Advances in the synthesis of polycyclic aromatic compounds

Renewed interest in the chemistry of polycyclic aromatic hydrocarbons (PAHs) has been stimulated by recent research advances in several areas. Prominent among these are: the discovery of buckminsterfullerene and related molecules; elucidation of the mechanisms of carcinogenesis of PAHs some of which are widespread contaminants in the human environment; and syntheses of large PAH ring systems that have interesting structural and electronic properties. These advances have fostered development of milder, more efficient methods for the synthesis of PAHs to replace older established methods that require drastic conditions and often afford relatively poor yields. This review provides an overview of methods for the synthesis of PAHs with emphasis on newer synthetic approaches. The latter include thermolysis and flash vacuum pyrolysis, inter- and intramolecular metal-catalyzed cross coupling reactions, such as Suzuki coupling, alkylation of activated forms of carbonyl compounds, such as enamines and silyl enol ethers, and cyclotrimerization of arynes and acetylenes. Recent advances and improvements in some of the established methods, such as oxidative photocyclization, Diels-Alder cycloaddition, and the Wittig reaction, are also covered.