Comparison of Oxidative and Excited State Cyclizations of N-Benzyldiphenylamines to N-Benzylcarbazoles
摘要:
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.
Abstract Direct preparation of tertiary amines in which two substituents are aromatic is described. In the presence of either the inorganic base sodium tert-butoxide or the sterically hindered organic base diisopropylethylamine, the alkylation of secondary diarylamines is achieved smoothly. In contrast to methods previously reported in the literature, this procedure is high-yielding and does not require
Comparison of Oxidative and Excited State Cyclizations of N-Benzyldiphenylamines to N-Benzylcarbazoles
作者:Marye Anne Fox、Maria T. Dulay、Kevin Krosley
DOI:10.1021/ja00103a014
日期:1994.11
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.