Sodium Hydroxide → 6-(2,4-Difluorophenyl)imidazo[2,1-b]oxazole

Participants

Reaction Conditions

Reaction Steps

Polyphosphoric acid (124.4 g) was charged to a flask and heated to about 80° C. 1-(2,4-Difluorophenyl)-2-(2-iminooxazol-3(2H)-yl)ethanone hydrobromide salt (19.8 g, 62.0 mmol, Preparation #B.1 intermediate) was transferred to the flask in approximately 3 g portions over about 2 h. The thick solution was mixed and heated at about 80-90° C. for about 22 h. The reaction mixture was slowly transferred to a flask containing water (150 mL) and 30% aqueous NaOH (150 mL) that had been cooled to about 5-10° C. The pH of the resulting slurry was adjusted to about 5.4 by addition of 30% aqueous NaOH and the product was isolated by filtration. The wet cake was rinsed with warm water (3×150 mL) and dried under vacuum to give the title compound (9.5 g, 69%): MS m/z 221.1 (M+H)+ FIA (APCI)

Provenance & Evidence