Rearrangement of alkynyl sulfoxides catalyzed by gold(I) complexes.

Recently, gold-carbenoid species have been proposed as intermediates in gold-catalyzed enyne rearrangements.1 Additionally, the reaction of gold complexes with propargyl esters has been developed as an alternative approach to metal carbenoids capable of effecting olefin cyclopropanation;2,3 however, to date, the reaction of electrophilic metals with alkynes has not been amenable to the generation of R-carbonyl carbenoids analogous to those traditionally formed in situ from transition-metal-catalyzed decomposition of R-diazocarbonyl compounds.4,5 We recently described a rearrangement of homopropargyl azides to pyrroles in which gold(I) promotes addition of a leaving-group-bearing nucleophile (Nu ) N) to an acetylene and subsequent loss of the leaving group (LG ) N2) (eq 1).6 On the basis of this reactivity principle, we envisioned that R-carbonyl metal carbenoids could be generated from alkynes via a gold(I)-catalyzed rearrangement in which sulfoxides serve the role of nucleophile (Nu ) O) and latent leaving group (LG ) R2S).