C1O[C:4]2([CH2:9][CH2:8][CH:7]([C:10]3[CH:11]=[N:12][CH:13]=[CH:14][CH:15]=3)[CH2:6][CH2:5]2)[O:3]C1.Cl>C1COCC1>[N:12]1[CH:13]=[CH:14][CH:15]=[C:10]([CH:7]2[CH2:6][CH2:5][C:4](=[O:3])[CH2:9][CH2:8]2)[CH:11]=1A solution of 4-(3-pyridyl)cyclohexanone ethylene ketal prepared above (27 g, 120.0 mmol) in THF (200 mL) and 2 N HCl (100 mL) was stirred at 23° C. for 23 h. The reaction was quenched by adding saturated aqueous NaHCO3 and diluted with EtOAc (200 mL). The aqueous layer was extracted with CH2Cl2 (100 mL×4) and the combined organic layers were washed with brine (200 mL), dried with MgSO4 and concentrated in vacuo. The crude product was filtered through a plug of silica gel, washing with 5% MeOH in CH2Cl2, which afforded 4-(3-pyridyl)cyclohexanone.
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