Cation radicals: ring opening of a cyclobutane by electron transfer

Abstract

One-electron oxidation of trans-1,2-di(carbazol-9-yl)cyclobutane (III) by tris-(p-bromophenyl)amine cation or by cerium(IV) in methanol solutions gives very high yields of the open chain methanolysis product 1,4-di(carbazol-9-yl)-1,4-dimethoxybutane (VI). The latter is also formed by oxidative coupling of N-vinylcarbazole in methanol and these observations demonstrate the ready interconvertibility of open-chain butane and cyclobutane cation radicals having carbazolyl substituents.