Aim and Objective:
In this work, water was used as solvent for the eco-friendly synthesis of imines
under microwave irradiation. In the first step of the study, 5-pyridinyl-3-amino-1,2,4-triazole hydrochlorides
were synthesized in the reaction of amino guanidine hydrochloride with different pyridine carboxylic acids under
acid catalysis. A green method for 5-pyridinyl-3-amino-1,2,4-triazoles was developed with the assistance
of microwave synthesis. In the second step, the eco-friendly synthesis of imines was achieved by reacting 5-
pyridinyl-2H-1,2,4-triazol-3-amine hydrochlorides with salicylic aldehyde derivatives to produce 2-(5-
pyridinyl-2H-1,2,4-triazol-3-ylimino)methyl)phenol imines.
Materials and Methods:
Microwave experiments were done using a monomode Anton Paar Monowave 300
microwave reactor (2.45 GHz). Reaction temperatures were monitored by an IR sensor. Microwave experiments
were carried out in sealed microwave process vials G10 with maximum reaction volume of 10 mL.
Results:
When alternative methods were used, it was impossible to obtain good yields from ethanol. Nevertheless,
the use of water was successful for this reaction. After 1-h microwave irritation, a yellow solid was obtained
in 82% yield.
Conclusion:
In this work an eco-friendly protocol for the synthesis of Schiff bases from 5-(pyridin-2-, 3- or 4-
yl)-3-amino-1,2,4-triazoles and substituted salicylic aldehydes in water under microwave irradiation was developed.
Under the found conditions the high yields for the products were achieved at short reaction time and
with an easy isolation procedure.