Target cum Flexibility: Synthesis of Indolo[1,2-b]isoquinoline Derivatives via Cobalt-Catalyzed [2+2+2] Cyclotrimerization

Abstract

A modular approach for the synthesis of small molecules having the unnatural 6,11-dihydroindolo[1,2-<i>b</i>]isoquinoline tetracyclic core has been documented. An acid-catalyzed Friedel–Crafts-type C2-alkylation of <i>N</i>-propargyl indole with a suitably activated alkynol has been used to prepare the key indole-derived diynes. The cobalt-catalyzed [2+2+2] cyclotrimerization of these diynes has been studied with various internal/terminal alkynes and with nitriles.