Some Developments in the High Temperature Gas Phase Chemistry of Alkynes, Arynes and Aryl Radicals

The discovery of the equilibration of alkynes with ylidenecarbenes at high temperatures has been followed by increasing use of the reactivity of such carbenes in the synthesis of polycyclic aromatic hydrocarbons. This has led to simple and elegant syntheses of fullerene fragments, and of cyclopenta-fused hydrocarbons. The related high-temperature equilibration of arynes with ring-contracted exocyclic carbenes has provided a further pathway for the transformation of polycyclic aromatic systems into less accessible cyclopenta-fused hydrocarbons. Some recent developments in the chemistry of aryl radicals have extended the scope of radical approaches to the synthesis of polycyclic hydrocarbons.