Synthesis of 3 . A mixture of 2 (1.1 g, 3.6 mmol), zinc oxide (0.160 g, 0.196 mmol) and acetic anhydride (0.37 g, 3.6 mmol) in acetic acid (4.3 g, 72 mmol) was stirred at 30°C for 2 d. The reaction was quenched with saturated NaHCO3, and the mixture was extracted with Et2O. The combined organic layer was washed with H2O and dried over anhydrous Na2SO4. The solvent was removed in vacuo, and the residue was purified by flash column chromatography on silica gel (hexane/Et2OÂ =Â 2/1) to give 0.97 g of 3 as a pale yellow viscous liquid (95%).