tert-Butyldimethylsilyl chloride → 2-(tert-Butyldimethylsilyl)-N,N-dimethyl-1H-imidazole-1-sulfonamide

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Imidazole (Intermediate L1, available from Aldrich, 20.0 g, 0.29 mol), triethylamine (41.0 mL, 0.29 mol) and N,N-dimethylsulfamoyl chloride (31.6 mL, 0.29 mol) were added to benzene (320 mL). The reaction was stirred for 48 h at rt and then filtered. The filtrate was collected and concentrated under reduced pressure. Vacuum distillation of the crude produc (˜0.5 mmHg, 115–118° C.) afforded dimethylsulfamoyl)imidazole (Intermediate L2) 38.7 g (76%) as a clear and colorless oil. Upon cooling the product solidifies to give white crystals. 1-(Dimethylsulfamoyl)imidazole (Intermediate L2) (18.8 g, 0.11 mol) was added to THF (430 mL). The solution was cooled to −78° C. A solution of n-BuLi (70.9 mL, 1.6 M in hexane) was added dropwise to the reaction mixture. Upon completion, the solution was stirred for 1 h at −78° C. t-Butyldimethylsilylchloride (TBSCI) (17.8 g, 0.12 mol) in THF (50 mL) was added via cannula to the mixture. After the addition was completed the reaction mixture was warmed slowly to rt and stirred for 24 h. The mixture was diluted with water and the organic layer separated. The organic phase was washed with brine and then dried over Na2SO4. The mixture was filtered and the filtrate concentrated under reduced pressure. Column chromatography on SiO2 with 20% ethyl acetate/hexane afforded 1-dimethylsulfamoyl-2-t-butyldimethylsilyl imidazole (Formula 13) as a light yellow solid. Recrystallization from pentane gave 30 g (94%) of white crystals.

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