[C:1]1([CH2:7][C:8]([OH:10])=[O:9])[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=1.Cl(O)(=O)(=O)=O.C([O-])(O)=O.[Na+].CCOCC.[C:26](OC(C)=O)([CH3:29])([CH3:28])[CH3:27]>>[C:1]1([CH2:7][C:8]([O:10][C:26]([CH3:29])([CH3:28])[CH3:27])=[O:9])[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=1A solution of 2-phenylacetic acid (12 g, 88 mmol) in t-BuOAc (250 mL) in a 1 L round-bottomed flask was treated with perchloric acid (70% redistilled, 0.212 mL, 3.53 mmol) and stirred at room temperature for 20 hours. The solution was transferred very slowly to stirred mixture of saturated aqueous NaHCO3 and Et2O. Gas evolution was observed. The resulting layers were separated and the organic layer was washed with saturated aqueous NaHCO3, dried over MgSO4, filtered, and concentrated to give Intermediate S-3D (11.6 g, 68% yield): 1H NMR (500 MHz, chloroform-d) δ 7.34-7.29 (m, 2H), 7.28-7.22 (m, 3H), 3.52 (s, 2H), 1.44 (s, 9H).
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