Green one pot solvent-free synthesis of pyrano[2,3-c]-pyrazoles and pyrazolo[1,5-a]pyrimidines.
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.
Al-Matar
Hamad M
HM
Chemistry Department, Faculty of Science, University of Kuwait, Safat, Kuwait. h.almatar@ku.edu.kw
Khalil
Khaled D
KD
Adam
Aisha Y
AY
Elnagdi
Mohamed H
MH
D055772:Green Chemistry Technology; D011720:Pyrazoles / Q000138:chemical synthesis*; D011743:Pyrimidines / Q000138:chemical synthesis*
D011720:Pyrazoles; D011743:Pyrimidines