High Throughput Synthesis of Extended Pyrazolo[3,4-d]dihydropyrimidines

Thirteen 5-hetarylaminopyrazoles were synthesized in 62–93% yield through the arylation of 1-isopropyl- and 1-phenyl-5-aminopyrazoles with electrophilic hetarylhalides under optimized conditions. Condensation of 5-hetarylaminopyrazoles with carbonyl compounds facilitated by AcOH or Me3SiCl furnished 23 pyrazolo[3,4-d]dihydropyrimidines in 69–86% yield. The target compounds were isolated through simple crystallization. The scope and limitation of the method are discussed.