Due to biological and medicinal properties of pyranopyrazoles, synthesis of these bioactive heterocycles has attracted the interest of medicinal and organic chemists. This review focuses on the recent developments in multicomponent synthesis of pyranopyrazole and spiroconjugated pyranopyrazole systems. The present review describes the literature reports for the period 2005 to 2018. These reported approaches were performed in the classical and nonclassical conditions, particularly recent reports includes protocols under a green condition such as using catalyst, green solvents, and solvent-free conditions. ARTICLE HISTORY

Several N-acyl-2-benzoylaziridines were prepared conveniently in good to high yields (71-93%) and used in the preparation of 5-benzoyloxazolines (76-91%) by a regio-and stereo-controlled reaction in the presence of NaI as an efficient catalyst under microwave irradiation in short reaction times (5-10 mins). The structure of the regioisomeric product was confirmed by X-ray analysis.

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The one-pot domino Knoevenagel-type condensation/Michael reaction of aromatic, heteroaromatic and aliphatic aldehydes with 4-hydroxycoumarin in aqueous media in the presence of ruthenium salt as homogeneous catalyst was investigated. It was found that 5 mol% of RuCl3.nH2O catalyzes biscoumarin synthesis in high yields (70-95%) under optimised, mild, green and environmentally benign reaction conditions in short times (25-35min)

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Fused polycyclic 4-aryl-3-methyl-4,7-dihydro-1H-pyrazolo[3,4-b]pyridines were obtained in a three-component regioselective reaction of 5-amino-3-methyl-1H-pyrazole, 2H-indene-1,3-dione and arylaldehydes in ethanol under ultrasound irradiation. This rapid method produced the products in short reaction times (4-5min) and excellent yields (88-97%).

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