[Cl:1][C:2]1[CH:3]=[N:4][CH:5]=[C:6]([F:14])[C:7]=1[N:8]1[CH2:13][CH2:12][NH:11][CH2:10][CH2:9]1.[O:15]1[CH2:18][C:17](=O)[CH2:16]1.C(O[BH-](OC(=O)C)OC(=O)C)(=O)C.[Na+].CO>C1COCC1>[Cl:1][C:2]1[CH:3]=[N:4][CH:5]=[C:6]([F:14])[C:7]=1[N:8]1[CH2:13][CH2:12][N:11]([CH:17]2[CH2:18][O:15][CH2:16]2)[CH2:10][CH2:9]1
To a suspension of 1-(3-chloro-5-fluoropyridin-4-yl)piperazine (900 mg, 4.173 mmol) in THF (9.000 mL) was added 3-oxetanone (601.4 mg, 8.346 mmol). To this mixture, under N2, was added sodium triacetoxyborohydride (2.034 g, 9.598 mmol) portionwise over 5 min and the reaction mixture was stirred at RT overnight. MeOH (2 ml) was added to the flask before the mixture was concentrated in vacuo. The residue was partitioned between water (50 ml) and EtAOc (50 ml). The aqueous phase was basified to pH 7-8 with NH4OH. Combined organics washed with brine (30 ml), dried over Na2SO4, filtered and concentrated in vacuo to afford 1-(3-chloro-5-fluoro-4-pyridyl)-4-(oxetan-3-yl)piperazine as a cream solid that was used in next step without further purification. MS (ES+) 272.1.
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