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Molecules 2011, 16(8), 7081-7096; doi:10.3390/molecules16087081
Article

Synthesis and Electrophilic Substitutions of Novel Pyrazolo[1,5-c]-1,2,4-triazolo[4,3-a]pyrimidines

Chemistry Department, Faculty of Science, Alexandria University, Ibrahimia P.O. Box 426, Alexandria 21321, Egypt
Received: 30 June 2011 / Revised: 1 August 2011 / Accepted: 4 August 2011 / Published: 18 August 2011
(This article belongs to the Special Issue Heterocycles)
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Abstract

5-Aryl-7-hydrazino-2-phenylpyrazolo[1,5-c]pyrimidines 1 were used as precursors for the preparation of a new series of 5-aryl-8-phenylpyrazolo[1,5-c]-1,2,4- triazolo[4,3-a]pyrimidines 2. The reactions of 2 with certain electrophilic reagents gave the respective 6-substituted derivatives 3-5 rather than the 7-isomeric products. Formylation of the key compounds 1 with ethyl formate yielded the formyl derivatives 6. Furthermore, boiling of compounds 1 with acetic acid afforded 7-acetylhydrazino-5-aryl-2-phenylpyrazolo[1,5-c]pyrimidines 7. Bromination of 7 yielded the dibromo- derivatives 8, while their iodination and nitration gave the monosubstituted derivatives 9 and 10, respectively. Also, treatment of 1 with boiling acetic anhydride yielded the triacetyl derivatives 11. The structure of synthesized products was confirmed by elemental analyses, IR, 1H NMR and MS spectra.
Keywords: pyrazolo[1,5-c]-1,2,4-triazolo[4,3-a]pyrimidines; synthesis; electrophilic substitution reactions; dehydrative cyclization pyrazolo[1,5-c]-1,2,4-triazolo[4,3-a]pyrimidines; synthesis; electrophilic substitution reactions; dehydrative cyclization
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).
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Atta, K.F. Synthesis and Electrophilic Substitutions of Novel Pyrazolo[1,5-c]-1,2,4-triazolo[4,3-a]pyrimidines. Molecules 2011, 16, 7081-7096.

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