Efficient synthesis of diversely substituted pyrazolo[1,5-a]pyrimidine derivatives promoted by ultrasound irradiation in water and their antibacterial activities

Abstract

A green synthetic route leading to the discovery of a series of diversely substituted pyrazolo[1,5-a]pyrimidines, having CO₂Et group embedded at position-2 has been unraveled in this article. A series of formylated active proton compounds that were chosen to react with a carboxylate substituted-3-aminopyrazole under ultrasonic irradiation in the presence of a mild acid as a catalyst and aqueous ethanol medium afforded the desired products. The molecular structures of all these synthesized compounds were established by their spectral and analytical data. A model molecule 3d, subjected to single-crystal X-ray crystallography analysis further confirms their molecular structure. The crystal crystallized to a monoclinic cell with P2₁/c space group, a = 7.468 (5) Å, b = 27.908 (17) Å, c = 7.232 (4) Å, β = 104.291 (7)^o, V =1460.7(15) ų, Z = 4, μ(MoKα) = 0.096 mm^-1, D_calc = 1.352 Mg/m³ 16667 measured reflection (5.63 ≤ 2Θ ≤ 57.57°), 3720 unique (R_int = 0.0965, R_sigma = 0.0945) which were used in all calculations. The final R₁ was 0.0750 (I > 2σ(I)) and wR₂ was 0.2226 (all data). These compounds were further explored for their antibacterial potential, and a few of them have exhibited encouraging results.