Iridium-catalyzed Vinylic C–H Borylation of Cyclic Vinyl Ethers by Bis(pinacolato)diboron

Abstract

Abstract Vinylic C–H borylation of cyclic vinyl ethers by bis(pinacolato)diboron was effectively catalyzed by iridium complexes comprised of 1/2[Ir(OMe)(cod)]2 and 4,4′-di-tert-butyl-2,2′-bipyridine in hexane or octane to give the corresponding vinylboron compounds in good yields. The reaction of 1,4-dioxene occurred even at room temperature, whereas the reactions of dihydropyran and dihydrofuran derivatives required a temperature above 80 °C. Although dihydropyran and dihydrofuran themselves produced regioisomeric mixtures of α- and β-borylated products, similar substrates possessing substituents at the γ-position selectively underwent borylation at the α-position.