Selective Borylation of C(sp3)−H Bond of Methyl Ethers Catalyzed by Iron Complexes Bearing Anionic Benzene-Based PCP-Pincer Ligands

Abstract

Highly selective catalytic C(sp³)−H borylation of methoxy groups has been achieved using newly synthesized iron complexes bearing benzene-based PCP-type pincer ligands as catalysts. Reactions of various aryl and alkyl methyl ethers as substrates with bis(pinacolato)diboron under mild reaction conditions proceeded to afford the corresponding methoxy borylated products in good to high yields. A successful example of the iron-catalyzed C(sp³)−H borylation of a methylene group of tetrahydrofuran (THF) was also presented. A plausible reaction pathway is proposed based on the experimental result of some stoichiometric reactions and DFT calculations on a model reaction, where iron-boryl and -alkyl complexes may work as key intermediates.