Reacción #6525

Ecuación de reacción

pyrrole-2-carboxylic acid

o-aminophenol

boric acid

→

2-(pyrrol-2-yl)benzoxazole

Rendimiento 52.0%

Disolventes

ethyl acetate

xylene

Condiciones de reacción

Tratamiento posterior

1. 1
   Otro2-(Pyrrol-2-yl)benzoxazole was prepared
2. 2
   Temperaturawas heated
3. 3
   Temperaturaunder reflux for 3 days
4. 4
   Otrowhile removing water which
5. 5
   Otrowas generated from reaction
6. 6
   OtroThe cooled reaction mixture
7. 7
   Lavadowashed with 150 mL of 5% sodium hydroxide solution
8. 8
   SecadoThe separated organic layer was dried over anhydrous sodium sulfate
9. 9
   OtroThe resulting crude product was purified by column chromatography on silica gel with 20% hexane in chloroform as eluant

Procedimiento

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).

Fuente