Easily attachable and detachable ortho-directing agent for arylboronic acids in ruthenium-catalyzed aromatic C-H silylation

  • J Am Chem Soc. 2009 Jun 10;131(22):7502-3. doi: 10.1021/ja902314v.
Hideki Ihara  1 ,  Michinori Suginome
Affiliations
  • 1. Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
PMID: 19435323 DOI: 10.1021/ja902314v
Abstract

o-C-H silylation of arylboronic acids has been achieved using 2-pyrazol-5-ylaniline as an ortho-directing agent, which was temporarily attached to the boronyl group via Ru-catalyzed silylation with hydrosilanes. Condensation products of arylboronic acids with 2-pyrazol-5-ylaniline were prepared in situ and subjected to reaction with triorganosilanes in the presence of RuH(2)(CO)(PPh(3))(3) at 135 degrees C. Regioselective silylation at their ortho-positions proceeded in good yields for phenylboronic acids bearing para-substituents such as chloro, fluoro, methyl, methoxy, and trifluoromethyl groups. p-Methoxycarbonyl-substituted phenylboronic acid provided the corresponding silylated product in moderate yield. m-Tolyl- and 2-naphthylboronic acids underwent silylation selectively at the less sterically hindered ortho-positions. The silylated products were utilized in Suzuki-Miyaura coupling, followed either by iodination with ICl or by Tamao oxidation to furnish iodine- or hydroxy-substituted biaryls.

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