Comparison of oxidative and excited state cyclizations of N-benzyldiphenylamines to N-benzylcarbazoles

Article abstract of DOI:10.1021/ja00103a014

Pulse radiolysis of a family of N-benzyldiphenylamines in aerated cyclohexane results in oxidative cyclization products, i.e., the corresponding N-benzylcarbazoles, as does direct photolysis at 254 nm. Chemical oxidation and bulk electrolysis lead to benzidine formation as the major product, with the competing cyclization pathway becoming minor. Photoinduced electron transfer sensitization induces formation of a radical ion pair in which back electron transfer quenches net reaction. No significant amounts of products deriving from bond cleavage of an intermediate cation radical could be detected in any of the reactions. AM1 calculations show lower barriers for the initial cyclization through a triplet state than through an intermediate cation radical or dication.