I am trying to synthesize imidazole compounds from diamines and aldehydes. I saw a reaction where a diamine, aldehyde, and ammonium acetate are mixed together in equal molar amounts at 75 degrees Celcius in Ethanol, however, my NMR shows the formation of a Schiff base rather than the desired imidazole compound. I have attached the reaction which I have used from the literature and I have attached the ligand I would like to synthesize. What can/should I do differently?
Note that the reaction involves an oxidation - you may need to conduct the reaction in the presence of air, and not under nitrogen, or provide some other reducible species. A blanket of refluxing solvent can block out oxygen as well. Alternatively, a catalytic amount of Pd or Pt might let the reaction evolve H2.
To prepare imidazole compounds Take equimolar o-phehylene diamine diamines and aldehydes , add to it Trifluoroacetic acid & reflux gently for 3 hrs., then cool and pour in ice-cold water when imidazole separates out, as solid.
Shabaaz Abdullah attached please find a paper in which your compound is described.
Recently metallophthalocyanines are also used for the synthesis of imidazole compounds from diamines and aldehydes. For reaction, potassium tert-butoxide is use as a base and DMSO is use as a solvent. The reaction is conduct in the presence of oxygen and proceed at 110°C for 8 to 10 hours.
Mr. S. Abdullah,
Try with lewis acids like AlCl3. You may also perform the reaction with catalytic amount of p-toluene sulfonic acid in toluene at reflux temperature.
https://www.organic-chemistry.org/synthesis/heterocycles/imidazoles.shtm
Shabaaz Abdullah just in case you want to buy the compound: It is also commercially available from various sources (see attached).
Note that the reaction involves an oxidation - you may need to conduct the reaction in the presence of air, and not under nitrogen, or provide some other reducible species. A blanket of refluxing solvent can block out oxygen as well. Alternatively, a catalytic amount of Pd or Pt might let the reaction evolve H2.
Dear Shabaaz Abdullah you're welcome! Please tell us on occasion if your experiments were successful. Good luck!
The Schiff base is an intermediate on the way to the imidazole, so you do want it to form... you just don't want the reaction to stop at that stage. Fusing the diamine with a methyl ester should work - just add a trace of acid, and raise the temperature until something happens.
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