Acetic Acid → [7-(2-Chloro-4-methoxyphenyl)-2-ethylpyrazolo[1,5-a]pyridin-3-yl]amine

Participants

Reaction Conditions

Reaction Steps

7-(2-Chloro-4-methoxyphenyl)-2-ethyl-3-nitropyrazolo[1,5-a]pyridine (5 mg) was suspended in ethanol (2 mL), and then water (1 mL), acetic acid (0.5 mL) and zinc powder (10 mg) were added and the mixture was heated and stirred at 80° C. for 30 minutes. The reaction mixture was filtered, water was added to the filtrate, extraction was performed with ethyl acetate and the extract was washed with saturated aqueous sodium hydrogencarbonate and brine. After drying over anhydrous magnesium sulfate and filtration, the solvent was concentrated under reduced pressure to obtain [7-(2-chloro-4-methoxyphenyl)-2-ethylpyrazolo[1,5-a]pyridin-3-yl]amine as crude crystals. These were dissolved in tetrahydrofuran (1 mL) without further purification, and after adding propionaldehyde (0.015 mL) and 3 M aqueous sulfuric acid (0.071 mL), sodium borohydride (5.4 mg) was added in five portions while vigorously stirring on ice, and stirring was continued for 30 minutes. Water was added to the reaction mixture, extraction was performed with diethyl ether and the extract was washed with saturated sodium hydrogencarbonate and brine. After drying over anhydrous magnesium sulfate and filtration, the solvent was concentrated under reduced pressure and the residue was purified by preparative TLC [n-hexane:ethyl acetate (5:1), Rf=0.5] to obtain the title compound (6 mg) as a light yellow oil.

Provenance & Evidence