Methyl 4-[(E)-2-(dimethylamino)vinyl]-5-nitropyridine-2-carboxylate → Methyl 1H-pyrrolo[2,3-c]pyridine-5-carboxylate

Temperature

25 °C

To a 500 mL Parr bottle was added methyl 4-[(E)-2-(dimethylamino)vinyl]-5-nitropyridine-2-carboxylate (18.9 g, 75.2 mmol) and anhydrous methanol (200 mL). The mixture was purged with nitrogen gas for 10 min. To this suspension was added Pd(10%)/C (1.90 g, 10 w/w %), and the suspension was degassed for 5 more minutes. The hydrogenation began with 43 psi H2 without heating. The reaction became exothermic as indicated by the rising temperature (about 2-3° C. per min) inside the Parr bottle (monitored by a thermal coupling thermometer). As the temperature inside of the reaction reached 45° C., the hydrogen gas flow into the Parr bottle was stopped, and the mixture was allowed to cool down to 25° C. for 30 min. The color of the liquid of the suspension changed from purple red to light green and then colorless in the first hour of the reduction, and about 30 psi H2 was consumed. The hydrogen pressure was brought to 50 psi, and the hydrogenation was continued at 50° C. for 20 h. There was no more hydrogen gas consumed in the last 20 h. After cooling the reaction mixture to 20° C., the solid mixture, which contained Pd(10%)/C and product, was filtered. The solid mixture was suspended in DMSO (200 mL), and the suspension was heated on a hot plate to 80° C. internal temperature with stirring for 10 min. The hot suspension was filtered and the Pd(10%)/C solid was washed with a small portion of DMSO (50 mL). The DMSO filtrate and washing were combined and poured into water (600 mL). Off white solid product precipitated out, and the suspension was stirred for 1 h before filtering, and lyophilizing. The title compound was obtained as an off-white solid product was obtained (11.3 g, >95% pure, 86% yield). 1H NMR (300 MHz, DMSO-d6) δ ppm 3.84 (s, 3H) 6.68 (d, J=2.8 Hz, 1H) 7.73 (d, J=3.0 Hz, 1H) 8.36 (s, 1H) 8.80 (s, 1H) 11.99 (s, 1H). LCMS: (APCI, M-H—)=175

1. customThe mixture was purged with nitrogen gas for 10 min
2. additionTo this suspension was added Pd(10%)/C (1.90 g, 10 w/w %)
3. customthe suspension was degassed for 5 more minutes
4. temperaturewithout heating
5. customreached 45° C.
6. customwas consumed
7. customconsumed in the last 20 h
8. temperatureAfter cooling the reaction mixture to 20° C.
9. filtrationwas filtered
10. temperaturethe suspension was heated on a hot plate to 80° C. internal temperature
11. filtrationThe hot suspension was filtered
12. washthe Pd(10%)/C solid was washed with a small portion of DMSO (50 mL)
13. washThe DMSO filtrate and washing
14. additionpoured into water (600 mL)
15. customOff white solid product precipitated out
16. stirringthe suspension was stirred for 1 h
17. filtrationbefore filtering

ORD record

ord-f3fe0bcc4562456b94487d1715ec706a

Source dataset

uspto-grants-2008_12

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07468375B2