1-Dimethylsulfamoyl-2-t-butyldimethylsilyl-5-imidazolecarboxaldehyde → 5-Cyclohexylmethyl-2-tert-butyldimethylsilyl-1-dimethylsulfamoyl imidazole

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Reaction Steps

2-Tert-butyldimethylsilyl-1-dimethylsulfamoyl imidazole (1) (4.1 g, 14.2 mmol) is taken up in 47 mL of anhydrous THF and cooled to −20° C. n-BuLi (8.9 mL, 14.2 mmol) is added dropwise to the solution of (1). The resultant solution is stirred at −20° C. for 45 min. Cyclohexylmethyl iodide (2) (3.14 g, 14 mmol) is then added dropwise to the reaction mixture. Then reaction is warmed to rt and stirred overnight. The next day the reaction is quenched with saturated ammonium chloride and diluted with water. The mixture is extracted with ethyl acetate (3×100 mL). The organic layers are combined and washed with water followed by brine. The organic phase is dried over sodium sulfate and the solvent removed under reduced pressure. Flash chromatography (4:1 ethyl acetate/hexane) affords 2.26 g (5.6 mmol) of 5-cyclohexylmethyl-2-tert-butyldimethylsilyl-1-dimethylsulfamoyl imidazole (3). (3) (2.26 g, 5.6 mmol) is taken up in 56 mL of THF and cooled to 0° C. A 1M solution of TBAF in THF (5.6 mL, 5.6 mmol) is added dropwise to the solution of (3). The reaction is warmed to rt and stirred overnight. The next day the reaction is quenched with water and then extracted with ethyl acetate. The organic layer is washed with water followed by brine. The organic phase is dried over sodium sulfate and the solvent removed under reduced pressure. Flash chromatography (1:1 ethyl acetate/hexane) affords 1.2 g (4.42 mmol) of 5-cyclohexylmethyl-1-dimethylsulfamoyl imidazole (4). (4) (1.2 g, 4.42 mmol) is taken up in 25 mL of a 1.5N HCl solution and heated at reflux for 2 h. The reaction is cool to rt and diluted with ethyl acetate. The mixture is brought to pH 13 with 2N NaOH and then extracted with chloroform (4×100 mL). The organic layers are combined and washed with water followed by brine. The organic phase is dried over sodium sulfate and the solvent removed under reduced pressure. Flash chromatography (9:1 chloroform/methanol) affords 700 mg (4.27 mmol) of 4(5)-cyclohexylmethyl-1H-imidazole (5) (J-1).

Provenance & Evidence