Cu(II)-mediated generation of triarylamine radical cations and their dimerization. an easy route to tetraarylbenzidines.
Triphenylamine (TPA) derivatives react with Cu2+ in acetonitrile to give TPA radical cations which undergo dimerization and deprotonation reactions to yield tetraphenylbenzidines (TPB). Synthetic utility of this reaction is demonstrated using several triphenylamine derivatives, and yields in excess of 80% are obtained in most cases. Involvement of the amine radical cations in these reactions was confirmed by ESR and absorption spectroscopic studies. A mechanism consistent with all observations is proposed. This study also revealed a very good correlation between the free energy change for radical cation formation and product yields.
Sreenath
Kesavapillai
K
Photosciences and Photonics, Chemical Sciences and Technology Division, National Institute for Interdisciplinary Science and Technology, Trivandrum 695 019, India.
Suneesh
Chettiyam Veettil
CV
Kumar
Venugopal K Ratheesh
VK
Gopidas
Karical R
KR