Study On The Synthesis Of Pyrazolopyrimidines And Pyrazoloquinazolines

In this thesis, novel synthetic methods for the preparation of pyrazolopyrimidines and pyrazolo-quinazolines have been developed. It mainly includes the following two parts:1. An efficient procedure for the syntheses of pyrazolo[1,5-a]pyrimidines through reactions of1,2-allenic ketones with aminopyrazoles under extremely mild conditions without using any catalyst orpromoter has been developed. It is worth to be noted that the reactions showed excellent regio-selectivitywith all the allenic ketone substrates except for those bearing an alkyl group at the internal position of theallene moiety. The reason behind this regio-selectivity dissimilarity was elucidated with the aid of theB3LYP/6-31G*level of Density Functional Theory. Moreover, by using the synthetic strategy developedabove, some nucleoside-pyrazolo[1,5-a]pyrimidine chimeras with potent antiviral activities were preparedvia reactions of5-allenyl pyrimidine nucleosides with aminopyrazole.2. A copper-catalyzed tandem reactions of the commercially available2-bromobenzaldehydes or2-bromophenyl alkyl/aryl ketones with5-aminopyrazoles turned out to be an efficient and straightforwardapproach toward pyrazolo[1,5-a]quinazolines. Further studies showed that substrates with differentsubstituents took part in this tandem reaction smoothly to give a series of pyrazolo[1,5-a]quinazolinesefficiently and conveniently.In summary, this thesis demonstrates several facile and efficient procedures for the synthesis ofpyrazolo[1,5-a]pyrimidines and pyrazolo[1,5-a]quinazolines. These novel protocols employ readilyavailable starting materials and show high efficiency, eco-friendly nature and good functional grouptolerance.