Réaction #6525

Équation de réaction

pyrrole-2-carboxylic acid

o-aminophenol

boric acid

→

2-(pyrrol-2-yl)benzoxazole

Rendement 52.0%

Solvants

ethyl acetate

xylene

Conditions de réaction

Traitement

1. 1
   Autre2-(Pyrrol-2-yl)benzoxazole was prepared
2. 2
   Températurewas heated
3. 3
   Températureunder reflux for 3 days
4. 4
   Autrewhile removing water which
5. 5
   Autrewas generated from reaction
6. 6
   AutreThe cooled reaction mixture
7. 7
   Lavagewashed with 150 mL of 5% sodium hydroxide solution
8. 8
   SéchageThe separated organic layer was dried over anhydrous sodium sulfate
9. 9
   AutreThe resulting crude product was purified by column chromatography on silica gel with 20% hexane in chloroform as eluant

Mode opératoire

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).

Source