Light-driven transition-metal-free direct decarbonylation of unstrained diaryl ketones via a dual C-C bond cleavage.

Abstract

The cleavage and formation of carbon-carbon bonds have emerged as powerful tools for structural modifications in organic synthesis. Although transition-metal-catalyzed decarbonylation of unstrained diaryl ketones provides a viable protocol to construct biaryl structures, the use of expensive catalyst and high temperature (>140 ^oC) have greatly limited their universal applicability. Moreover, the direct activation of two inert C - C bonds in diaryl ketones without the assistance of metal catalyst has been a great challenge due to the inherent stability of C - C bonds (nonpolar, thermo-dynamically stable, and kinetically inert). Here we report an efficient light-driven transition-metal-free strategy for decarbonylation of unstrained diaryl ketones to construct biaryl compounds through dual inert C - C bonds cleavage. This reaction featured mild reaction conditions, easy-to-handle reactants and reagents, and excellent functional groups tolerance. The mechanistic investigation and DFT calculation suggest that this strategy proceeds through the formation of dioxy radical intermediate via a single-electron-transfer (SET) process between photo-excited diaryl ketone and DBU mediated by DMSO, followed by removal of CO₂ to construct biaryl compounds.