Reaktion #6525

Reaktionsgleichung

pyrrole-2-carboxylic acid

o-aminophenol

boric acid

→

2-(pyrrol-2-yl)benzoxazole

Ausbeute 52.0%

Lösungsmittel

ethyl acetate

xylene

Reaktionsbedingungen

Aufarbeitung

1. 1
   Sonstige2-(Pyrrol-2-yl)benzoxazole was prepared
2. 2
   Temperaturwas heated
3. 3
   Temperaturunder reflux for 3 days
4. 4
   Sonstigewhile removing water which
5. 5
   Sonstigewas generated from reaction
6. 6
   SonstigeThe cooled reaction mixture
7. 7
   Waschenwashed with 150 mL of 5% sodium hydroxide solution
8. 8
   TrocknenThe separated organic layer was dried over anhydrous sodium sulfate
9. 9
   SonstigeThe resulting crude product was purified by column chromatography on silica gel with 20% hexane in chloroform as eluant

Vorschrift

2-(Pyrrol-2-yl)benzoxazole was prepared as follows: A mixture of 5.55 g (0.05 mol) of pyrrole-2-carboxylic acid and 5.46 g (0.05 mol) of o-aminophenol and 3.09 g (0.05 mol) boric acid in 50 mL of xylene was heated under reflux for 3 days while removing water which was generated from reaction using a Dean-Stark trap. The cooled reaction mixture was diluted with 100 mL of ethyl acetate, washed with 150 mL of 5% sodium hydroxide solution and then with 150 mL of water. The separated organic layer was dried over anhydrous sodium sulfate. The resulting crude product was purified by column chromatography on silica gel with 20% hexane in chloroform as eluant. The desired product, 2-(pyrrol-2-yl)benzoxazole (4.75 g, 52%), was obtained as a white solid. m.p. 149°-150° C.; 1H NMR (CDCl3) δ6.38-6.40 (m, 1H, ArH), 7.05-7.06 (m, 1H, ArH), 7.11-7.13 (m, 1H, ArH), 7.29-7.36 (m, 2H, 2xArH), 7.53-7.56 (m, 1H, ArH), 7.65-7.69 (m, 1H, ArH), 10.9 (bs, 1H, NH).

Quelle