Exhaustive catalytic ortho-alkoxylation of azobenzenes: flexible access to functionally diverse yellow-light-responsive photoswitches

We develop the first method for catalytic, exhaustive ortho-alkoxylation of azobenzene photoswitches. Alkoxylation is known to improve the photoswitch properties that control azobenzenes' success in chemical biology or materials sciences: e.g. better completeness of both E→Z and Z→E photoisomerisations, and >100 nm red-shifting of photoresponse. Our method enables straightforward late-stage diversification of photoswitches with interesting functional handles. We showcase four applications, using it to rationally tune lipophilicity, prepare isotopic tracers for metabolism studies, install full water solubility without ionic charges, and efficiently access previously difficult mixed-substituent photoswitches. We also identified a previously unstudied mixed-substituent tetra-ortho-family, difluoro-dialkoxy-azobenzenes, whose photoresponse can outperform previous 'gold standard' tetrafluoro-, dichloro-difluoro-, and tetrachloro-azobenzenes in significant ways. We thus expect that both the scaffolds we showcase and the method we develop will impact broadly on photochemistry and photopharmacology.