Reaction #6524

Reaction equation

sodium acetate

5-(pyrrol-2-yl)oxazole

dimethylformamide

phosphorus oxychloride

→

5-(5-formylpyrrol-2-yl)oxazole

Yield 80.0%

Solvents

chloroform

1,2-dichloroethane

Conditions

Workup

1. 1
   workup.STIRRINGThe mixture was stirred 20 minutes
2. 2
   Temperaturewhile cooling in an ice bath
3. 3
   TemperatureThe reaction mixture was then heated
4. 4
   Temperatureunder reflux for 20 minutes
5. 5
   TemperatureAfter heating
6. 6
   Temperatureunder reflux for 20 minutes
7. 7
   Temperaturethe mixture was cooled to room temperature
8. 8
   Otherthe organic layer separated
9. 9
   Washwashed with aqueous sodium carbonate
10. 10
    Dryingdried over anhydrous sodium sulfate
11. 11
    Otherevaporation of the solvent at reduced pressure
12. 12
    Otherthe crude product was purified by column chromatography with chloroform elution

Procedure

To an ice cooled 1 mL dimethylformamide was added 0.82 g (5.4 mmol) of phosphorus oxychloride while stirring under a nitrogen atmosphere. The mixture was stirred 20 minutes and then was added a solution of 0.60 g (4.5 mmol) of 5-(pyrrol-2-yl)oxazole in 15 mL of 1,2-dichloroethane while cooling in an ice bath. The reaction mixture was then heated under reflux for 20 minutes. After cooling to room temperature, 50 mL of chloroform was added followed by 60 mL of saturated aqueous sodium acetate. After heating under reflux for 20 minutes, the mixture was cooled to room temperature and the organic layer separated, washed with aqueous sodium carbonate and dried over anhydrous sodium sulfate. Following evaporation of the solvent at reduced pressure, the crude product was purified by column chromatography with chloroform elution to give 0.58 g (80%) of 5-(5-formylpyrrol-2-yl)oxazole as a white solid, m.p. 152°-153° C.; 1H-NMR (Acetone-d6) δ 6.68 (d, 1H, ArH), 7.09 (d, 1H, ArH), 7.61 (S, 1H, ArH), 8,22 (s, 1H, ArH), 9.57 (s, 1H, CHO).

Source