To a solution of diethyl 3,5-pyrazoledicarboxylate (2.17 g, 10 mmol) in acetonitrile (10 ml), under nitrogen, was added potassium carbonate (2.07 g, 15 mmol), and 2-bromoethoxy-t-butyldimethylsilane (2.90 g, 12 mmol). The mixture was stirred at reflux for 18 hr. It was then cooled to room temperature, diluted with ethyl acetate (20 ml), and filtered through Magnesol. The filter pad was eluted with 2×10 ml of ethyl acetate, and the combined filtrate was evaporated. The residue was dissolved in hexanes and passed through a column of silica gel (70 g). After eluting with hexanes (100 ml), the column was eluted with ethyl acetate. The ethyl acetate eluent was evaporated to give 3.71 g of a colorless oil; MS m/e 371 (MH+).
