Methyl 1H-pyrrolo[2,3-c]pyridine-5-carboxylate

868551-31-9

147071-00-9

Methyl 4-[(E)-2-(dimethylamino)vinyl]-5-nitropyridine-2-carboxylate (75.2 mmol) and anhydrous methanol (200 mL) were added to a 500 mL Parr reactor. The mixture was purged with nitrogen for 10 min. Pd/C (10 wt%, 1.90 g) was added to the suspension and degassed again for 5 min. The hydrogenation reaction was initiated at a H2 pressure of 43 psi without incoming heat. The reaction was exothermic and the temperature in the Parr reactor increased at a rate of about 2-3°C/min as monitored by a thermally coupled thermometer. When the reaction temperature reached 45°C, the passage of hydrogen was stopped and the mixture was cooled to 25°C for 30 minutes. During the first hour of reduction, the color of the suspension changed from purplish red to light green and eventually colorless, at which time approximately 30 psi of H2 was consumed.Subsequently, the hydrogen pressure was adjusted to 50 psi and the hydrogenation was continued for 20 hours at 50° C. The reaction temperature was reduced to 45° C. The reaction temperature was reduced to 25°C/min. No further hydrogen consumption was observed during this 20 hour period. Upon completion of the reaction, the mixture was cooled to 20°C and filtered to remove the Pd/C catalyst. The solid residue was suspended in DMSO (200 mL), heated to 80°C and stirred for 10 min. The suspension was filtered while hot and the Pd/C solids were washed with a small amount of DMSO (50 mL). The DMSO filtrate and washings were combined and poured into water (600 mL) and stirred for 1 hour to precipitate the off-white solid product. The product was collected by filtration and lyophilized to afford methyl 1H-pyrrolo[2,3-c]pyridine-5-carboxylate (11.3 g, purity >95%, yield 86%). The structure of the product was confirmed by 1H NMR (300 MHz, DMSO-d6) and LCMS (APCI, M-H- = 175).