Novel applications of hypervalent iodine:: PIFA mediated synthesis of benzo[c]phenanthiridines and benzo[c]phenanthridinones

A short and efficient access to benzo[c]phenanthridines and phenanthridinones is achieved by the action of phenyliodine(m)-bis(trifluoroacetate) (PIFA) on properly substituted benzylnaphthylamines and naphthylbenzamides, respectively. This reagent promotes a non-phenolic oxidative biaryl coupling process, the key step of the synthesis. A study of the electronic and steric requirements of the substrates is carried out since, in some cases, dimerization processes prevail over intramolecular cyclization. A mechanistic proposal is also included. (C) 2001 Elsevier Science Ltd. All rights reserved.