The isomerization of A to B resulted in a decrease bond order of C­N bond and C­O bond, from 1.724 to 1.457 and from 1.869 to 1.663, and an increase bond order of N­N bond and N­C bond, from 1.067 to 1.1.183 and from 0.923 to 1.075. However, the bond patterns are overall similar with A. From B to C, the most significant bond order change associate with the decrease of the C­O bond order, i.e. from 1.663 to 1.274. These bond order changes indicate the isomerization and the combination of Cu(OTf)2 indeed have significant influences on the electronic structures of the reactants.
Minimum­Energy Structures of Cu(OTf)2 Catalyzed [3+2] Cycloaddition