1,3-Dipolar Cycloaddition Reactions of 2,4,6-Cycloheptatrien-1-imines with Benzonitrile Oxides Leading to 1,2,4-Oxadiazaspiroundeca-2,6,8,10-tetraenes

Article abstract of DOI:10.1246/bcsj.68.3539

1,3-Dipolar cycloaddition reactions of N-aryl-2,4,6-cycloheptatrien-1-imines with p-substituted benzonitrile oxides afforded <2+3>-type cycloadducts in considerable yields.A study of the substituent effect on the reaction rate revealed that the reactions proceeded through nucleophilic reactions of imines to nitrile oxides.Thermal isomerizations and addition reactions of the adducts showed that the contribution of a valence isomerization between cycloheptatriene and norcaradiene lay to the side of the cycloheptatriene form.A comparison of the UV spectra between the adduct and its derivative, which was reduced by catalytic hydrogenation, implies that the spiroconjugation between cycloheptatriene and a five-membered heterocyclic moiety causes a shift of the equilibrium.