1121057-77-9

Step 4. tert-Butyl 5-(((trifluoromethyl)sulfonyl)oxy)-3,4-dihydropyridine-1(2H)-carboxylate (1.45 g, 4.38 mmol) and pinacol ester of bisboronic acid (1.223 g, 4.81 mmol) were dissolved in dioxane (24 mL). To this solution was added potassium acetate (1.289 g, 13.13 mmol) and PdCl2(dppf)-CH2Cl2 adduct (0.107 g, 0.131 mmol). The reaction mixture was purged for 5 min under nitrogen protection and subsequently heated in an oil bath at 80 °C overnight. After completion of the reaction, the mixture was partitioned between ethyl acetate and water. The organic layer was separated, washed with brine, dried over anhydrous sodium sulfate, filtered and concentrated. The residue was purified by fast chromatography using a 0-30% ethyl acetate/heptane gradient elution to afford the target product tert-butyl 5-boronic acid pinacol esteryl-3,4-dihydropyridine-1(2H)-carboxylate as a highly viscous liquid (1.2 g, 89% yield).LCMS (m/z): 254.1 (MH+ - tBu), retention time 1.21 min.

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