Methyl bromoacetate → Methyl 6-bromoimidazo(1,2-a)pyridine-3-carboxylate

Temperature

90 °C

Reaction mixture containing N′-(5-bromopyridin-2-yl)-N,N-dimethylformimidamide (6.5 g, 28.5 mmol), methyl 2-bromoacetate (5.6 g, 3.5 mL, 37.0 mmol) and NaHCO3 (4.1 g, 48.8 mmol) in i-PrOH (60 mL) was heated at 90° C. under nitrogen. The heating was stopped after 12 h and cooled the dense heterogeneous reaction mixture to room temperature. The reaction mixture was concentrated and diluted with water. The resultant slurry was collected by suction filtration and obtained methyl 6-bromoimidazo[1,2-a]pyridine-3-carboxylate (6.9 g) as a tan white solid upon drying. 1H NMR (300 MHz, DMSO-d6): δ 9.31 (d, J=1.8 Hz, 1H), 8.31 (s, 1H), 7.80 (d, J=9.5 Hz, 1H), 7.71 (dd, J=9.5, 1.6 Hz, 1H), 3.88 (s, 4H). Ester hydrolysis was done by stirring a solution of methyl 6-bromoimidazo[1,2-a]pyridine-3-carboxylate (2.5 g), LiOH.H2O (1.2 g) in THF/MeOH/H2O (1/1/1, 75 mL) at room temperature. Reaction mixture was concentrated upon complete hydrolysis of ester to corresponding acid, diluted with water/ice and acidified with 2N. aq HCl until pH 6. The resulting solid was filtered, suction dried followed by drying under P2O5 under vacuum to obtain 6-bromoimidazo[1,2-a]pyridine-3-carboxylic acid (2.2 g) as a white solid. 1H NMR (300 MHz, DMSO-d6) δ 13.27 (s, 1H), 9.36 (s, 1H), 8.24 (s, 1H), 7.77 (d, J=9.5 Hz, 1H), 7.67 (d, J=9.5, 1.7 Hz, 1H).

1. customReaction mixture
2. temperaturecooled the dense heterogeneous reaction mixture to room temperature
3. concentrationThe reaction mixture was concentrated
4. additiondiluted with water
5. filtrationThe resultant slurry was collected by suction filtration

ORD record

ord-d1b02a53cab941d0bd97f99d18bf3dcb

Source dataset

uspto-grants-2015_09

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US09145433B2