Pyridine → isobutyl 3-fluoro-4-(4-oxo-3,4-dihydropyridin-1(2H)-yl)phenylcarbamate

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To a cold (0° C.) stirring solution of the aniline from step 4 (62.0 g, 300.7 mmol) and pyridine (29.1 ml, 360.8 mmol) in dichloromethane (1095 ml) is added isobutyl chloroformate (42.9 ml, 330.7 mmol), and the mixture is stirred at ambient temperature for 90 min. Upon completion of the reaction the solvent is removed in vacuo, and the residual material is redissolved in dichloromethane (800 ml) and ethyl acetate (1100 ml). The mixture is washed with 10% aqueous HCl (1100 ml), and aqueous layer is extracted with 1:9/dichloromethane:ethyl acetate (1100 ml). The organic layers are combined and washed with brine (1100 ml). The organic layer is dried over MgSO4 and filtered. The filtrate is concentrated in vacuo. The residual material is recrystallized in 1:9/dichloromethane:ethyl acetate to afford 66.9 g (72% yield) of the title compound as a brown solid. 1H NMR (400 MHz, DMSO-d6) δ 0.93 (d, 6 H), 1.93 (m, 1 H), 2.47 (m, 2 H), 3.84 (m, 2 H), 3.89 (m, 2 H), 4.96 (d, 1 H) 7.29 (m, 2 H), 7.48 (m, 2 H), 9.92 (brs, 1 H).

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