A palladium-catalyzed cyclization-carbonylation-coupling reaction between aryl halides and γ-Hydroxyallenes to form aryl (tetrahydrofuran-2-yl)vinyl ketones

Abstract

γ-Hydroxyallenes undergo cyclization-carbonylation-coupling with aryl (and one alkenyl) halides in the presence of catalytic Pd(PPh 3) 4, base, and CO to form the title ketones in good yields. The reaction was temperature dependent: at 80 °C, the CO insertion did not readily occur, while at 55–60 °C the ketone products predominated. Yields for the Pd(0)-catalyzed cyclization-coupling reaction (without insertion) improved when tert -butyl isocyanide was added (with no CO present), implying that a good π acid ligand improves the cyclization-coupling reactions between arylpalladium(II) halides and γ-hydroxyallenes.