C[Si](C)(C)CCOC[O:7][C:8]1[CH:9]=[N:10][CH:11]=[CH:12][CH:13]=1.O.[C:17]1(C)[CH:22]=C[C:20](S(O)(=O)=O)=[CH:19][CH:18]=1.C(=O)(O)[O-].[Na+].[O:33]1[CH2:37][CH2:36][CH2:35][CH2:34]1>>[CH2:19]([C:18]1[CH:17]=[CH:22][C:36]([C:37]([C:13]2[CH:12]=[CH:11][N:10]=[CH:9][C:8]=2[OH:7])=[O:33])=[CH:35][CH:34]=1)[CH3:20]Next, a mixture of 4-(4-ethylbenzoyl)-[3-[2-(trimethylsilyl)ethoxymethoxy]pyridine (3.4 g), p-toluenesulfonic acid monohydrate (3.46 g, 18.2 mmol) and tetrahydrofuran (60 mL) was stirred at 80° C. for 2 hours. After cooling to room temperature, the reaction mixture was poured into saturated aqueous sodium bicarbonate and extracted twice with ethyl acetate. The organic layers were dried over anhydrous magnesium sulfate and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography (hexane:ethyl acetate=50:50) to give the titled compound (1.57 g, 83%).
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