Dichromatic Photocatalytic Substitutions of Aryl Halides with a Small Organic Dye

Photocatalytic bond activations are generally limited by the photon energy and the efficiency of energy and electron transfer processes. Direct two‐photon processes provide sufficient energy but the ultra‐short lifetimes of the excited states prohibit chemical reactions. The commercial dye 9,10‐dicyanoanthracene enabled photocatalytic aromatic substitutions of non‐activated aryl halides. This reaction operates under VIS‐irradiation via sequential photonic, electronic, and photonic activation of the simple organic dye. The resultant highly reducing excited photocatalyst anion readily effected C−H, C−C, C−P, C−S, and C−B bond formations. Detailed synthetic, spectroscopic, and theoretical studies support a biphotonic catalytic mechanism. Two photons to tango: A highly reducing photocatalytic system was developed that involves the sequential combination of photonic, electronic, and photonic activation of 9,10‐dicyanoanthracene, a simple commercial and soluble organic dye. The ultimately formed excited radical anion DCA.−* enables the reductive activation of various aryl bromides and chlorides under mild conditions and the application to hetero‐biaryl cross‐coupling and heteroatom functionalizations. Detailed spectroscopic and theoretical studies support the postulated dichromatic photocatalytic mechanism.