A concise route to iboga-analogues via the formation of suitably substituted-2-indoles

A concise route to iboga-analogues has been developed. Important steps include a Pd-catalyzed Sonogashira coupling of Boc-2-idodaniline with terminal alkynes and the formation of 2-substituted indoles in the presence of tetrabutylammonium fluoride to give the key intermediate, dehydroisoquinuclidine-containing indole. The final step cyclization between indole-3-position and dehydroisoquinuclidine ring was achieved using Pd(II)-Ag(I) mixed metal-mediated cyclization method. Both exo- and endo-substitution with -CO2Me at C19 have been reported. (C) 2010 Elsevier Ltd. All rights reserved.