4H-Pyrano[2,3-c]pyrazoles: a review

This review summarizes the synthetic pathways to pyrano [2,3-c]pyrazoles which either have a hydrogen atom, aryl substituent or condensed spiro group at the 4-position. Synthesis focuses on two component or MCR's including three, four and five components. Reaction conditions are variable including a green approach, nanoparticulate catalyst, microwave irradiation, ultrasonic irradiations and other catalysts. Most commonly used reagents are pyrazolones, benzylidenemalononitrile, hydrazines, -ketoesters, malononitrile, aldehydes and ketones. Various substituted phenyl, naphthalene, anthracene, furan, thiophene, indole, tetrahydroquinoline have been incorporated at 4-position while amino and cyano groups at sixth and fifth position respectively and posses diverse biological properties.