Sodium Hydroxide → 7-Chloro-5-methyl-1H-pyrazolo[4,3-b]pyridine

Participants

Reaction Steps

The cyclized compound (12) (4.58 g, 30.7 mmol) in phosphorus oxychloride (30 mL) was heated at 110° C. for 30 minutes. The end of the reaction was checked by LC/MS (disappearance of 150, appearance of 168). After cooling down at room temperature, the reaction mixture was poured on ice and pH was adjusted with a 6N NaOH solution to pH=5. The solid was collected with filtration and the mother aqueous layer was extracted with ethyl acetate (3×250 ml). The above solid was dissolved in the combined organic phases, washed with a brine solution (1×250 ml) and dried with sodium sulfate, filtered and concentrated. The crude product was purified by running through a short silica gel chromatography column to give the desired product (13) as a pale yellow solid (4.50 g, 26.8 mmol, 87%). GC/MS: m/z=167 (100%);. LC/MS: [M+H]′=168.

Provenance & Evidence