Reactions of electron donor–acceptor systems: cycloaddition reactions of aryl-substituted olefins with tetracyanoethylene

Abstract

Cycloaddition reactions of several aryl-substituted olefins with tetracyanoethylene (TCNE) are reported. Ace-naphthylene, indene, 1-vinylpyrene, and vinylferrocene underwent [_π2 +_π2] Cycloaddition to give the corresponding cyclobutane derivatives, whereas 1-vinylnaphthalene and 9-vinylanthracene underwent Diels–Alder reactions. With 9-vinylanthracene the addition of TCNE occurred at the 9- and 10-positions, the vinyl group remaining unaffected. The reactions occurred under mild conditions, especially for 1-vinylnaphthalene, 1-vinylpyrene, 9-vinylanthracene, and vinylferrocene. They involved the formation of a charge transfer complex, the electronic spectrum of which was measured to estimate the ionization potential of the olefin. In general, the reactivity of the aryl-substituted olefin increased with decrease in its ionization potential. The 9-vinylanthracene–TCNE adduct dissociated readily in solution.