A phosphine-mediated reaction of cyclic 1,2-diones and 3-alkyl allenoates: an efficient protocol for benzannulation applicable to the synthesis of polycyclic aromatic hydrocarbons.

A facile one-pot benzannulation strategy involving phosphine-3-alkyl allenoate zwitterions and cyclic 1,2-diones is described. The strategy is effectively utilized in the synthesis of fluoranthenes and benzo[a]aceanthrylenes with impressive photophysical properties. This is the first report on an intermolecular benzannulation using a 3-alkyl allenoate as a four carbon synthon.