Chemistry Department, Faculty of Science, University of Kuwait, Safat, Kuwait.
Molecules. 2010 Sep 20;15(9):6619-29. doi: 10.3390/molecules15096619.
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.
吡喃并[2,3-c]吡唑是通过在无溶剂的条件下混合乙酰乙酸乙酯、水合肼、醛或酮和丙二腈来获得的。这些相同的产物也可以通过反应芳亚甲基丙二腈 3 与 3-甲基-2-吡唑啉-5-酮来获得。NOE 差示实验证实这些产物仅以 2H 形式存在。用芳亚甲基丙二腈对 3-氨基-2-吡唑啉-5-酮进行类似的处理得到加合物 6。同样，将氰基乙酸乙酯、水合肼、醛与丙二腈混合也得到相同的产物 6。通过将 3-甲基-2-吡唑啉-5-酮与氰基乙酸和乙酸酐的混合物反应，可以实现 4-氧代-4H-吡喃并[2,3-c]吡唑（8）的新合成。用苄亚甲基丙二腈对 3-氨基吡唑 11 进行类似的处理得到吡唑并[2,3-a]嘧啶 12a,b。
