Benzocyclobutene radical anion

The radical anion of benzocyclobutene was prepared by metal and electrolytic reduction. Conclusive evidence is presented showing the fused, four-membered ring remains intact after reduction. An interesting temperature dependence was noted for the epr spectra of the metal-reduced benzocyclobutene. At low temperatures, the four methylene protons are nonequivalent but become equivalent as the temperature is raised. This phenomenon is discussed in terms of an ion pairing process. Finally, the effect of ring strain on spin densities and reduction potentials is discussed.