A facile, catalyst-free synthesis of new polycyclic pyrrolo[1,2-b]pyrazolone derivatives

A convenient and efficient procedure has been developed for the synthesis of a new ring system, pyrrolo[1,2-b]pyrazolone, via two-component coupling reaction followed by base mediated intramolecular cyclization. Single-pot synthesis replacing the two step process has also been successfully carried out. A series of polycyclic pyrrolo[1,2-b]pyrazolone derivatives have been obtained by employing the procedure along with some fused pyrrol-1-ylamine system. The products were formed very rapidly in catalyst free condition in a good yield (up to 75%) and also it had tolerance to a wide scope of substrates.