2-Aminopyridine → Ethyl imidazo[1,2-a]pyridine-2-carboxylate

HRID 1048711Notes

Reaction equation

HRID 1048711 reaction equation
[NH2:1][C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][N:3]=1.Br[CH2:9][C:10](=O)[C:11]([O:13][CH2:14][CH3:15])=[O:12]>O1CCCC1.C(O)C>[N:1]1[C:10]([C:11]([O:13][CH2:14][CH3:15])=[O:12])=[CH:9][N:3]2[CH:4]=[CH:5][CH:6]=[CH:7][C:2]=12

Participants

5

Reactant 2

HCID 104392-AminopyridineHCID 66144Ethyl bromopyruvate

Product 1

HCID 818807Ethyl imidazo[1,2-a]pyridine-2-carboxylateYield 84.7%

Reagents, catalysts & solvents 2

HCID 702EthanolSolvent2×HCID 8028TetrahydrofuranSolvent

Procedure

3 g (31.9 mmol) of 2-aminopyridine were dissolved in 65 ml of tetrahydrofurane with magnetic stirring. The addition of 4.44 ml (31.9 mmol) of ethyl bromopyruvate caused precipitation of a solid. The heterogenous mixture was stirred with reflux for 4 h. After returning to r.t., the solid was isolated by filtration and taken up in 65 ml of ethanol in order to be stirred with reflux in 65 ml of ethanol for 16 h. After returning to r.t., the solid was isolated by filtration. The filtrate was placed in ice in order to facilitate crystallization of the product which was collected by filtration and thus so forth until the liquid phase remained limpid. The solid was rinsed with 30 ml of diisopropyl ether and dried in a vacuum bell jar in order to obtain 5.14 g (yield=84%) of ethyl imidazo[1,2-a]pyridine-2-carboxylate as a white powder. LC-MS: m/z=191 (MH+); UV purity at 254 nm=99%. 1H NMR (300 MHz, DMSO) δ 8.95 (s, 1H), 8.84 (d, J=6.8 Hz, 1H), 7.98-7.80 (m, 2H), 7.46 (t, J=7.2 Hz, 1H), 4.43 (q, J=7.1 Hz, 2H), 1.35 (d, J=7.1 Hz, 3H).

Workup

  1. customprecipitation of a solid
  2. temperaturewith reflux for 4 h
  3. customAfter returning to r.t.
  4. customthe solid was isolated by filtration
  5. stirringto be stirred
  6. customAfter returning to r.t.
  7. customthe solid was isolated by filtration
  8. customcrystallization of the product which
  9. filtrationwas collected by filtration and thus so forth until the liquid phase
  10. washThe solid was rinsed with 30 ml of diisopropyl ether
  11. customdried in a vacuum bell jar in order

Sources & evidence

ORD record
ord-37370a85ac524820997f4799405bc2fc
Source dataset
uspto-grants-2016_07
Patent number
US09381191B2

Reaction notes

Loading…