Cinchomeronic acid → 1H,3H-furo(3,4-c)pyridine-1,3-dione

Temperatur

70 °C

Under nitrogen atmosphere a suspension of a 97% pure 3,4-pyridine dicarboxylic acid (152 g, 0.88 mol) in acetic anhydride (450 mL) was heated to reflux and a complete solution was obtained. Once refluxing temperature was reached, solvent was removed by distillation at atmospheric pressure (about 400 ml were collected) over a period of about 1 hour. Vapors temperature was observed to increase from about 132° C. to 140° C. and distillation was stopped when internal temperature reached 150°-155° C. The reaction mixture was cooled to 70° C. and tert-BuOMe (450 mL) was added dropwise under stirring. A dark grey solid precipitated at about 40° C. while temperature was spontaneously let reach 20°-25° C. The suspension was further cooled to 0°-5° C. and stirred for two hours. Under nitrogen blanket the dark grey precipitate was collected by filtration, washed with tert-BuOMe (100 mL) and dried under vacuum (20 torr; 30° C.; 2 h) to yield 3,4-pyridine dicarboxylic acid anhydride (100 g; yield 76%) which was directly used in the next step.

1. temperaturewas heated
2. temperatureto reflux
3. customa complete solution was obtained
4. temperatureOnce refluxing temperature
5. customsolvent was removed by distillation at atmospheric pressure (about 400 ml were collected) over a period of about 1 hour
6. temperatureto increase from about 132° C. to 140° C.
7. distillationdistillation
8. customreached 150°-155° C
9. additiontert-BuOMe (450 mL) was added dropwise
10. customA dark grey solid precipitated at about 40° C. while temperature
11. customwas spontaneously let reach 20°-25° C
12. temperatureThe suspension was further cooled to 0°-5° C.
13. stirringstirred for two hours
14. filtrationUnder nitrogen blanket the dark grey precipitate was collected by filtration
15. washwashed with tert-BuOMe (100 mL)
16. customdried under vacuum (20 torr; 30° C.; 2 h)

ORD-Eintrag

ord-9f8de0e4f86443169ec40226b5714163

Quelldatensatz

uspto-grants-1998_02

DOI

10.6084/m9.figshare.5104873.v1

Patentnummer

US05717099