1H-IMIDAZOL-2-YLMETHYLAMINE DIHYDROCHLORIDE was prepared as follows:
1) 1H-Imidazol-2-carboxaldehyde
The pH of the aqueous solution containing 1H-imidazol-2-carboxaldehyde hydrochloride was adjusted to 9.5 or 6.5 with NaOH. Then, it was extracted with dichloromethane using a continuous extraction apparatus. Finally, the organic layer was dried with anhydrous Na2SO4 and evaporated to dryness under reduced pressure.
Solid 1H-imidazolium-2-carboxaldehyde was obtained by crystallization from methanol/water (4.42 g, 92% or 4.29 g, 89% at pH 9.5 or 6.5, respectively), yield (4.42 g, 92% or 4.29 g, 89% at pH 9.5 or 6.5, respectively). Melting point: 206-207 °C.
2) 1H-Imidazolium-2-carboxaldehyde formaldehyde oxime
Imidazolium-2-carboxaldehyde (2.0 g, 20.8 mmol) was dissolved in anhydrous ethanol (320 mL), and then sodium carbonate (1.0 g) and hydroxylamine hydrochloride (1.5 g, 21.6 mmol) were added to the solution. The mixture was refluxed for 2 hours, and then the solvent was evaporated under reduced pressure.
The crude product was purified by TLC silica gel chromatography using CH2Cl2/methanol (90:10 v/v) as eluent to give 1H-imidazolium-2-carboxaldehyde oxime (1.43 g, 62%) as a yellow solid. Melting point: 171–172 °C.
3)1H-IMIDAZOL-2-YLMETHYLAMINE DIHYDROCHLORIDE
Sodium borohydride (200 mg, 5.3 mmol) was added to a solution of 1H-imidazolium-2-carboxaldehyde oxime (1.0 g, 10.4 mmol) in anhydrous ethanol (100 mL). The mixture was stirred at 20 °C for 2 h, then poured onto water (50 mL), and extracted with ethyl acetate (3 × 50 mL). The combined organic layers were dried over anhydrous Na2SO4 and evaporated to dryness under reduced pressure.
The crude product was crystallized from methanol/water to give 1H-IMIDAZOL-2-YLMETHYLAMINE DIHYDROCHLORIDE, a yellow solid (0.77 g, 75%).
