Room‐Temperature Copper‐Catalyzed Etherification of Aryl Bromides
摘要:
We disclose the development of a Cu‐catalyzed C−O coupling method utilizing a new N1,N2‐diarylbenzene‐1,2‐diamine ligand, L8. Under optimized reaction conditions, structurally diverse aryl and heteroaryl bromides underwent efficient coupling with a variety of alcohols at room temperature using an L8‐based catalyst. Notably, the L8‐derived catalyst exhibited enhanced activity when compared to the L4‐based system previously disclosed for C−N coupling, namely the ability to functionalize aryl bromides containing acidic functional groups. Mechanistic studies demonstrate that C−O coupling utilizing L8 ⋅ Cu involves rate‐limiting alkoxide transmetallation, resulting in a mechanism of C−O bond formation that is distinct from previously described Pd‐, Cu‐, or Ni‐based systems. This lower energy pathway leads to rapid C−O bond formation; a 7‐fold increase relative to what is seen with other ligands. The results presented in this report overcome limitations in previously described C−O coupling methods and introduce a new ligand that we anticipate may be useful in other Cu‐catalyzed C‐heteroatom bond‐forming reactions.
Novel oxadiazole compounds, pharmaceutical compositions containing such compounds and the use of those compounds or compositions as agonists or antagonists of the S1P family of G protein-coupled receptors for treating diseases associated with modulation of S1P family receptor activity, in particular by affording a beneficial immunosuppressive effect are disclosed.