S(Cl)(Cl)=O.[CH2:5]1[O:21][C:8]2([CH2:13][CH2:12][C:11](O)([C:14]3[CH:15]=[N:16][CH:17]=[CH:18][CH:19]=3)[CH2:10][CH2:9]2)[O:7][CH2:6]1.[OH-].[Na+]>N1C=CC=CC=1>[CH2:6]1[O:7][C:8]2([CH2:13][CH2:12][C:11]([C:14]3[CH:15]=[N:16][CH:17]=[CH:18][CH:19]=3)=[CH:10][CH2:9]2)[O:21][CH2:5]1Thionyl chloride (45 mL, 622.5 mmol) was slowly added to a solution of 4-hydroxy-4-(3-pyridyl)cyclohexanone ethylene ketal (prepared as in step a, 29.3 g, 124.5 mmol) in pyridine (250 mL) at −10° C. After stirring at 0° C. for 2.5 h, the reaction mixture was poured onto ice and adjusted to pH 8 with 2 N NaOH. The aqueous layer was extracted with CH2Cl2 (100 mL×3) and the combined organic layers were washed with brine (200 mL), dried with MgSO4, and concentrated in vacuo to afford crude 4-(3-pyridyl)cyclohex-3-en-1-one ethylene ketal, which was used without further purification.
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