Реакция #80681

Уравнение реакции

3,4-pyridine dicarboxylic acid

→

3,4-pyridine dicarboxylic acid anhydride

Выход 76.2%

Растворители

acetic anhydride

Условия реакции

Обработка

1. 1
   Температураwas heated
2. 2
   Температураto reflux
3. 3
   Другоеa complete solution was obtained
4. 4
   ТемператураOnce refluxing temperature
5. 5
   Другоеsolvent was removed by distillation at atmospheric pressure (about 400 mL were collected) over a period of about 1 hour
6. 6
   Температураto increase from about 132° C. to 140° C.
7. 7
   workup.DISTILLATIONdistillation
8. 8
   Другоеreached 150°-155° C
9. 9
   workup.ADDITIONtert-BuOMe (450 mL) was added dropwise
10. 10
    ДругоеA dark grey solid precipitated at about 40° C. while temperature
11. 11
    Другоеwas spontaneously let reach 20°-25° C
12. 12
    ТемператураThe suspension was further cooled to 0°-5° C.
13. 13
    workup.STIRRINGstirred for two hours
14. 14
    ФильтрацияUnder nitrogen blanket the dark grey precipitate was collected by filtration
15. 15
    Промывкаwashed with tert-BuOMe (100 mL)
16. 16
    Другоеdried under vacuum (20 torr; 30° C.; 2 h)

Методика

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.

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