Efficient functionalization of aromatic C-H bonds catalyzed by gold(III) under mild and solvent-free conditions.

A gold(III)-catalyzed carbon-carbon bond formation reaction between arenes and electron-deficient alkynes or alkenes is described. Electron-rich arenes can be efficiently functionalized with the alkyne or alkene substrates. This reaction can be run with neat reactants at ambient temperature. Under the "solventless" conditions, clean product was obtained from a reaction of equal molar amounts of arene and alkyne substrates. The mild conditions and potential tolerance to different functional groups make this method practical for arene functionalization and for constructing complicated molecules. Efficient preparation of various coumarins from aryl alkynoates was demonstrated. Preliminary mechanistic studies were performed to probe the pathway of this reaction.