Copper-catalyzed Tandem Cyclization Reaction of Ethynylbenzoxazinones and Thiols: Facile Construction of 2-Thiomethylene Indoles

The first successful copper-catalyzed decarboxylative cyclization reaction of ethynylbenzoxazinones and thiols has been developed. A rarely studied α-addition process to a copper-allenylidene intermediate promoted this reaction. Using this protocol, a range of 2-thiomethylene indole compounds have been obtained. This methodology offers significant advantages including mild reaction conditions, cheap catalysts, good yields and broad substrate compatibility.