General procedure for the synthesis of 2-bromo-4-methyl-1H-imidazole from 2,5-dibromo-4-methylimidazole: [Example 6]; At room temperature, 23.9 g (100.0 mmol) of 2,5-dibromo-4-methylimidazole, 29.4 g (300.0 mmol) of cyclohexanone, and 23.9 g (259.4 mmol) of toluene were mixed, and during stirring, slow addition of 22.5 g (150.0 mmol) of sodium iodide to prepare the reaction solution. The reaction solution was stirred at 105 °C for 12 h under nitrogen protection, followed by cooling in an ice bath and continued stirring for 1 h. The reaction solution was analyzed by HPLC. Analysis of the reaction solution by HPLC confirmed the formation of 13.7 g (82.3 mmol, conversion: 85.3%) of 2-bromo-4-methyl-1H-imidazole. The reaction solution was concentrated under reduced pressure and purified by silica gel column chromatography (eluent: ethyl acetate/hexane mixed system). The product-containing fractions were collected, and after evaporation to remove volatile components, 2-bromo-4-methyl-1H-imidazole crystals were obtained in a yield of 12.6 g (yield: 78.1%). The obtained crystals were further confirmed to be 2-bromo-4-methyl-1H-imidazole by comparing the NMR spectrum of the product with that of the standard sample.
