Hydrochloric Acid → 2-Hydroxy benzimidazole

HRID 543885Notes

Reaction equation

HRID 543885 reaction equation
[NH:1]1[C:5]2[CH:6]=[CH:7][CH:8]=[CH:9][C:4]=2[NH:3][C:2]1=[O:10].[ClH:11]>P(Cl)(Cl)(Cl)=O>[NH:1]1[C:5]2[CH:6]=[CH:7][CH:8]=[CH:9][C:4]=2[NH:3][C:2]1=[O:10].[Cl:11][C:2]1[NH:3][C:4]2[CH:9]=[CH:8][CH:7]=[CH:6][C:5]=2[N:1]=1

Participants

5

Reactant 2

HCID 313Hydrochloric AcidHCID 119852-Hydroxy benzimidazole

Product 2

HCID 119852-Hydroxy benzimidazoleHCID 785722-Chlorobenzimidazole

Reagents, catalysts & solvents 1

HCID 24813Phosphorus oxychlorideSolvent

Procedure

Following the procedure of Harrison et al., J.Chem.Soc., 1963, 2930-2937, 15 g benzimidazolin-2-one is boiled under reflux for 31/2 hours with 150 ml phosphoryl chloride, dry hydrogen chloride being passed through the refluxing mixture for the last three hours of the reaction. The excess phosphoryl chloride is removed at about 40 mm and the residue treated with about 40 ml of ice water. The cold acid solution is filtered, and the insoluble unreacted benzimidolin-2-one is washed with dilute hydrochloric acid, then with water. The filtrate and washings are made just alkaline, as determined by a litamus test, by the addition of dilute ammonia solution. After thorough cooling, crude 2-chlorobenzimidazole is collected, washed with water and dried. The reaction sequence yields 0.5 g of unreacted benzimidazolin-2-one and 15.6 g of title compound which has a m.p. of 180° C. (softens, bubbles, then resolidifies).

Workup

  1. custompassed through the refluxing mixture for the last three hours of the reaction
  2. customThe excess phosphoryl chloride is removed at about 40 mm
  3. additionthe residue treated with about 40 ml of ice water
  4. filtrationThe cold acid solution is filtered
  5. washthe insoluble unreacted benzimidolin-2-one is washed with dilute hydrochloric acid
  6. additionas determined by a litamus test, by the addition of dilute ammonia solution
  7. customAfter thorough cooling, crude 2-chlorobenzimidazole is collected
  8. washwashed with water
  9. customdried

Sources & evidence

ORD record
ord-d63b91b9c55b40548a5c38ef39ec876c
Source dataset
uspto-grants-1984_05
Patent number
US04447611

Reaction notes

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