Water → 5-Chloro-2-(4-methoxyphenyl)pyrazolo[1,5-a]pyridine

Participants

Reaction Conditions

Reaction Steps

To a solution of 2-(4-chloro-2-pyridinyl)-1-(4-methoxyphenyl)ethanone oxime (11.8 g, 42.6 mmol) in 1,2-dimethoxyethane (200 mL) at 0° C. was added trifluoroacetic anhydride (6.3 mL, 44.8 mmol), keeping the temperature below 10° C. during the addition. After the addition was complete, the reaction was warmed to 15° C. The solution was then cooled to 4° C. and a solution of triethylamine (12.5 mL, 89.5 mmol) in 1,2-dimethoxyethane (15 mL) was added over a period of 0.5 hours. The mixture was allowed to warm to room temperature and was stirred at room temperature for 5 hours. To this mixture was added iron(II)chloride (0.11 g, 0.85 mmol) and the reaction was heated at 75° C. for 15 hours. The reaction mixture was poured into water (300 mL). The resulting suspension was extracted with ethyl acetate. The organic phase was dried (magnesium sulfate), filtered and concentrated to a solid. This solid was recrystallized from methanol to give 5-chloro-2-(4-methoxyphenyl)pyrazolo[1,5-α]pyridine (6.64 g, 60%) as white needles. 1H NMR (CDCl3): δ 8.35 (d, 1H), 7.86 (d, 2H), 7.46 (d, 1H), 6.97 (d, 2H), 6.67 (d, 1H), 6.65 (s, 1H), 3.85 (s, 3H); MS m/z 259 (M+1).

Provenance & Evidence