Cascade Cross-Coupling/[3,3]-Sulfonium Rearrangement of Alkynyl Sulfoxides and Ynamides/Ynol Ethers to Construct Tetrasubstituted Furans
A transition-metal-free strategy for the synthesis of tetrasubstituted furans is reported.Promoted by boron trifluo-ride diethyl etherate,the reaction of alkynyl sulfoxides with ynamides/ynol ethers proceeded via a cascade process including cross-coupling of the two reactants,[3,3]-sulfonium rearrangement,and 5-exo-dig heterocyclization,leading to tetrasubstituted furan products.The resultant α-alkylthio groups can be used for further functionalization,such as to introduce other alkyl/aryl groups.