Acetic Acid → Methyl 3-amino-6-bromo-5-(trifluoromethyl)picolinate

関与物質

反応手順

3-Amino-5-trifluoromethyl-pyridine-2-carboxylic acid methyl ester (9.49 g, 43.16 mmol) was suspended in water (300 ml). Sulfuric acid (4.60 ml, 86 mmol) was added followed by dropwise addition over 30 minutes of a solution of bromine (2.222 ml, 43.1 mmol) in acetic acid (29.6 ml, 517 mmol). The reaction mixture was stirred at RT for 18 hours. A further 100 ml of water was added, followed by a further 0.25 equivalents of the bromine/AcOH mixture (550 μL bromine in 7.4 ml AcOH) and the reaction mixture stirred at RT for an additional 90 minutes. The reaction mixture was diluted with 500 ml water and neutralised by addition of solid NaHCO3 (˜85 g). The suspension was extracted with DCM (3×300 ml) and the combined organic phases washed with sat.NaHCO3(aq) (250 ml), water (250 ml) and brine (100 ml), dried (MgSO4) and concentrated in vacuo. The crude material was recrystallised from boiling MeOH (˜300 ml) to give the title product as a pale orange solid m/z 301.0 [M+H]+1H-NMR: [400 MHz, DMSO-d6 δH 7.77 (1H, s, ArH), 7.17 (2H, s, NH2), 3.86 (3H, s, ArCO2CH3).

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