Photocatalytic C−H Amination of Electron-rich Aromatic Hydrocarbons by Carbon Nitride Photocatalysis

Abstract

Construction of C−N bond is a central process in organic synthesis. Typically, it relies on noble-metal catalysts and prefunctionalized substrates, such as aryl halides. Alternative and more appealing method is a direct C−H amination of hydrocarbons that is based on intrinsic reactivity of the in situ generated radical cations, which are more electrophilic compared to their closed-shell precursors. In this work, we employ potassium poly(heptazine imide) (K-PHI), a graphitic carbon nitride semiconductor, to enable C−H amination of electron rich aromatic hydrocarbons with NH3 and pyrazole under oxidative conditions. Screening of oxidants, indicate those molecules that are able to accept not only electrons, but also protons, such as O2, PhNO2 and Ph2S2, mediate the reaction. As such, multisite proton-coupled electron transfer (MS-PCET) from the photocharged state of K-PHI to the acceptor of electrons and protons is the key element in the studied photocatalytic process.