Exo/Endo Stereoselectivity in 1,3-Dipolar Cycloaddition of Trifluoroacetonitrile Oxide and -nitrilimine with Bicyclic Olefins

Trifluoroacetonitrile oxide and N-phenyl-C-(trifluoromethyl)nitrilimine cycloadded with norbornenes, resulting in the exclusive formation of the exo-adducts, while the concomitant formation of the endo-adducts was observed in their cycloadditions with norbornadienes. The nitrile oxide was subjected to the cycloaddition with 2,3-disubstituted norbornadienes to evaluate the effect of the substituents on the exo/endo stereoselectivity. The electron-withdrawing substituents tend to favor the formation of the exo-adducts.