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Molecules 2010, 15(9), 6619-6629; doi:10.3390/molecules15096619
Article

Green One Pot Solvent-Free Synthesis of Pyrano[2,3-c]-Pyrazoles and Pyrazolo[1,5-a]Pyrimidines

1,* , 2, 1 and 1
1 Chemistry Department, Faculty of Science, University of Kuwait, P.O. Box 5969, Safat, 13060 Kuwait 2 Chemistry Department, Faculty of Science, Cairo University, Giza, 12613, Egypt
* Author to whom correspondence should be addressed.
Received: 26 July 2010 / Revised: 13 August 2010 / Accepted: 26 August 2010 / Published: 20 September 2010
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Abstract

Pyrano[2,3-c]pyrazoles are obtained via mixing ethyl acetoacetate, hydrazine hydrate, aldehydes or ketones and malononitrile in the absence of solvent. These same products were also obtained by reacting arylidenemalononitriles 3 with 3-methyl-2-pyrazolin-5-ones. NOE difference experiments confirmed that these products exist solely in the 2H form. Similar treatments of 3-amino-2-pyrazolin-5-one with arylidene-malononitrile afforded adduct 6. Similarly mixing ethyl cyanoacetate, hydrazine hydrate, aldehydes, with malononitrile gave the same product 6. A novel synthesis of 4-oxo-4H-pyrano[2,3-c]pyrazole (8) could be achieved via reacting 3-methyl-2-pyrazolin-5-one with a mixture of cyanoacetic acid and acetic anhydride. Similar treatment of 3-aminopyrazole 11 with the benzylidene-malononitrile produced the pyrazolo[2,3-a]pyrimidines 12a,b.
Keywords: pyranopyrazole; multi-component synthesis; aminopyrazolinone; pyrazolo[1,5-a]pyrimidine; cyanoacetic acetic anhydride; NOE difference experiments pyranopyrazole; multi-component synthesis; aminopyrazolinone; pyrazolo[1,5-a]pyrimidine; cyanoacetic acetic anhydride; NOE difference experiments
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Al-Matar, H.M.; Khalil, K.D.; Adam, A.Y.; Elnagdi, M.H. Green One Pot Solvent-Free Synthesis of Pyrano[2,3-c]-Pyrazoles and Pyrazolo[1,5-a]Pyrimidines. Molecules 2010, 15, 6619-6629.

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