Download PDF
Synfacts 2005(2): 0202-0202  
DOI: 10.1055/s-2005-916057
Synthesis of Heterocycles
© Georg Thieme Verlag Stuttgart · New York

Isoxazole Boronic Esters

Contributor(s): Victor Snieckus, Till Vogel
J. E. Moore, M. W. Davis, K. M. Goodenough, R. A. J. Wybrow, M. York, C. N. Johnson, J. P. A. Harrity*
University of Sheffield, UK, and Organon Laboratories Ltd, Newhouse, UK, and GlaxoSmithKline, Essex, UK
Further Information

Publication History

Publication Date:
25 October 2005 (online)

    Permissions and Reprints

Significance

Organoboron reagents are current popular synthetic intermediates especially for C-C and C-N bond forming methodologies, e.g. the Suzuki-Miyaura reaction. While aromatic boronic acids and their derivatives are usually conveniently prepared by Li- or Mg-B exchange, the corresponding heteroaromatic boronic acids are difficult to generate and suffer from instability problems. The present report provides a route to isoxazole boronic esters by [3+2] cycloaddition of nitrile oxides with alkynyl boropinacolates. The reaction proceeds in low to good yields and excellent regioselectivities (except for R2 = H); even haloisoxazoles (R1 = Br, Cl) are obtained in 40-69% yield.