Versatile Palladium-catalyzed intramolecular cyclization to access new luminescent azaphosphaphenalene motifs

Using a straightforward sequence of diphosphonylation and a Pd-catalysed concerted-metalation-deprotonation (CMD), a synthetic strategy towards polyaromatic phosphorus containing heterocycles was developed. Herein, we report the synthesis and characterization of new azaphosphaphenalenes, using easily accessible palladium catalysts and starting materials. The key tetrahydroquinoline intermediates of the reaction were synthesised via a fast and effective procedure and could be isolated as such, or further reacted towards the target polyaromatic structures. The obtained products showed interesting luminescent properties and their emission, excitation and quantum yields were evaluated. Herein a swift and versatile palladium cyclization is presented using readily accessible catalysts and starting materials to produce new azaphosphaphenalene motifs. The luminescent properties of these products were evaluated and some of the key compounds had their structure unambiguously confirmed by X-ray analysis. The phosphorus atom offers interesting possibilities for post functionalization. image