Gold‐Catalyzed Annulation of 1,8‐Dialkynylnaphthalenes: Synthesis and Photoelectric Properties of Indenophenalene‐Based Derivatives

A simple gold‐catalyzed annulation of 1,8‐dialkynylnaphthalenes utilizing a cationic gold catalyst was developed. Such a peri‐position of two alkynyl substituents has not been studied in gold catalysis before. Dependent on the substrate, the reactions either follow a mechanism involving vinyl cation intermediates or involve a dual gold catalysis mechanism which in an initial 6‐endo‐dig‐cyclization generates gold(I) vinylidene intermediates that are able to insert into C−H bonds. Indenophenalene derivatives were obtained in moderate to high yields. In addition, the bidirectional gold‐catalyzed annulation of tetraynes provided even larger conjugated π‐systems. The optoelectronic properties of the products were also investigated.
The 6‐endo‐cyclization of the first diyne unit (blue) with two alkynes in peri‐position induces a switch to a 5‐exo‐cyclization for the second peri‐diyne unit (red) in the fast modular synthesis of new extended π‐systems.