Pentannulation Reaction by Tandem Gold(I)-Catalyzed Propargyl Claisen Rearrangement/Nazarov Cyclization of Enynyl Vinyl Ethers

The tandem gold(I)-catalyzed propargyl Claisen rearrangement/Nazarov cyclization of propargyl vinyl ether derivatives, followed by in situ reduction of the resulting carbonyl group, provides functionalized cyclopentadienes fused with various N-hetero- and carbacycles, including indoles, in good to excellent yields. The reaction occurs with high regioselectivity, with the position of the double bonds in the five-membered ring depending on the type of (hetero)cycle bearing the propargylic moiety and the side chain on the latter.