1,4-Additions of tricyclic 1,4-diphosphinines - a novel system to study σ-bond activation and π-π dispersion interactions.

The dienic nature of the aromatic π-system in 1,4-diphosphinines remains largely unexplored to this day due to a lack of facile and efficient synthetic protocols. Recently reported stable, tricyclic 1,4-diphosphinines were used to explore the thermal reactivity of the π-system towards an array of dienophiles in [4π+2π]- and, for the first time, in [4π+2σ]-type cycloaddition reactions.