Abstract
We report a modular approach toward novel arylazotriazole photoswitches and their photophysical characterization. Addition of lithiated TIPS-acetylene to aryldiazonium tetrafluoroborate salts gives a wide range of azoacetylenes, constituting an underexplored class of stable intermediates. In situ desilylation transiently leads to terminal arylazoacetylenes that undergo copper-catalyzed cycloadditions (CuAAC) with a diverse collection of organoazides. These include complex molecules derived from natural products or drugs, such as colchicine, taxol, tamiflu, and arachidonic acid. The arylazotriazoles display near-quantitative photoisomerization and long thermal Z-half-lives. Using the method, we introduce for the first time the design and synthesis of a diacetylene platform. It permits implementation of consecutive and diversity-oriented approaches linking two different conjugants to independently addressable acetylenes within a common photoswitchable azotriazole. This is showcased in the synthesis of several photoswitchable conjugates, with potential applications as photoPROTACs and biotin conjugates.
Highlights
We report a modular approach toward novel arylazotriazole photoswitches and their photophysical characterization
Photoswitches are widely applied in various modern settings, methods for their synthesis largely rely on traditional approaches (Scheme 1A)
Given the success of arylazopyrazoles with near-quantitative photoisomerization and high bistability pioneered by Fuchter,[6,7] we envisioned that 1,4-substituted arylazotriazoles 4 could possess beneficial photophysical properties (Scheme 1B).[8]
Summary
Authors Patrick Pfaff − Laboratorium für Organische Chemie, ETH Zürich, D-CHAB, 8093 Zürich, Switzerland; orcid.org/ 0000-0002-9761-2497 Felix Anderl − Laboratorium für Organische Chemie, ETH Zürich, D-CHAB, 8093 Zürich, Switzerland Moritz Fink − Laboratorium für Organische Chemie, ETH Zürich, D-CHAB, 8093 Zürich, Switzerland Moritz Balkenhohl − Laboratorium für Organische Chemie, ETH Zürich, D-CHAB, 8093 Zürich, Switzerland. P.P. is an awardee of the Scholarship Fund of the Swiss Chemical Industry (SSCI). F.A. thanks the FWF for an Erwin Schrödinger Fellowship for post-doctoral support (Project J4461); M.B. thanks the Deutsche Forschungsgemeinschaft (DFG) for a postdoctoral fellowship. Notes The authors declare no competing financial interest. During the final stages of this work we became aware of work by Prof.
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