A Three‐Component Domino Reaction Enabled by Phase‐Transfer Catalysis for the Assembly of 3‐Thioquinoline‐2,5‐Diones

Abstract

A three‐component phase‐transfer‐catalytic domino reaction involving cyclohexane‐1,3‐dione‐derived enaminones, 5‐alkenyl rhodanines, and haloalkanes has been developed. This protocol produces a wide range of 3‐thioquinoline‐2,5‐diones in yields of 52–81%. The construction of a C−S bond at the C‐3 position of the quinoline‐2,5‐dione framework expands its structural diversity. Studies into the reaction mechanism revealed that the reaction undergoes a conjugate addition, ammonolysis, elimination, and nucleophilic substitution sequence. The synthetic potential of the reaction was demonstrated by the gram‐scale syntheses of representative products. Chloroalkyl chains were installed on the sulfur atoms of most products obtained in this reaction. Diversified product derivatives were obtained by exploiting the favorable leaving nature of chloride moiety.