4,6-Diphenylthieno[3,4-d]-1,3-dioxol-2-one 5,5-Dioxide

Experimental procedure: A mixture of 4,6-diphenylthieno[3,4-d]-1,3-dioxol-2-one 5,5-dioxide (1.00 g, 3.06 mmol), phenylacetic acid (0.41 g, 3.01 mmol) and pyridine (0.24 g, 3.03 mmol) in dichloromethane (25 mL) is stirred for 2 h at room temperature. Subsequently, triethylamine (0.31 g, 3.06 mmol) is added, the solution turning orange-red. After 10 min stirring, a solution of 1 (0.45 g, 2.51 mmol) in dichloromethane (15 mL) is added dropwise. Stirring is continued for 2 h, giving a yellow solution. The mixture is extracted twice with 20% citric acid (30 mL), three times of saturated aqueous NaHCO₃ (50 mL), 20% citric acid (30 mL) and water (30 mL). The organic layer is dried over MgSO₄ and the solvent is removed in vacuo. Recrystallization of the remaining solid from acetonitrile at -20 °C gives 2 (0.61 g, 82% yield) as white needles.