Benzofurans are heterocycles composed of fused benzene and furan rings. They are ubiquitous in many biologically active natural and synthetic molecules, polymers, and pharmaceuticals. Examples of clinically approved drugs containing benzofuran include amiodarone (irregular heartbeat and tachycardia treatment), vilazodone (novel SSRI inhibitor), and naloxone (narcotic overdose treatment). Therefore, benzofurans are important molecular scaffolds in drug discovery and medicinal chemistry. There is a sustained interest in the development of new catalytic methods for the synthesis of benzofurans, which is the focus of this study. In our recent publication, we demonstrated that aryl alkyl sulfides readily cyclize onto activated aryl alkynes activated by a gold(I)-NHC complex. We discovered that a similar reactivity can be achieved for far less reactive aryl alkyl ethers when Nolan’s gold(I)-IPr hydroxide tetrafluroroborate dimer catalyst is used. The reaction proceeds smoothly at room temperature and uses very small amounts of the catalyst. Brønsted acid co-catalyst is no longer required because catalyst turnover is facilitated by the migration of the electron-rich alkyl group. Our method tolerates substrates with functional groups that have various steric and electronic properties. We will present the details of reaction optimization as well as discuss the possible reaction mechanism.
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