Chinese scientists report a new and economical route to polycyclic aromatic compounds. 

Jin-Heng Li and co-workers from Hunan Normal University and Wenzhou University have developed an iron-catalysed intramolecular annulation route to the synthesis of naphthalen-1-ol and anthracen-1-ol core structures. Li believes that this new atom-economical method will provide a potential route to designing the achiral/chiral hydroxy-containing ligands. Surprisingly, the iron catalyst is the commercially available iron trichloride (FeCl₃) which is cheap and affordable. Li explains that this reaction presents the first example of an intramolecular annulation reaction of an alkyne with a carbon nucleophile for the synthesis of substituted naphthalenol and anthracenol structures. 

Transition metal-catalysed annulation reactions have previously been reported but suffer from several disadvantages such as harsh conditions, inaccessible substrates and sometimes expensive catalysts. The route developed by Li and co-workers is more atom economical overall, and uses a cheap iron-catalyst and starting materials that are easily prepared. 

Li believes the mechanism of this reaction involves a Diels-Alder process, but points out that this will be the next challenge for chemists in this field; trapping the iron intermediates of the reaction in order to define the mechanism of the process. 

Mary Badcock