Sulfuric Acid → 2,6-Difluoro-N-{1-[(5-hydroxy-2-methylphenyl)methyl]-1H-pyrazol-3-yl}benzamide

Participants

Reaction Conditions

Reaction Steps

To N-{1-[(5-amino-2-methylphenyl)methyl]-1H-pyrazol-3-yl}-2,6-difluorobenzamide (for a preparation see Intermediate 48) (0.312 g, 0.911 mmol) in an ice-water bath was added sulphuric acid specific gravity 1.84 (3 ml, 56.3 mmol). To the stirred suspension was slowly added water (5 ml). To the slight suspension was added a solution of sodium nitrite (0.132 g, 1.91 mmol, Aldrich) in water (1 ml). The solution was maintained at 0-5° C. for 20 min. To the solution was added urea (0.350 g, 5.83 mmol, Aldrich) and then copper (II) sulphate (50 mg, 0.313 mmol, Fluka). The mixture was heated to 90° C. for 30 min. The mixture was allowed to stand at ambient temperature overnight. The mixture was diluted with water (100 ml) and then ethyl acetate (50 ml). The phases were separated and the aqueous phase extracted with ethyl acetate (25 ml). The combined organic extracts were concentrated in vacuo to leave a brown gum (0.3 g). The residue was loaded in dichloromethane and purified on silica 50 g using 0-100% ethyl acetate-cyclohexane. The appropriate fractions were combined and evaporated in vacuo to give the title compound as a yellow foam (206 mg); LCMS (System 4) MH+=344, tRET=2.36 min.

Provenance & Evidence