Extrapolation of the gold-catalyzed cycloisomerization to the palladium-catalyzed cross-coupling/cycloisomerization of acetylenic alcohols for the synthesis of polysubstituted furans: Scope and application to tandem processes

This paper describes the development of an integrated approach for the preparation of diverse furan derivatives from acetylenic alcohols by gold and palladium catalyzed π-activation chemistry. Notably, this new method was found to be amenable to cyclooctyl-containing substrates, which represents a significant extension to this methodology compared with our previous reports. Furthermore, this newly developed method allowed for the direct construction of cyclooctyl furans from their synthetic precursors under Sonogashira conditions. Experimental results revealed that palladium played two major functions in these reactions, including (1) an essential catalyst in the cross-coupling reaction of the substrates; and (2) facilitating the cyclization of the acetylenic alcohol intermediates through a typical π-activation process. The scope of this chemistry was highlighted by the one-pot synthesis of 3-iodofuran, which provided an opportunity for further functionalization (via coupling methods). Finally, the AuBr3 protocol was also elaborated to domino cyclization/C–H activation reactions, as well as the cyclization of acyclic precursors. Taken together, the results of this study demonstrate that gold and palladium catalysts can be used to complement each other in cyclization reactions.

Graphical AbstractFuran derivatives have been efficiently synthesized from acetylenic alcohols using a combination of gold and palladium catalysis. The utility of this protocol has been highlighted by performing several tandem and one-pot reactions.Figure optionsDownload as PowerPoint slide