Structure of norbornene-fused 3,1-oxazine double cycloadducts.

Pentacyclic isoxazolines were obtained by the cycloaddition of benzonitrile oxide to norbornene-azetidinone-fused 3,1-oxazines. The constitutions of two of the isomers obtained, and the configurations and conformations of all products, were determined by means of 1 H and 13 C NMR spectroscopy and DNOE experiments.