A PALLADIUM-CATALYZED CYCLIZATION-CARBONYLATION-COUPLING REACTION BETWEEN ARYL HALIDES AND GAMMA-HYDROXYALLENES TO FORM ARYL (TETRAHYDROFURAN-2-YL)VINYL KETONES

gamma-Hydroxyallenes undergo cyclization-carbonylation-coupling with a ryl (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 reactio n was temperature dependent: at 80 degrees C, the CO insertion did not readily occur, while at 55-60 degrees C the ketone products predomina ted. Yields for the Pd(O)-catalyzed cyclization-coupling reaction (wit hout insertion) improved when tert-butyl isocyanide was added (with no CO present), implying that a good pi acid ligand improves the cycliza tion-coupling reactions between arylpalladium(II) halides and gamma-hy droxyallenes.