Ligand-Assisted Gold-Catalyzed Efficient Alkynylative Cyclization with Terminal Alkynes Using H2O2 as Oxidant

The gold-catalyzed cyclization-functionalization is a powerful approach to construct high-value organic molecules. However, current strategies mainly rely on expensive external oxidants or pre-functionalized substrates, which exhibit low atom economy and high costs. Considering the current increasing demand for environmentally friendly and atomically efficient processes, the development of greener and more efficient synthetic strategies becomes more valuable and attractive. To circumvent these drawbacks, we developed a green gold-catalyzed cyclization-functionalization strategy using hydrogen peroxide as oxidant. A direct construction of 3-alkynylbenzofurans from terminal alkynes was possible by this gold-catalyzed process. Green and inexpensive oxidants, simple gold catalysts, mild reaction conditions, high atom economy, remarkable selectivity, wide substrate scope, broad functional group compatibility and a facile gram-scale synthesis make this alkynylative cyclization method practical for many forms of cyclization reactions. In contrast to prior methods neither pre-functionalized alkynes nor expensive external oxidants are needed.