An efficient One-Pot synthesis of NaOCl mediated pyrazolopyrimidine derivatives

The discovery and success of sildenafil, widely recognized as Viagra™, represented a major progress in the treatment of erectile dysfunction (ED). Numerous approaches for synthesis of the Pyrazolo[4,3-d]pyrimidine-7-one ring have reported in the literature. However, those methods have several drawbacks, including high temperatures, low yields, the use of hazardous materials, specific oxidation protocols, long reaction times, multiple reaction steps, and expensive catalysts. To overcome these limitations, we present a simple, catalyst-free, and cost-effective one-pot synthesis of pyrazolopyrimidine derivatives with a high yield and lower reaction time using the inorganic reagent i.e., sodium hypochlorite (NaOCl). The reaction uses easily available starting materials such as 4- amino-1-methyl-3-propylpyrazole-5-carboxamide and aldehyde derivatives under moderate conditions, providing a greener alternative to typical multi-step synthesis techniques. Detailed optimization studies to afford pyrazolopyrimidine derivatives ( 6a-6o ) show that NaOCl is a strong oxidizing agent that promotes cyclization and functionalization processes. Structures of synthesized compounds were confirmed by 1H NMR, 13 C NMR and HR-MS techniques.