Synthesis of 5-Substituted 3-Amino-1H-Pyrazole-4-Carbonitriles as Precursors for Microwave Assisted Regiospecific Syntheses of Pyrazolo[1,5-a]Pyrimidines
作者:Fawzia Al-Qalaf、Faisal Mandani、Mervat Mohammed Abdelkhalik、Abeer Abdulrahman Bassam
DOI:10.3390/molecules14010078
日期:——
A simple route to 3-oxoalkanonitrile 5, aprecursor of the title compounds is described. Reaction of enaminones 2 with hydroxylamine hydrochloride in ethanol yielded aldoximes 3 that were converted readily into 5 in basic medium. This method has been successfully applied with a number of substrates and resulted in excellent yields of the products. Reacting 5 with trichloroacetonitrile afforded 3-amino-2-aroyl-4,4,4-trichloro-2-butenenitriles 6 that condensed with hydrazines to yield 3-amino-1H-pyrazole-4-carbonitrilederivatives 8. Substituted pyrazolo[1,5-a]pyridmidines have been prepared with regioselective condensation reactions of 8 with nonsymmetrical dielectrophiles. The structures of compounds obtained were deduced based on 1H-NMR, 1H-15N HMBC- measurements.
描述了一条简单的合成路线,用于制备标题化合物的前体3-oxoalkanonitrile 5。将enaminones 2与盐酸羟胺在乙醇中反应,生成了aldoximes 3,这些化合物可以在碱性条件下轻易转化为5。这种方法成功应用于多种底物,产生了优良的产率。将5与三氯乙腈反应,得到3-amino-2-aroyl-4,4,4-trichloro-2-butenenitriles 6,进而与肼反应生成3-amino-1H-pyrazole-4-carbonitrile衍生物8。通过与不对称双电电荷体的区位选择性缩合反应,合成了取代的pyrazolo[1,5-a]pyridimidines。根据1H-NMR和1H-15N HMBC测定推导出所获得化合物的结构。