Hydrogen Bromide → 2-bromo-5,6-dichloro-1H-benzimidazole

HRID 727000

Reaction equation

HRID 727000 reaction equation
N[C:2]1[NH:3][C:4]2[CH:10]=[C:9]([Cl:11])[C:8]([Cl:12])=[CH:7][C:5]=2[N:6]=1.[BrH:13].N([O-])=O.[Na+]>O>[Br:13][C:2]1[NH:3][C:4]2[CH:10]=[C:9]([Cl:11])[C:8]([Cl:12])=[CH:7][C:5]=2[N:6]=1

Participants

5

Reactant 3

HCID 260Hydrogen BromideHCID 4660162-Amino-5,6-dichlorobenzimidazoleHCID 23668193Sodium Nitrite

Product 1

HCID 4660172-bromo-5,6-dichloro-1H-benzimidazoleYield 26%

Reagents, catalysts & solvents 1

HCID 962WaterSolvent

Procedure

2-Amino-5,6-dichlorobenzimidazole (3 g, 16 mmole) was suspended in 150 ml of water and brought into solution with 2 ml of HBr. Sodium nitrite (3.3 g, 55 mmole) was then added and the mixture was stirred at room temperature for 1 hr. Excess CuBr2 was then added and the mixture was heated on a steam beth for 1 hr. The aqueous solution was extracted with ethyl acetate (3×100 ml), dried with MgSO4, concentrated, and crystallized from ethyl ether to give 1.13 g (26%) of 2-bromo-5,6-dichlorobenzimidazole (7). 1H NMR DMSO-d6) δ7.81 ppm (s, 2H), 13.62 (s, 1H). GC/MS: m/e 266, 185, 158, 150, 133, 124, 107, 97, 88, 73, 62, 52, 37.

Workup

  1. temperaturethe mixture was heated on a steam beth for 1 hr
  2. extractionThe aqueous solution was extracted with ethyl acetate (3×100 ml)
  3. dry with materialdried with MgSO4
  4. concentrationconcentrated
  5. customcrystallized from ethyl ether

Sources & evidence

ORD record
ord-5e74e0efb9d645a38c7d5810ad44e219
Source dataset
uspto-grants-1998_01
Patent number
US05712255

Linked notes

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