Hydrochloric Acid → 3-Amino-6-(2,6-difluorophenyl)-5-fluoropicolinic acid

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반응 단계

To a solution of methyl 3-amino-5-fluoropicolinate (1.0 equiv.) in DME/2M Na2CO3 (3:1, 0.05 M) equipped with microwave vial was added 2,6-difluorophenylboronic acid (3.0 equiv.) and Pd(dppf)Cl2-DCM (0.1 equiv.). The reaction mixture was heated to 140° C. for 10 min in microwave reactor. After 2,6-difluorophenylboronic acid (3.0 equiv.) was added more, the reaction mixture was heated once more to 140° C. for 10 min in microwave reactor. After the reaction mixture was cooled to room temperature, H2O and EtOAc were added and the organic phase was washed with brine, then dried with Na2SO4, and concentrated. The crude material was purified via preparative HPLC. The pure methyl 3-amino-6-(2,6-difluorophenyl)-5-fluoropicolinate was obtained after the pure fractions were neutralized with NaHCO3, extracted with EtOAc, and concentrated (34%). The methyl 3-amino-6-(2,6-difluorophenyl)-5-fluoropicolinate (1.0 equiv.) was dissolved in THF and MeOH (2:1, 0.2 M) followed by addition of LiOH (1.8 equiv., 1 M aqueous solution). After the reaction mixture was stirred for 1.5 h at room temperature, the reaction mixture was quenched with 1 N HCl solution (1.8 equiv.) and extracted with EtOAc. The organic phase was washed with brine, then dried with Na2SO4, and concentrated. The crude 3-amino-6-(2,6-difluorophenyl)-5-fluoropicolinic acid was used for the next step without further purification (88%). LCMS (m/z): 269.0 (MH+); LC Rt=3.26 min.

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