Tribromo-l-vinylimidazole

2-Dibromoethane (30 ml, 65.4 g,. 348 mmol) and triethylamine (30 ml) are added to a stirred solution of 2,4,5-tribromoimidazole (lO.Og, 32.8 mmol) in triethylamine (20ml) at ambient temperature, and the resulting mixture is heated under reflux until all of the starting material has been consumed (1 h), as shown by TLC analysis (at this stage the products are 1-bromoethyl- and 

1-vinyl-2,4,5-tribromoimidazoles). Aqueous sodium carbonate (10%, 30 ml) and tctrabutylammonium bromide (2.6 g, 8.06 mmol) are added to the mixture, which is refluxed (2h) when TLC shows the presence of only one product. Water (200 ml) is added to the cooled mixture, and the product is extracted with ether (4 x 30 ml). The combined extracts arc washed with 10% aqueous HCl (2 X 50 ml) and dried (MgS04), and the solvents are removed under reduced pressure. Distillation of the residue using a Kugelrohr apparatus gives the product as a white solid (8.32g, 77%), bo.os 108-110°C, m.p. 31-32°C, Vmax 1642 cm-.  

Ozone is bubbled through a stirred solution of 4-bromo-l-vinylimidazolc-5-carbonitrile (0.5 g, 2.53 mmol) in methanol (30 ml) at —78°C until TLC analysis shows complete reaction (30 min). Dimethyl sulfide (0.2 ml, 0.17 g, 2.72 mmol) is added, and the mixture is allowed to waum up to room temperature and stirred (1 h). Distillation of the solvent under reduced pressure gives the product (0.35 g, 80%) as a white solid after recrystallization from aqueous ethanol, m.p. 142-144°C. 

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