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

Abstract

Abstract Mononuclear complexes of the type [( p‐ cymene)RuX(CO)(PR 3 )][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)(PR 3 )] 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.