Potassium Carbonate → tert-Butyl (2-chloro-benzoimidazol-1-yl)-acetate

HRID 2389464Notes

Reaction equation

HRID 2389464 reaction equation
C([O-])([O-])=O.[K+].[K+].[Cl:7][C:8]1[NH:9][C:10]2[CH:16]=[CH:15][CH:14]=[CH:13][C:11]=2[N:12]=1.Br[CH2:18][C:19]([O:21][C:22]([CH3:25])([CH3:24])[CH3:23])=[O:20]>CC(C)=O>[Cl:7][C:8]1[N:12]([CH2:18][C:19]([O:21][C:22]([CH3:25])([CH3:24])[CH3:23])=[O:20])[C:11]2[CH:13]=[CH:14][CH:15]=[CH:16][C:10]=2[N:9]=1

Participants

5

Reactant 3

HCID 11430Potassium CarbonateHCID 785722-ChlorobenzimidazoleHCID 79177tert-Butyl bromoacetate

Product 1

HCID 86224963tert-Butyl (2-chloro-benzoimidazol-1-yl)-acetateYield 88.5%

Reagents, catalysts & solvents 1

HCID 180AcetoneSolvent

Procedure

In a round bottomed flask are added K2CO3 (9.34 g, 67.7 mmol), 2-chlorobenzimidazole (5.16 g, 33.8 mmol) and tert-butyl bromoacetate (6.6 g, 5 ml, 33.8 mmol) in acetone (100 ml). The resulting suspension is refluxed for 1 h. The crude mixture is filtered through a filter paper and water (100 ml) is added. The resulting aqueous phase is extracted three times with Et2O. The combined organic phases are washed with brine and dried over MgSO4. The solvent is evaporated under reduced pressure yielding the title compound (7.98 g) in 88% as a white powder: tR=2.20 min (LC-2), ESI-MS (pos.): m/z 267.2 [M+H]+; 1H-NMR (CDCl3): δ (ppm) 1.48 (s, 9H, tBu), 4.92 (s, 2H, CH2CO2), 7.24-7.40 (m, 3Harom), 7.76-7.80 (m, 1Harom). Intermediate 2-IIa and 2-IIb tert-Butyl (2-chloro-5-nitro-benzoimidazol-1-yl)-acetate and its 6-nitro regioisomer are prepared according to the same procedure (yield 93%): tR=6.68 min (LC-1), ESI-MS (pos.): m/z 312.08 [M+H]+, 310.28 [M−H]+; 1H-NMR (CDCl3): δ (ppm) 1.50 (s, 9H, tBu), 1.52 (s, 9H, tBu), 5.04 and 5.06 (s, 2H, CH2CO2), 7.38 (d, 1Harom), 7.86 (d, 1 Harom), 8.32-8.40 (m, 3Harom), 8.96 (m, 1Harom).

Workup

  1. temperatureThe resulting suspension is refluxed for 1 h
  2. filtrationThe crude mixture is filtered through a filter paper and water (100 ml)
  3. additionis added
  4. extractionThe resulting aqueous phase is extracted three times with Et2O
  5. washThe combined organic phases are washed with brine
  6. dry with materialdried over MgSO4
  7. customThe solvent is evaporated under reduced pressure

Sources & evidence

ORD record
ord-dd1e2e6536464736aebcdcbd21d2534f
Source dataset
uspto-grants-2012_09
Patent number
US08273740B2

Reaction notes

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