Metal-Free Synthesis of 4-Aryl-2-quinolone Derivatives by Iodine-Mediated Intramolecular C-H Amidation

A metal-free synthesis of a range of 4-aryl-2-quinolone derivatives has been developed which utilizes an iodine-mediated intramolecular C-H amidation of 3,3-diarylacryl amides as the key step. Electron-withdrawing or -donating substituents in either of the aryl rings display marginal influence on the course of the reaction. However, the presence of the diarylalkene moiety has been found to be crucial for the success of the reaction. The reaction proceeds in very good yield and is applicable to a range of substrates. Moreover, the methodology overcomes some of the difficulties associated with metal-mediated approaches such as regio-isomeric product formation, and E-Z isomerization. We propose a mechanism involving the in situ generation of hypoiodous acid as source of positive iodine.