anhydrous tetrahydrofuran under argon. The mixture was heated to reflux (70° C.) and then 1,1′-carbonyldiimidazole (1.2 g, 7.4 mmol) was slowly added in small portions over a one hour period. After the addition was complete, the reaction continued to reflux for another 2.5 hours, before it was determined to be complete by LCMS (two Aquasil C18, 20×1 mm columns were run in sequence, 4 minutes at 0.1 mL/min, 1-99% CH3CN/H2O with 0.018% trifluoroacetic acid, ES) Rt=1.0 min and m/e 166 [M+1]+. 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 ether and washed with water (3×30 mL) and brine (3×30 mL). The organic layer was dried over Na2SO4, filtered and concentrated to give 5-(methyloxy)-1,3-benzoxazol-2(3H)-one (0.78 g, 4.7 mmol, 82%) as an orange amorphous solid. MS (ES) m/e 166 [M+H]+.

Provenance & Evidence