Supramolecular-induced regiocontrol over the photochemical [4 + 4] cyclodimerization of NHC- or azole-substituted anthracenes.

Thanks to the impressive control that microenvironments within enzymes can have over substrates, many biological reactions occur with high regio- and stereoselectivity. However, comparable regio- and stereoselectivity is extremely difficult to achieve for many types of reactions, particularly photochemical cycloaddition reactions in homogeneous solutions. Here, we describe a supramolecular templating strategy that enables photochemical [4 + 4] cycloaddition of 2,6-difunctionalized anthracenes with unique regio- and stereoselectivity and reactivity using a concept known as the supramolecular approach. The reaction of 2,6-azolium substituted anthracenes H-(PF) ( = ) with AgO yielded complexes -[Ag ](PF) featuring an antiparallel orientation of the anthracene groups. Irradiation of complexes -[Ag ](PF) proceeded under [4 + 4] cycloaddition linking the two anthracene moieties to give cyclodimers -[Ag()](PF). Reaction of 2,6-azole substituted anthracenes with a dinuclear complex [Cl-Au-NHC-NHC-Au-Cl] yields tetranuclear assemblies with the anthracene moieties oriented in -fashion. Irradiation and demetallation gives a [4 + 4] -photodimer of two anthracenes. The stereoselectivity of the [4 + 4] cycloaddition between two anthracene moieties is determined by their orientation in the metallosupramolecular assemblies.