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Arylazoindazole Photoswitches: Facile Synthesis and Functionalization via SNAr Substitution

Travieso-Puente, Raquel, Budzak, Simon, Chen, Juan, Stacko, Peter, Jastrzebski, Johann T. B. H., Jacquemin, Denis, Otten, Edwin
Journal of the American Chemical Society 2017 v.139 no.9 pp. 3328-3331
ambient temperature, cis-trans isomers, half life, isomerization
A straightforward synthetic route to arylazoindazoles via nucleophilic aromatic substitution is presented. Upon deprotonation of the NH group, a C₆F₅-substituted formazan undergoes facile cyclization as a result of intermolecular nucleophilic substitution (SNAr). This new class of azo photoswitches containing an indazole five-membered heterocycle shows photochemical isomerization with high fatigue resistance. In addition, the Z-isomers have long thermal half-lives in the dark of up to several days at room temperature. The fluorinated indazole group offers a handle for further functionalization and tuning of its properties, as it is shown to be susceptible to a subsequent, highly selective nucleophilic displacement reaction.