The reaction of nitrile oxide-quinone cycloadducts. III. Reinvestigation of the base-induced isomerization of the 1:1 -C=C-adducts of aromatic nitrile oxides with 2,5-and 2,6-dialkyl-substituted p-benzoquinones

Article abstract of DOI:10.1246/bcsj.72.2549

The structure of the product obtained by the base, induced isomerization of the 1,3-dipolar cycloadduct of 2,5-di-t-butyl-p-benzoquinone with 2,6- dichlorobenzonitrile oxide was determined by X-ray analysis. The t-butyl group at the bridgehead position of the 1,3-dipolar cycloadduct migrated to the neighboring carbonyl carbon atom. This base-induced rearrangement took place with a bulky group, i.e., Et, i-Pr, t-Bu, and Bn at the bridgehead position of nitrile oxide-quinone cycloadducts in an alcoholic media. The driving force of this reaction is considered to be due to stabilization by aromatization from isoxazoline derivatives to isoxazole-fused p-quinol derivatives.