Reactivity and mechanistic insight into the cross coupling reaction between isochromans and β-keto esters through C-H bond activation under visible light irradiation

The visible light catalytic cross coupling reaction from two different C-H bonds provides an efficient protocol for C-H bond activation and C-C bond construction. The application of the oxidative photoredox strategy to couple C-H bonds next to an oxygen atom with other C-H bonds is more challenging because of the more positive oxidation potential of ethers than that of amines. Here, we take advantage of organic dye 9-mesityl-10-methylacridinium perchlorate (Acr(+)-Mes ClO4-) as the photosensitizer and BrCCl3 as the terminal oxidant to achieve the addition of beta-keto esters to oxonium species, directly generated from isochromans, leading to the formation of alkylation products in the alpha-position of an oxygen atom under visible light irradiation.