Gold(I)-Catalyzed Propargyl Claisen Rearrangement

The [3,3]-sigmatropic rearrangement of allyl vinyl ethers1 is an indispensable tool in organic synthesis, and catalysis of this reaction has further strengthened its impact.2 In general, Lewis acid catalysis of the Claisen rearrangement can be divided into two classes: hard Lewis acids, which catalyze the reaction by coordination to the oxygen atom,3 and soft Lewis acids, in particular those based on Hg(II) and Pd(II), which catalyze the reaction through coordination to the ð-bonds.4 The latter mode of catalysis is often limited by binding of the electrophilic metal to the strongly nucleophilic vinyl ether, thus preventing activation of the allylic olefin. Recent reports of Au(I)-catalyzed additions to alkynes,5 suggest that this limitation might be absent in a Au(I)-catalyzed acetylenic Claisen rearrange-ment.6 Importantly, a general catalytic version of the Claisen rearrangement of propargyl vinyl ethers has yet to be developed.7 In light of our previous success employing Ph3PAuOTf fo