Diverse C(sp3)–H functionalizations through electrochemical benzylic oxygenation

Abstract

Despite significant advances in C(sp³)–H bond functionalization, the development of methods that are site-selective and capable of diverse bond formation remains a challenge. In addition, the preparation of olefins from aliphatics through cleavage of vicinal C(sp³)–H bonds remains difficult due to a lack of stereoselectivity and over-oxidation. To address these challenges, we have developed a transition metal catalyst- and external oxidant-free electrochemical C(sp³)–H oxygenation platform that enables highly stereoselective synthesis of aryl alkenes and diverse benzylic functionalizations to form various C–C and C–heteroatom bonds. This method involves site-selective benzylic C(sp³)–H trifluoroacetoxylation followed by elimination or substitution with diverse carbon- or heteroatom-based nucleophiles to form functionalized products. The utility of this protocol is further demonstrated by the desaturation of methyl dehydroabietate at the decagram scale and transformations of the resulting alkene. This study provides a platform for the diversity-oriented functionalization of both simple alkyl arenes and complex molecules.