An efficient procedure for the syntheses of pyrazolo[1,5-a]pyrimidines through reactions of 1,2-allenic ketones with aminopyrazoles under extremely mild conditions without using any catalyst or promoter has been developed. The reactions showed excellent regio-selectivity with all the allenic ketone substrates except for those bearing an alkyl group at the internal position of the allene moiety. The reason behind this regio-selectivity dissimilarity has been explored with the aid of the B3LYP/6-31G* level of density functional theory. Moreover, this novel procedure has been successfully applied in the preparation of nucleoside-pyrazolo[1,5-a]pyrimidine chimeras with potent antiviral activities.
在极其温和的条件下,不使用任何催化剂或
促进剂,通过 1,2-异烯酮与
氨基
吡唑的反应合成
吡唑并[1,5-a]
嘧啶的高效程序已经开发出来。除了那些在烯酮分子内部位置带有烷基的底物外,该反应对所有烯酮底物都显示出极好的区域选择性。借助密度泛函理论的 B3LYP/6-31G*
水平,我们探索了这种区域选择性差异背后的原因。此外,这种新程序已成功应用于制备具有强效抗病毒活性的核苷-
吡唑并[1,5-a]
嘧啶嵌合体。