2-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane → 1-Methyl-4-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)piperazine

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Reaction Steps

To a cooled (−78° C.) solution of 1-(4-Bromo-phenyl)-4-methyl-piperazine (8.05 g, 31.54 mmol, CAS 130307-08-3) in dry THF (500 ml) are added dropwise 28 ml of a solution of n-BuLi (2.5M in hexanes, 69 mmol). After 1 h, of 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (13.1 ml, 63.1 mmol) in solution in dry THF (20 ml) are introduced. After complete addition, the reaction mixture is allowed to slowly warm up to RT. The reaction mixture is then diluted with 200 ml of a saturated solution of NH4Cl and most of the THF is removed by evaporation. The residue is diluted with EtOAc and the phases are separated. The aqueous phase is re-extracted three times with EtOAc and the combined organic extracts are washed twice with de-ionized water, once with saturated brine, dried over Na2SO4, filtered and concentrated in vacuo. The residue is purified by chromatography (silicagel, CH2Cl2/EtOH 9:1) to afford the title compound as a colorless solid, Rt=0.851 min (Acquity HPLC BEH C18, 2.1×50 mm, 1.7 micron, detection 215 nM, 0.1 min 2% CH3CN in H2O, 2% to 100% CH3CN in H2O in 1.5 min, 0.4 min 100% CH3CN+0.1% TFA, flow rate 1.0 ml/min); MS: 303 (M+1)+.

Provenance & Evidence