The diphenylmethylenecyclohexane, 2, and the substituted 2-methyleneadamantanes, 3-7, have been prepared. The radical cation of each was generated by photochemical oxidation using 1, 4-dicyanobenzene as the sensitizer, and their reactivity was examined in methanol- acetonitrile mixtures with added tetraethylammonium cyanide. Although compound 2 reacted only by tautomerization, the other compounds all gave addition products. For the ...