Green access to novel spiro pyranopyrazole derivatives

A catalyst-free multicomponent reaction (MCR) capable of affording a wide range of novel spiro pyranopyrazole derivatives from pyrazolone in situ formed from acetylenic esters with hydrazine hydrate at room temperature with isatin and malononitrile is reported. A plausible mechanism is suggested. Catalyst-free conditions along with green solvent system make the process ecofriendly as well as economical. Simple reaction conditions and easy work-up procedure that resulted into simple isolation and purification of products by non-chromatographic methods, that is, by simple recrystallization from methanol as well as novelty are the significant advantages of the present protocol.