Sodium Carbonate → tert-Butyl 1-phenyl-1,4,6,7-tetrahydro-5H-pyrazolo[4,3-c]pyridine-5-carboxylate

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Reaction Steps

Tert-butyl 3-((dimethylamino)methylene)-4-oxopiperidine-1-carboxylate (Step A, 2.1 g, 8.3 mmol) was dissolved in 100 mL methanol, and water (50 mL) was added followed by the addition of sodium carbonate (0.53 g, 5.0 mmol) and phenyl hydrazine hydrochloride (1.43 g, 9.9 mmol). Finally, acetic acid (1 mL) was added and the resulting mixture was stirred at rt for 1 h. The mixture was made basic by adding saturated aq. sodium bicarbonate (ca. 20 mL) and the methanol was removed on a rotary evaporator. The resulting mixture was extracted with methylene chloride (3×40 mL) and the combined extracts were dried over anhyd. sodium sulfate, filtered, and concentrated to afford the crude product. Purification by flash chromatography on silica gel using 20% ethyl acetate in hexanes as the eluant afforded fractions containing the desired product. Concentration of the combined fractions afforded the desired product b as a yellow oil (1.63 g, 66%). 1H NMR (400 MHz, d3-MeOD): δ 7.73 (s, 1H), 7.60-7.47 (m, 5H), 4.37 (s, 2H), 3.57 (t, J=6.1 Hz, 2H), 3.17 (t, J=6.0 Hz, 2H).

Provenance & Evidence