Abstract
Aims and Objectives: 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.
Materials and Methods: 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.
Results: 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.
Conclusion: 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.
Keywords: Solvent-free, 1, 8-Diazabicyclo[5.4.0]undec-7-ene (DBU), green synthesis, 1, 2, 4-triazolo[1, 5-a]pyrimidines, chalcone, ethyl acetate.
Graphical Abstract
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(a) Mishra, A.; Srivastava, M.; Rai, P.; Yadav, S.; Tripathi, B.P.; Singh, J.; Singh, J. Visible light triggered, catalyst free approach for the synthesis of thiazoles and imidazo[2,1-b] thiazoles in EtOH:H2O green medium. RSC Advances, 2016, 6, 49164-49172.Available at .
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(b)Rai, P.; Mishra, A.; Srivastava, M.; Yadav, S.; Tripathi, B.P.; Singh, J. Singh, J. An amino sugar promoted green protocol: A One-Pot, Meglumine- Catalyzed, multicomponent strategy for synthesis of Multifaceted Pyrroloacridin-1(2H)-one Derivatives. Chemistry Select,, 2017, 2, 2245-2250.Available at.
[http://dx.doi.org/10.1002/slct.201601718.]
(c)Mishra, A.; Rai, P.; Srivastava, M.; Tripathi, B.P.; Yadav, S.; Singh, J. Singh, J. A peerless aproach: Organophotoredox/Cu(I) Catalyzed, regioselective, visible light facilitated, click synthesis of 1,2,3-Triazoles via Azide-Alkyne [3 + 2] Cycloaddition. Catal. Lett.,, 2017, 147, 2600-2611.Available at.
[http://dx.doi.org/10.1007/s10562-017-2156-8.]
(d)Tripathi, B.P.; Mishra, A.; Rai, P.; Pandey, Y.K.; Srivastava, M.; Yadav, S.; Singh, J. Singh, J. A green and clean pathway: One pot, multicomponent, and visible light assisted synthesis of pyrano[2,3-c]pyrazoles under catalystfree and solvent-free conditions. New J. Chem.,, 2017, 4, 11148-11154.Available at.
[http://dx.doi.org/10.1039/C7NJ01688C.]
(e)Mishra, A.; Rai, P.; Pandey, Y.K.; Singh, J. Singh, J. An Eco-Sustainable synthetic approach for 4,5-Dihydro-1H-pyrazoles via DBU catalysis in micellar medium. ChemistrySelect,, 2017, 2, 10979-10983.Available at.
[http://dx.doi.org/10.1002/slct.201702400.]
[http://dx.doi.org/10.1039/C6RA05385H.]
(b)Rai, P.; Mishra, A.; Srivastava, M.; Yadav, S.; Tripathi, B.P.; Singh, J. Singh, J. An amino sugar promoted green protocol: A One-Pot, Meglumine- Catalyzed, multicomponent strategy for synthesis of Multifaceted Pyrroloacridin-1(2H)-one Derivatives. Chemistry Select,, 2017, 2, 2245-2250.Available at.
[http://dx.doi.org/10.1002/slct.201601718.]
(c)Mishra, A.; Rai, P.; Srivastava, M.; Tripathi, B.P.; Yadav, S.; Singh, J. Singh, J. A peerless aproach: Organophotoredox/Cu(I) Catalyzed, regioselective, visible light facilitated, click synthesis of 1,2,3-Triazoles via Azide-Alkyne [3 + 2] Cycloaddition. Catal. Lett.,, 2017, 147, 2600-2611.Available at.
[http://dx.doi.org/10.1007/s10562-017-2156-8.]
(d)Tripathi, B.P.; Mishra, A.; Rai, P.; Pandey, Y.K.; Srivastava, M.; Yadav, S.; Singh, J. Singh, J. A green and clean pathway: One pot, multicomponent, and visible light assisted synthesis of pyrano[2,3-c]pyrazoles under catalystfree and solvent-free conditions. New J. Chem.,, 2017, 4, 11148-11154.Available at.
[http://dx.doi.org/10.1039/C7NJ01688C.]
(e)Mishra, A.; Rai, P.; Pandey, Y.K.; Singh, J. Singh, J. An Eco-Sustainable synthetic approach for 4,5-Dihydro-1H-pyrazoles via DBU catalysis in micellar medium. ChemistrySelect,, 2017, 2, 10979-10983.Available at.
[http://dx.doi.org/10.1002/slct.201702400.]
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