Variable Activity of Reagents with C=C and N=N Bonds in Cycloaddition Reactions

Data on rates and enthalpies of the reactions of quadricyclane (4) and diadamantylidene (5) with N-phenylmaleimide (1), 4-phenyl-1,2,4-triazoline-3,5-dione (2), and tetracyanoethylene (3) are obtained for the first time. Reagent 2 with the N=N reaction center is found to be six orders of magnitude more active than its structural analog 1. A strong π-acceptor 3 is 370 times more active than reagent 2 in the reaction with a strong π-donor substrate 4 but is less active than reagent 2 in many [4π + 2π], [2π + 2π + 2π], and [2π + 2π] cycloaddition reactions, and, especially, in ene reactions. The possible causes of the strong difference and variable activity of compounds 1–3 with C=C and N=N bonds are discussed.