N-bromobutanimide → 2-methoxyethyl 4-(7-(bis((2-(trimethylsilyl)ethoxy)methyl)amino)-6-bromo-3-(1-phenyl-1H-pyrazol-4-yl)pyrazolo[1,5-a]pyrimidin-5-yl)-1-(2-methoxyethoxy)cyclohexanecarboxylate

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To a solution of 2-methoxyethyl 4-(7-(bis((2-(trimethylsilyl)ethoxy)methyl)amino)-3-(1-phenyl-1H-pyrazol-4-yl)pyrazolo[1,5-a]pyrimidin-5-yl)-1-(2-methoxyethoxy)cyclohexanecarboxylate (2.28 g, 2.87 mmol) in CH3CN (50 mL) was added NBS (511 mg, 2.87 mmol) and stirred at rt for 30 min. Both TLC and LCMS showed complete conversion. All the volatiles were removed under reduced pressure and the residue was purified by a SiO2 column (0-30%, EtOAc/Hexanes, Rf=0.65 in 50% EtOAc) to afford 2-methoxyethyl 4-(7-(bis((2-(trimethylsilyl)ethoxy)methyl)amino)-6-bromo-3-(1-phenyl-1H-pyrazol-4-yl)pyrazolo[1,5-a]pyrimidin-5-yl)-1-(2-methoxyethoxy)cyclohexanecarboxylate as a yellow oil (2.50 g). HPLC-MS TR=1.99 min (UV 254 nm, 3 min method); mass calculated for formula C40H61BrN6O7Si2 872.3, observed LCMS m/z 873.3 (M+H).

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