Synthesis and Antimicrobial Screening of Pyrimidine Annulated Dihydropyrano[2, 3-c]pyrazole Derivatives

A series of pyrimidine annulated dihydropyrano[2, 3-c]pyrazole derivatives were synthesized and screened for their antimicrobial activity. The precursor, dihydropyrano[2, 3-c]pyrazole was synthesised under catalyst free condition using PEG-400 as reaction medium which facilitated improved yield compared to base catalyzed reaction. Wide scope of substrates, simple workup procedure and high yield even in the absence of catalyst are the major highlights of the protocol. Dihydropyrano[2, 3-c]pyrazoles on condensation with formic acid formed pyrimidine annulated dihydropyrano[2, 3-c]pyrazole derivatives. All the products are characterized using FTIR, $^1H-NMR$ and $^{13}C-NMR$ spectroscopic techniques. The molecules have shown good to moderate activity as antimicrobial agents when compared to the standard drug ciprofloxacin.