Synthesis of N-Substituted 4-Quinolones via Palladium-Catalyzed Enantioselective C-N Coupling and Base-Promoted Reactions

A highly efficient palladium-catalyzed asymmetric synthesis of N-substituted 4-quinolones was developed via C-N coupling reaction. Various chiral quinolones were readily obtained with desirable enantioselectivity (up to 95% ee) and excellent yield (up to 99%), enabled by a simple system of palladium acetate and chiral ferrocene bisphosphine as auxiliary ligand. The corresponding racemic derivatives can also be synthesized by a transition metal-free strategy of potassium hydroxide in DMSO. The influence of temperature on the configurational stability of these C-N axially chiral compounds was also investigated. The efficient functionalization at 3-position further expands the application range of this synthetic technique.

Automated summary

A highly efficient method for the asymmetric synthesis of N-substituted 4-quinolones through C-N coupling reaction was developed using palladium catalysis. Various chiral quinolones with high enantioselectivity (up to 95% ee) and excellent yield (up to 99%) were easily obtained using palladium acetate and chiral ferrocene bisphosphine as auxiliary ligand. Racemic derivatives could also be synthesized using a transition metal-free strategy with potassium hydroxide in DMSO. The influence of temperature on the configurational stability of these C-N axially chiral compounds was also investigated. The efficient functionalization at 3-position further expands the application range of this synthetic technique.