Stereoselective Gold(I) Domino Catalysis of Allylic Isomerization and Olefin Cyclopropanation: Mechanistic Studies

Gold­(I)
catalysis of olefin activation is still a rare feature
in the repertoire of that metal. Mechanistic studies on the gold­(I)-catalyzed
cyclopropanation of allyl-substituted sulfonium ylides, including
kinetic analysis as well as detailed computational studies, reveal
that the reaction proceeds through activation of the alkene moiety.
Furthermore, a novel competitive allylic isomerization pathway that
interconverts “linear” and “branched”
allylic isomers is uncovered. The subtle interplay of cyclopropanation
and olefin isomerization results in an intriguing domino process where
two independent catalytic transformations combine with near-perfect
regio- and stereoselectivities.