Formation of Cyclic Ethers via the Palladium-Catalyzed Cycloaddition of Activated Olefins with Allylic Carbonates Having a Hydroxy Group at the Terminus of the Carbon Chain
The reaction of 1 with the hydroxyallylic carbonate 3 in the presence of catalytic amounts of Pd(2)dba(3).CHCl(3) and (o-tolyl)(3)P in THF at 50 degrees C afforded the corresponding cycloaddition products, tetrahydropyran derivatives 6, in good to high yields. The trans/cis ratios of the products were in the range of ca. 0-40/99-80. The reaction of 1a with the hydroxyallylic carbonate 4 needed higher