2-Aminophenol → 2-(2H-Pyrrol-2-ylidene)-2,3-dihydro-1,3-benzoxazole

HRID 6429

Reaction equation

HRID 6429 reaction equation
[NH:1]1[CH:5]=[CH:4][CH:3]=[C:2]1[C:6]([OH:8])=O.[NH2:9][C:10]1[CH:15]=[CH:14][CH:13]=[CH:12][C:11]=1O.B(O)(O)O>C1(C)C(C)=CC=CC=1.C(OCC)(=O)C>[NH:1]1[CH:5]=[CH:4][CH:3]=[C:2]1[C:6]1[O:8][C:11]2[CH:12]=[CH:13][CH:14]=[CH:15][C:10]=2[N:9]=1

Participants

6

Reactant 3

HCID 58012-AminophenolHCID 7628Boric AcidHCID 12473Pyrrole-2-Carboxylic Acid

Product 1

HCID 1356254822-(2H-Pyrrol-2-ylidene)-2,3-dihydro-1,3-benzoxazoleYield 52%

Reagents, catalysts & solvents 2

HCID 7237O-XyleneSolventHCID 8857Ethyl AcetateSolvent

Procedure

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).

Workup

  1. custom2-(Pyrrol-2-yl)benzoxazole was prepared
  2. temperaturewas heated
  3. temperatureunder reflux for 3 days
  4. customwhile removing water which
  5. customwas generated from reaction
  6. customThe cooled reaction mixture
  7. washwashed with 150 mL of 5% sodium hydroxide solution
  8. dry with materialThe separated organic layer was dried over anhydrous sodium sulfate
  9. customThe resulting crude product was purified by column chromatography on silica gel with 20% hexane in chloroform as eluant

Sources & evidence

ORD record
ord-2288569fc3ee4fffb9e3876b2052db84
Source dataset
uspto-grants-1993_09
Patent number
US05248782

Linked notes

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