Accessing Indenoazulenes <i>via</i> a Gold‐Catalysed Cyclisation of Cycloheptatrienyl‐Substituted 1,5‐Diynes
Alexandra V. Mackenroth, Alexander Ahrens, Jonas F. Wunsch, Raphael J. F. Berger, Frank Röminger, Matthias Rudolph, A. Stephen K. Hashmi
Abstract
Abstract Herein we report that cycloheptatrienyl‐substituted 1,5‐diynes with aromatic backbones undergo a gold‐catalysed 5‐ endo ‐ dig cyclisation to give 11 H ‐indeno‐[2,1‐ a ]azulenes at room temperature. This methodology complements the established range of aromatic structures obtained from gold‐catalysed conversions of differently substituted 1,5‐diynes accessed via highly reactive cationic intermediates. We have demonstrated the scope of the reaction and have assessed the possibility of further functionalisation of the indenoazulene scaffold. Additionally, we have studied the optical and electrochemical properties as well as the frontier molecular orbitals of this structural motif by both spectroscopic and theoretical means.