Iridium-Catalyzed Intramolecular C(sp ³ )–H/O–H Coupling: A Route to Benzofuran Derivatives Directly from 2-Alkylphenols through Dehydrogenative C–O Bond Formation between Alkyl and Hydroxy Groups

Ethers have typically been synthesized from alcohols using alkyl halides or alkenes. The C(sp3)–H/O–H coupling enables ethers to be synthesized directly from alcohols and alkanes, eliminating the need to prepare alkyl halides and alkenes. Herein, we describe an intramolecular C(sp3)–H/O–H coupling of 2-alkylphenols. We found that an iridium catalyst bearing DTBM-SEGPHOS, a bidentate phosphorus ligand, promotes the dehydrogenative formation of a C–O bond between the alkyl and hydroxy groups in 2-alkylphenols, affording benzofuran derivatives. The reaction proceeded efficiently when t-BuCH═CH2 (TBE) was used as the hydrogen scavenger. We also found that the iridium catalyst promotes the dehydrogenative transformation under oxidant-free conditions, affording the product with hydrogen evolution.