Reaction #985273

Reaction equation

POCl3

sodium acetate

POCl3

Dimethylformamide

POCl3

N-ethylcarbazole

DMF

→

N-ethyl-3,6-diformylcarbazole

Yield 46.0%

Solvents

water

Conditions

Workup

1. 1
   Otherequipped with a mechanical stirrer
2. 2
   TemperatureThe contents were cooled in a salt/ice bath
3. 3
   Otherreached 0° C.
4. 4
   Otherto rise above 5° C
5. 5
   TemperatureAfter the flask warmed to room temperature
6. 6
   Temperaturethe flask was heated to 90° C. for 24 hours
7. 7
   TemperatureNext, the reaction mixture was cooled to room temperature
8. 8
   workup.ADDITIONthe reaction mixture was added slowly to a cooled 4.5 liter beaker
9. 9
   workup.ADDITIONcontaining a solution
10. 10
    TemperatureThe beaker was cooled in an ice bath
11. 11
    OtherThe brownish solid obtained
12. 12
    Filtrationwas filtered
13. 13
    Washwashed repeatedly with water
14. 14
    WashAfter washing
15. 15
    Otherthe resulting product was recrystallized once from toluene using activated charcoal
16. 16
    Otherdried under vacuum in an oven
17. 17
    Temperatureheated at 70° C. for 6 hours

Procedure

Dimethylformamide (DMF, 271 ml, 3.5 mol, obtained from Aldrich, Milwaukee, Wis.) was added to a 1-liter 3-neck round-bottomed flask equipped with a mechanical stirrer, a thermometer, and a dropping funnel. The contents were cooled in a salt/ice bath. When the temperature inside the flask reached 0° C., 326 ml of POCl3 (3.5 mol) was slowly added. During the addition of POCl3, the temperature inside the flask was not allowed to rise above 5° C. After the addition of POCl3 was completed, the reaction mixture was allowed to warm to room temperature. After the flask warmed to room temperature, N-ethylcarbazole (93 g, obtained from Aldrich) in 70 ml of DMF was added, and then the flask was heated to 90° C. for 24 hours using a heating mantle. Next, the reaction mixture was cooled to room temperature and the reaction mixture was added slowly to a cooled 4.5 liter beaker containing a solution comprising 820 g of sodium acetate dissolved in 2 liters of water. The beaker was cooled in an ice bath and stirred for 3 hours. The brownish solid obtained was filtered and washed repeatedly with water, followed by a small amount of ethanol (50 ml). After washing, the resulting product was recrystallized once from toluene using activated charcoal and dried under vacuum in an oven heated at 70° C. for 6 hours to obtain 55 g (46% yield) of N-ethyl-3,6-diformylcarbazole. The 1H-NMR spectrum (250 MHz) of the product in CDCl3 was characterized by the following chemical shifts (δ, ppm): 10.12 (s, 2H); 8.63 (s, 2H); 8.07 (d, 2H); 7.53 (d, 2H); 4.45 (m, 2H); 1.53 (t, 3H).

Source