Palladium-catalyzed cyclization reactions of propargylic carbonates with nucleophiles: a methodology for the syntheses of substituted 2,3-dihydrofurans and benzofurans

Phenoxy-substituted 2,3-dihydrofurans were synthesized by the palladium-catalyzed reaction of 5-methoxycarbonyloxy-3-pentyn-1-ol with phenols. The propargylic carbonate containing a nucleophilic phenoxy group also reacted in the presence of palladium to produce the product. The reaction of 1-(2-hydroxyphenyl)-3-methoxycarbonyloxy-1-propyne with 2-methyl-1,3-cyclohexanedione or 2-methyl-1,3-cycohexanedione yielded the substituted benzofurans. The propargylic compound having a acetoxy group as a leaving group exhibited similar reactivity.