Cyclizations of unsymmetrical bis-1,2-(3-indolyl)ethanes: Synthesis of (−)-tjipanazole F1

The inter- and intramolecular dimerization of 3-substituted indoles was studied. The rate and extent of dimerization depends on the indole substituents The intramolecular dimerization of unsymmetrical bis-1,2-(3-indolyl)ethanes could be controlled using either thermodynamic reaction conditions (neat trifluoroacetic acid) or kinetic conditions (2 equiv acid/chloroform). This control of regiochemistry has been applied to an efficient synthesis of (-)-jipanazole F1. (C) 1997 Elsevier Science Ltd.