Synthesis of Highly Substituted Pyrrolo[1,2‐a]quinoline‐3,5‐diones through Ag(I) Catalyzed Cyclization of 4‐Hydroxyquinolinyl‐2‐ynones

Abstract

AbstractAn efficient synthetic route to access highly substituted pyrrolo[1,2‐a]quinoline‐3,5‐diones in which the core is formed by fusion of quinolone and pyrrolone moieties is discussed. The method involves Ag(I) catalyzed cyclization of 4‐Hydroxyquinolinyl‐2‐ynones which in turn may be accessed from kynurenic acid derivatives through Weinreb amide intermediate, followed by alkyne addition. Studies involving substrates with different substitution pattern revealed that factors increasing the nucleophilicity of quinoline nitrogen or Lewis acid‐coordination of the ynone unit gives high yields in short reaction times. It was possible to execute tandem cyclization‐arylation sequence by using Pd(II) generated by oxidative addition of Pd(0) with aryl iodide as the electrophilic species to get substitution pattern as seen in Discoipyrrole A.