General procedure for the synthesis of 2-(chloromethyl)-1-methyl-1H-imidazole hydrochloride (BB7) from 1-methyl-2-hydroxymethyl-1H-imidazole (BB6): to a solution of BB6 (35.5 g, 316.96 mmol) in dichloromethane (DCM, 1500 mL) was slowly added thionyl chloride (SOCl2, 330 mL, 4436 mmol ). The reaction mixture was gradually warmed to room temperature and stirred continuously for 5 hours. Upon completion of the reaction, the mixture was concentrated to remove the solvent. The residue was washed sequentially with dichloromethane (DCM, 2 × 500 mL) and ether (Et2O, 2 × 200 mL) to give the final target product BB7 (50 g, 95% yield) as an off-white solid. Thin-layer chromatography (TLC) showed an Rf value of 0.4 (unfolding agent: ethyl acetate).1H NMR (400 MHz, DMSO-d6) data were as follows: δ 7.76 (1H, apparent double peaks), 7.70 (1H, apparent double peaks), 5.17 (2H, single peak), 3.87 (3H, single peak); mass spectrometry (MS) showed an m/z of 131 ([M+H]+ ).
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