Synchronized biphotonic process triggering C-C coupling catalytic reactions

Activation of aryl(Ar)-halides for C-C coupling catalytic reactions using visible light has become one of the most challenging tasks in organic synthesis since it offers effective and safer alternatives to traditional dehalogenation protocols. The insufficient energy provided by visible light to cleave such strong C-H alogen bonds certainly makes necessary the development of new protocols to overcome this limitation. We report here the application of photon upconversion (UC) technology based on triplet-triplet annihilation (TTA) to a C-C coupling catalytic reaction, a possibility that has not been investigated to date. This synchronized biphotonic process (TTA-UC) activates successfully Ar-halides with visible light. Based on product analysis and spectroscopic experiments, a cascade process combining photophysical and photochemical steps is proposed for the mechanism rationalization. Visible light, ambient temperature and pressure, low-loading metal-free photocatalysts and no additives make this protocol very attractive for applications to the synthesis of fine chemical building blocks, pharmaceuticals, agrochemicals or new materials.