An efficient synthesis of fluorine-containing substituted spiro[piperidine-4,4′-pyrano[3,2-c]quinoline]-3′-carbonitrile by nonconventional methods

‘Solvent-free’ and ‘on-solvent’ multicomponent reaction of isatins, malononitrile, and bicyclic CH-acids: fast and efficient way to medicinal privileged spirooxindole scaffold

“…17,18 Other known methodologies utilize techniques such as microwave irradiation and sonication with heating, which generally result in insufficient yields of spiroindoline-3,4'-pyrano[3,2-c]quinolones. 19,20 In regard to spiroindoline-3,4'-pyrano[3,2c]chromenes, most methods are concerned either with only one or two examples of the synthesis of spiroindoline-3,4'-pyrano[3,2-c]chromenes, 16,[21][22][23][24] or suffer from high temperatures, extremely expensive catalysts [25][26][27] and also long reaction times (of the order of two days). 28 © ARKAT USA, Inc Thus, each of the known procedures for the synthesis of the spiro-oxindole fragments connected with a nitrogen-containing heterocyclic system has its merits; however, a fast and efficient PASE 'solvent-free' and 'onsolvent' method for this process has yet to be developed.…”