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Communication | Special issue | Vol 7, No. 2, 1977, pp.793-799
Published online, 1st January, 1970
DOI: 10.3987/S-1977-02-0793
Regioselectivity of Nitrile Oxide Cycloadditions to Electron-Deficient Dipolarophiles

K. N. Houk,* Yau-Min Chang, Robert W. Strozier, and Pierluigi Caramella

*Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803-1804, U.S.A.


Nitrile oxides give predominantly 5-substituted isoxazolines even with very electron-deficient alkene dipolarophiles, but very electron-deficient alkyne dipolarophiles give substantial amounts of 4-substituted isoxazoles. The contrast between nitrones and nitrile oxides, and between alkenes and alkynes, can be explained on the basis of orbital energies and changes in orbital energies upon molecular distortions in the cycloaddition transition States.