Imidazole → 4-[2-(Tert-butyldimethylsilanyloxy)-2-methylpropoxy]-3,5-dimethylbenzonitrile

Participants

Reaction Steps

To a solution of 4-(2-hydroxy-2-methylpropoxy)-3,5-dimethyl benzonitrile (2.90 g, 13.2 mmol) in anhydrous DMF (20 mL) was added imidazole (2.7 g, 40 mmol) and tert-butyldimethylsilylchloride (2.19 g, 14.6 mmol). The reaction mixture was stirred at room temperature under nitrogen for 3 d. Water (200 mL) was added and the mixture was extracted with ethyl acetate (200 mL). The organic layer was washed with water (2×100 mL) and brine (100 mL), and dried over anhydrous Na2SO4. The solvent was removed under reduced pressure and the crude compound was purified by column chromatography to give 4-[2-(tert-butyldimethylsilanyloxy)-2-methylpropoxy]-3,5-dimethylbenzonitrile (2.24 g, 54%). N-Butyl lithium (6.2 mL, 6.6 mmol, 1.6 M solution in hexanes) was added to a solution of 2,4-dimethoxy-6-N-dimethylbenzamide (0.9 g, 4.3 mmol) in anhydrous THF (10 mL) drop-wise at −10° C. over a period of 10 min under nitrogen. The stirring was continued at 0° C. for 1 h. The reaction mixture was cooled to −50° C. A solution of 4-[2-(tert-butyldimethylsilanyloxy)-2-methylpropoxy]-3,5-dimethylbenzonitrile (1.58 g, 4.73 mmol) in anhydrous THF (5 mL) was quickly added. The cooling bath was removed and the reaction mixture was allowed to warm to room temperature. The stirring was continued at room temperature for 1 h. An aqueous ammonium chloride solution (10 mL) was added followed by ethyl acetate (100 mL). The organic layer was separated, washed with water (10 mL) and dried (Na2SO4). The solvent was removed under reduced pressure and the crude compound was purified by column chromatography (silica gel 230-400 mesh; 0-5% methanol in CH2Cl2 as eluent) to give 3-{4-[2-(tert-butyldimethylsilanyloxy)-2-methylpropoxy]-3,5-dimethylphenyl}-6,8-dimethoxy-2H-isoquinolin-1-one (0.82 g, 37%), as a white solid.

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