2-Hydroxy benzimidazole → 2-Chlorobenzimidazole

HRID 1446871Notes

Reaction equation

HRID 1446871 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.P(Cl)(Cl)([Cl:13])=O>>[Cl:13][C:2]1[NH:3][C:4]2[CH:9]=[CH:8][CH:7]=[CH:6][C:5]=2[N:1]=1

Participants

3

Reactant 2

HCID 119852-Hydroxy benzimidazoleHCID 24813Phosphorus oxychloride

Product 1

HCID 785722-Chlorobenzimidazole

Procedure

Benzimidazolin-2-one (13.0 g) was added to phosphoryl chloride and the mixture was heated under reflux for a period of 3.5 hours. The excess phosphoryl chloride was removed by distillation and the residue was treated with water. The acidic solution was cooled, filtered and made basic by the addition of dilute ammonium hydroxide. The solid was collected and recrystallised from aqueous ethanol to give 2-chlorobenzimidazole (11.5 g) as colourless needles, mp 214° C.

Workup

  1. temperaturethe mixture was heated
  2. temperatureunder reflux for a period of 3.5 hours
  3. customThe excess phosphoryl chloride was removed by distillation
  4. additionthe residue was treated with water
  5. temperatureThe acidic solution was cooled
  6. filtrationfiltered
  7. additionmade basic by the addition of dilute ammonium hydroxide
  8. customThe solid was collected
  9. customrecrystallised from aqueous ethanol

Sources & evidence

ORD record
ord-b37fbe4ac6474a5a917e6275a0c0a61a
Source dataset
uspto-grants-1982_02
Patent number
US04314065

Reaction notes

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