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