Sodium hydride (0.35 g, 8.6 mmol, 60% in mineral oil) was added to a solution of 4-tert-butyloxycarbonyl-piperazin-2-one (0.86 g, 4.3 mmol) in dimethylformamide (20.0 mL) at 0° C. The reaction was stirred at 0° C. for 0.5 h. To this mixture was added 2-bromoethoxy-tert-butyldimethylsilane (2.3 mL, 10.8 mmol) and the reaction was stirred for 2 h at room temperature. The reaction mixture was quenched with a dilute aqueous solution of sodium bicarbonate and extracted with methylene chloride. The organic extracts were washed with brine and dried over anhydrous sodium sulfate. Purification of the crude residue by flash column chromatography (silica gel, eluting with 20% ethyl acetate in hexanes) gave 4-tert-butyloxycarbonyl-1-[2-(tert-butyldimethylsilyloxy)ethyl]-piperazin-2-one (1.17 g, 76%).
