Solvent-free, one-pot synthesis and biological evaluation of some new dipyrazolo [3,4-b:4',3'-e]pyranylquinolones and their precursors

One-pot synthesis of 24 new compounds, belonging to three families; dipyrazolo[3,4-b:4',3'-e]pyranylquinolones 7a-h and its precursors (pyrazolonylidene)methylquinolones 5a-h and 4,4'-[(quinolinyl)methylene]bispyrazols 6a-h, 8 from each, has been achieved in the presence of catalyst tetrabutylammonium hydrogen sulfate (TBA-HS) in solvent-free conditions. In addition to assuring chromatography-free product isolation, this method had also allowed the reaction to proceed in a regio-selective manner provided the temperature and amount of pyrazolone are varied. At 100 A degrees C, while 1:1 mixture of aldehyde 3 and pyrazolone 4 underwent Knoevenagel condensation, same reactants taken in ratio of 1:2 mainly domino/Knoevenagel-Michael reaction. At 120 A degrees C, however, the domino/Knoevenagel-Michael-adducts converted into cyclized product, highlighting a new domino/Knoevenagel-Michael-cyclization synthetic sequence. The structure of all heterocycles has been confirmed by mass, IR and NMR spectral data. Based on 2D NMR NOESY experiment, it was also confirmed that the formation of only 'Z' configuration of Knoevenagel alkene took place in the transformation. All are good antitubercular agents as they were found to be active against M. tuberculosis H37RV, in addition to being found active against three Gram-positive (Streptococcus pneumoniae, Clostridium tetani, Bacillus subtilis) and three Gram-negative (Salmonella typhi, Vibrio cholerae, Escherichia coli) bacteria, respectively.