Synthesis of Redshifted Azobenzene Photoswitches by Late-Stage Functionalization

David B. Konrad, James A. Frank, Dirk Trauner

Research output: Contribution to journalArticlepeer-review


Azobenzenes are versatile photoswitches that can be cycled between their trans- and cis-configuration with light. The wavelengths required for this isomerization are substantially shifted from the UV to the visible range through tetra-ortho-chlorination. These halogenated azobenzenes display unique photoswitching characteristics, but their syntheses remain limited and inefficient. A new general method for the synthesis of tetra-ortho-chloro azobenzenes has been developed, which relies on direct palladium(II)-catalyzed C-H activation of pre-existing standard azobenzenes. This late-stage functionalization has a broad substrate scope and can be used to create a variety of useful building blocks for the construction of more elaborate redshifted photopharmaceuticals. This method is used to prepare red-AzCA-4, a photoswitchable vanilloid that enables optical control of the cation channel TRPV1 with visible light.

Original languageEnglish (US)
Pages (from-to)4364-4368
Number of pages5
JournalChemistry - A European Journal
Issue number13
StatePublished - Mar 18 2016


  • C-H activation
  • azobenzene
  • halogenation
  • ion channels
  • photopharmacology

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry


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