DBU Catalysis: An Efficient Synthetic Strategy for 5,7-disubstituted-1,2,4- triazolo[1,5-a]pyrimidines

An efficient and facile DBU catalysed synthesis of highly significant motif 5,7-disubstituted-1,2,4-triazolo[1,5-a]pyrimidines under solvent-free condition has been reported.

To a round bottom flask, 1.0 mmol of chalcone (1), 1.5 mmol of 3-amino-1,2,4- triazole (2) and 30 mol% of DBU were added at 70 °C and stirred in solvent-free condition. After the completion of the reaction (monitored by TLC), water (10 ml) was added. The aqueous layer was extracted with ethyl acetate (3 ×10 ml). The combined organic layers were dried over anhydrous Na2SO4. The combined organic layers were evaporated under reduced pressure and the resulting crude product was purified by column chromatography by using ethyl acetate and hexane as eluent.

Reaction using chalcone and 3-amino-1,2,4-triazole as model substrates were carried out under different reaction conditions and it was observed that 30 mol% of DBU under the solvent-free condition at 70 °C was the optimum temperature for the proposed synthesis.

Use of DBU (an organocatalyst) as a base, operational simplicity, high yield of products and short reaction time are some of the significant advantages associated with the proposed strategy.