A CSA-catalyzed strategy for constructing 1H-pyrazolo[4,3-f]quinoline-8-carboxamide scaffolds as antimicrobial agents.

An environmentally sustainable one-pot methodology has been established for the synthesis of 1H-pyrazolo[4,3-f]quinoline-8-carboxamide derivatives 4(a-n) using camphorsulfonic acid (20 mol%) as a natural-product-based organocatalyst. The reaction, performed in refluxing ethanol using acetoacetanilide, aromatic aldehydes, and 5-aminoindazole, affords the desired products in excellent yields (up to 90%). The green credentials of the protocol are supported by low E-factor values (0.198-0.455), high atom economy (93.19%), effective atom economy (83.56%), and carbon efficiency (237.81%). Biological screening indicates that compounds 4i and 4k possess strong antibacterial activity, while compounds 4c, 4d, and 4n exhibit enhanced antifungal activity relative to tetracycline and fluconazole. In addition, compounds 4d, 4i, and 4j demonstrate potent anticancer activity against the MCF-7, HepG2, and SiHa cell lines.