Gold-Catalyzed Propargylic Substitution Followed by Cycloisomerization in Ionic Liquid: Environmentally Friendly Synthesis of Polysubstituted Furans from Propargylic Alcohols and 1,3-Dicarbonyl Compounds

Gold-catalyzed propargylic substitution of propargylic alcohols 1 with 1,3-dicarbonyl compounds 2 followed by cycloisomerization in ionic liquid enables the environmentally friendly synthesis of polysubstituted furans 3 in good-to-high yields. The reaction proceeds via the hydrated propargylic substitution product 3″aa. The gold catalyst can be recycled at least three times.

[3 + 2] Coupling of Quinone Monoacetals with Vinyl Ethers Effected by Tetrabutylammonium Triflate: Regiocontrolled Synthesis of 2-Oxygenated Dihydrobenzofurans

The synthesis of 2-oxygenated dihydrobenzofurans involving the [3 + 2] coupling of quinone monoacetals with vinyl ethers has been realized by tetrabutylammonium triflate catalysis. The reaction involves a new activation method of the acetal moiety in quinone monoacetals under acid-free conditions affording the highly oxygenated dihydrobenzofurans. This new activation mode was achieved by using the triflate anion catalyst for stabilization of the highly reactive cationic intermediate.