Photochemical Approach to the Cyclohepta[<i>b</i>]indole Scaffold by Annulative Two‐Carbon Ring‐Expansion
Dina Christina Tymann, Lars Benedix, Lyuba Iovkova, Roman Pallach, Sebastian Henke, David Tymann, Martin Hiersemann
Abstract
We report on the implementation of the concept of a photochemically elicited two-carbon homologation of a π-donor-π-acceptor substituted chromophore by triple-bond insertion. Implementing a phenyl connector between the slide-in module and the chromophore enabled the synthesis of cylohepta[b]indole-type building blocks by a metal-free annulative one-pot two-carbon ring expansion of the five-membered chromophore. Post-irradiative structural elaboration provided founding members of the indolo[2,3-d]tropone family of compounds. Control experiments in combination with computational chemistry on this multibond reorganization process founded the basis for a mechanistic hypothesis.