2-Benzoyloxy-1,4-naphthoquinone (1.39 g, 5 mmol), trimethylsilylpropionic acid (1.09 g, 7.5 mmol) and silver nitrate (523 mg, 3 mmol) were suspended in 40 ml aqueous acetonitrile (1:1) and then heated to 65° C. Ammonium persulphate (1.71 g, 7.5 mmol) in 20 ml water was added slowly and dropwise over 30 minutes to the mixture. The reaction mixture was stirred at this temperature for a further hour and then cooled, diluted with diethyl ether and the aqueous phase removed. The organic extract was washed with saturated sodium bicarbonate solution, then brine and dried over anhydrous magnesium sulphate. After concentration in vacuo, the crude material was chromatographed using petroleum ether/ethyl acetate as eluent to give 2-benzoyloxy-3-(2'-trimethylsilylethyl)-1,4-naphthoquinone (879 mg) which was recrystallised from methanol, m.pt.: 92-95° C. NMR peaks at: 184.4, 178.2, 150.3, 142.6, 134.0, 133.8, 132.1, 130.9, 126.6, 126.6; 18.8, 16.2; -2.0; 163.8, 128.0, 128.7, 130.4, 134.2 (PhCO).
