Synthesis of Cycloalkanoindoles by an Unusual DAST‐Triggered Rearrangement Reaction

Abstract

AbstractA series of 1,1‐bis(indol‐3‐yl) and 1‐(indol‐2‐yl)‐1‐(indol‐3‐yl)‐ψ‐hydroxyalkanes, prepared from the corresponding indole derivatives and suitable hydroxyaldehydes via routine coupling reactions, were treated with DAST (diethylaminosulfur trifluoride) under mild conditions, to generate a small library of cycloalkanoindoles. Irrespective of the substitution pattern, i.e. whether they are symmetrical or unsymmetrical derivatives, the same mixture of products is produced, in which the tetrahydro‐1H‐carbazole and hexahydrocyclohepta[b]indole scaffolds are substituted by a indol‐3‐yl nucleus on one of the two α‐carbon atoms of the cycloalkane moieties. Thus, speculations on the reaction mechanism with the prediction of a common reaction intermediate are presented. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)