Br[C:2]([CH3:6])([CH3:5])[CH:3]=[O:4].[O:7]1[CH2:10][CH:9]([N:11]2[CH2:16][CH2:15][NH:14][CH2:13][CH2:12]2)[CH2:8]1.CCN(C(C)C)C(C)C>C(Cl)Cl>[CH3:5][C:2]([N:14]1[CH2:15][CH2:16][N:11]([CH:9]2[CH2:10][O:7][CH2:8]2)[CH2:12][CH2:13]1)([CH3:6])[CH:3]=[O:4]A solution of 2-bromo-2-methyl-propanal (696.6 mg, 4.61 mmol) in DCM (10 mL) was cooled with an ice bath and 1-(oxetan-3-yl)piperazine (328 mg, 2.31 mmol), diluted with 5-10 mL of DCM, was slowly added via addition funnel over a 15 min period. Next, Hunig's base (0.4 mL, 2.31 mmol) was added and then the cooling bath was removed. The reaction mixture was stirred at room temperature overnight and the DCM layer was washed three times with 0.5N HCl. The combined aqueous layer was neutralized with NaOH to pH 10-11 and extracted with DCM. The combined organic layer was washed with brine and dried over Na2SO4. Filtration and removal of solvent afforded 2-methyl-2-[4-(oxetan-3-yl)piperazin-1-yl]propanal as a light yellow liquid, which was used directly in the next step without further purification.
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