Acetic Anhydride → 7-(2,4-dichloro-phenyl)-1H-pyrazolo[3,4-c]pyridine

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Reaction Steps

To a mixture of N-[2-(2,4-dichloro-phenyl)-4-methyl-pyridin-3-yl]-acetamide (30; 0.787 g, 2.67 mmol), 30 mL of benzene, acetic anhydride (0.780 mL, 8.27 mmol), and potassium acetate (0.330 g, 3.36 mmol) at 78° C. was added isoamyl nitrite (0.572 mL, 4.27 mmol), and the yellow mixture was stirred for 22 h. After cooling, the mixture was filtered and concentrated to an orange oil. To the oil was added 21 mL of ethanol, 7 mL of water, and lithium hydroxide monohydrate (0.339 g, 8.80 mmol). The orange mixture was stirred for 3 h, then concentrated to remove ethanol. The orange residue was partitioned between 50 mL of diethyl ether and 50 mL of a 10% aqueous NaOH solution, and the aqueous layer was extracted with 50 mL of diethyl ether. The combined organic layers were washed with 100 mL of a saturated aqueous NaCl solution, dried over MgSO4, filtered, loaded onto silica gel and concentrated. Column chromatography (0→20% EtOAc/hexanes) afforded of 7-(2,4-dichloro-phenyl)-1H-pyrazolo[3,4-c]pyridine (31; 0.484 g; 67%) as a foamy pale yellow solid.

Provenance & Evidence