Copper‐Catalyzed Synthesis of Substituted 4‐Quinolones using Water as a Benign Reaction Media: Application for the Construction of Oxolinic Acid and BQCA.

A copper‐catalyzed three‐component synthetic method has been developed for the synthesis of substituted 4‐quinolone derivatives from substituted 3‐(2‐halophenyl)‐3‐oxopropane, aldehydes and aq. NH3 using water as an environmentally benign reaction media. Moreover, the synthetic utility of the obtained products has been successfully applied for the synthesis of available oxolinic acid and BQCA drugs. The key features of this approach include commercially available starting materials, broad scope, and moderate to good reaction yields. Reaction with formaldehyde, and other functionalities such as −CN, −NO2, −SO2Ar, and −COAr were also successful. In addition, reaction with heterocyclic compounds such as 3‐(3‐bromothiophen‐2‐yl)‐3‐oxopropanenitrile proceeded smoothly to afford tetrahydrothieno[3,2‐b]pyridine‐6‐carbonitrile analogues. The practicality of the designed protocol was confirmed by gram scale synthesis of two derivatives. [ABSTRACT FROM AUTHOR]