COMPARISON OF OXIDATIVE AND EXCITED-STATE CYCLIZATIONS OF N-BENZYLDIPHENYLAMINES TO N-BENZYLCARBAZOLES

Pulse radiolysis of a family of N-benzyldiphenylamines in aerated cycl ohexane results in oxidative cyclization products, i.e., the correspon ding N-benzylcarbazoles, as does direct photolysis at 254 nm. Chemical oxidation and bulk electrolysis lead to benzidine formation as the ma jor product, with the competing cyclization pathway becoming minor. Ph otoinduced electron transfer sensitization induces formation of a radi cal ion pair in which back electron transfer quenches net reaction. No significant amounts of products deriving from bond cleavage of an int ermediate cation radical could be detected in any of the reactions. AM 1 calculations show lower barriers for the initial cyclization through a triplet state than through an intermediate cation radical or dicati on.