Hydrochloric Acid → 2-ethyl-1-(2-methylpropyl)-2H-pyrazolo[3,4-c][1,8]naphthyridin-4-amine

Participants

Reaction Conditions

Reaction Steps

Hydrochloric acid (15 mL of 1M) was added to a solution of 2-tert-butoxycarbonylamino-3-pyridylboronic acid (3.31 g, 13.9 mmol), prepared as described in Parts A and B of Example 15, in 1-propanol (15 mL), and the resulting mixture was heated at 80° C. for one hour and allowed to cool to ambient temperature. Solid sodium carbonate (2.69 g, 25.4 mmol) was added with stirring followed by a solution of 4-bromo-1-ethyl-5-(2-methylpropyl)-1H-pyrazole-3-carbonitrile (1.78 g, 6.95 mmol), prepared as described in Example 2, in 1-propanol (4 mL). Triphenylphosphine (109 mg, 0.42 mmol) was added, and the reaction was evacuated and backfilled with nitrogen three times and stirred for five minutes. A solution of palladium (II) acetate (31 mg, 0.14 mmol) in warm toluene (0.5 mL) was added. The reaction was twice evacuated and backfilled with nitrogen and then heated at 100° C. overnight. An analysis by HPLC indicated the reaction was incomplete, and additional triphenylphosphine (109 mg, 0.42 mmol) and palladium (II) acetate (31 mg, 0.14 mmol) were added. The reaction was twice evacuated and backfilled with nitrogen at heated at reflux for three days. The 1-propanol was removed under reduced pressure, and the residue was dissolved in chloroform (100 mL). The resulting solution was washed with water, dried over magnesium sulfate, filtered, and concentrated under reduced pressure. The crude product was purified by chromatography on a HORIZON HPFC system as described in Example 15. The resulting solid (200 mg) was recrystallized from acetonitrile (20 mL) after hot filtration, isolated by filtration, washed with cold acetonitrile, and dried overnight in a vacuum oven at 60° C. to provide 0.17 g of 2-ethyl-1-(2-methylpropyl)-2H-pyrazolo[3,4-c][1,8]naphthyridin-4-amine as off-white needles, mp 273-276° C.

Provenance & Evidence