Design, Synthesis, and Characterization of Tautomeric Quinoline‐4‐Carboxylic Acid–Based Esters, Amides, and Fused Heterocycles

OpenAlex · İngilizce

Quinoline‐4‐carboxylic acid derivatives are widely studied owing to their structural versatility and relevance in pharmaceutical sciences. In this study, 3‐benzoyl‐2‐oxo‐1,2‐dihydroquinoline‐4‐carboxylic acid was synthesized via a solvent‐free reaction between ethyl 3‐oxo‐3‐phenylpropanoate and sodium 2‐(2‐aminophenyl)‐2‐oxoacetate. Two distinct tautomeric forms of the product were identified, offering opportunities for further derivatization. New quinoline ester derivatives were obtained by reacting the open‐form tautomer with various alcohols. The corresponding quinoline amide derivatives were synthesized via the reaction of 3‐benzoyl‐2‐oxo‐1,2‐dihydroquinoline‐4‐carbonyl chloride, obtained by the reaction between 3‐benzoyl‐2‐oxo‐1,2‐dihydroquinoline‐4‐carboxylic acid and SOCl 2 , with ammonia, hydrazine, and various aromatic primary amines. The cyclization of the hydrazine‐derived quinoline amide derivative yielded the pyridazino[4,5‐c]quinoline derivative. Furthermore, a series of novel pyrrolo[3,4‐c]quinoline derivatives were synthesized via Schiff base reactions between various primary amines and the ketone‐containing 3‐benzoyl‐2‐oxo‐1,2‐dihydroquinoline‐4‐carboxylic acid. Hence, a diverse group of quinoline‐4‐carboxylic acid derivatives, including pyridazino, pyrrolo, amide, and ester derivatives, was successfully synthesized using optimized procedures. All synthesized compounds were thoroughly characterized, and their structures were confirmed by infrared spectroscopy, mass spectrometry, and proton and carbon‐13 nuclear magnetic resonance spectroscopy. These findings contribute to the development of structurally novel heterocyclic frameworks and may serve as valuable platforms for future drug discovery and medicinal chemistry applications.