Electrochemical and yeast-catalysed ring-opening of isoxazoles in the synthesis of analogues of the herbicide Grasp ®
作者:Christopher J. Easton、Graham A. Heath、C. Merrîcc M. Hughes、Connie K. Y. Lee、G. Paul Savage、Gregory W. Simpson、Edward R. T. Tiekink、George J. Vuckovic、Richard D. Webster
DOI:10.1039/b008081k
日期:——
Isoxazoles substituted with an electron-withdrawing group at the 4-position undergo electrochemical and yeast-catalysed N–O bond cleavage. The electrolysis is much more efficient and, with acyl- and alkoxycarbonyl-substituted isoxazoles, it affords the enolised dicarbonylimine functionality characteristic of the herbicide Grasp®. Regioisomeric 4- and 5-substituted isoxazoles are accessible through nitrile oxide cycloaddition chemistry, using halogen as a steric auxiliary to control the regiochemistry of reaction. Crystal data for compounds 11 and 19b are presented.
Molecular Sieve (MS 4A) Promoted Cyclocondensation of Hindered, Aromatic Nitrile Oxides and Cyclic Diketones under Mild Conditions
作者:Keisuke Suzuki、Tomoo Matsuura、Jeffrey W. Bode、Yoshifumi Hachisu
DOI:10.1055/s-2003-41436
日期:——
Molecular sieves (MS 4A) serve as efficient promoters for the cyclocondensation of stable, hindered nitrile oxides and a variety of cyclic diketones to afford fused isoxazoles in good yield. The operational simplicity and remarkably mild reaction conditions compliment our amine-promoted cyclocondensation conditions and demonstrate broad substrate scope.