Activation of Mononuclear Arene Ruthenium Complexes for Catalytic Propargylation Directly with Propargyl Alcohols

Abstract Mononuclear complexes of the type [(p‐cymene)RuX(CO)(PR3)][OTf] (R=Ph, Cy; X=Cl, OTf) promote the direct catalytic propargylation of furan with propargyl alcohols. These precursors are generated in situ from [(p‐cymene)RuCl(OTf)(PR3)] by activation of the propargylic alcohol, leading to the carbonyl ligand formation via allenylidene and alkenyl‐hydroxycarbene intermediates. The generation of the catalytically active species requires a short initial thermal activation to induce decoordination of the p‐cymene ligand. The in situ generated catalyst has been applied to catalytic transformations of alkynes and propargylic alcohols: propargylation of furans, propargyl ether synthesis from internal and terminal propargylic alcohols with propargyl, homopropargyl and allyl alcohols, selective dimerization of phenylacetylene into E‐enyne, and propargyl alcohol rearrangement into α,β‐unsaturated aldehydes and ketones via the Meyer–Schuster rearrangement. The propargylation of propargylic alcohols containing internal CC bonds suggests an activation via the Nicholas‐type intermediate, the metal‐stabilized propargyl cation.