An Alternative Regioselective Approach for the Synthesis of Highly Functionalized Derivatives of Pyrazolo[5,1‐ bb ]purine Scaffold

摘要

> A straightforward approach for the regioselective synthesis of highly functionalized pyrazolo[5,1‐ b ]purine from the annulation of 6‐bromo‐3‐cyano‐2‐(ethylthio)‐5‐methyl‐7‐oxo‐6,7‐dihydropyrazolo[1,5‐ a ]pyrimidine with thiourea as a bisnucleophilic reagent under reflux condition in CH ₃ CN in the presence of Et ₃ N has been developed. The N ‐alkylation of the synthesis compound was also accomplished. The true regioisomer was determined by 2 D‐NOESY NMR spectroscopy, as well.