Ruthenium-Catalyzed Propargylic Reduction of Propargylic Alcohols with Hantzsch Ester

Abstract

Ruthenium-catalyzed propargylic reduction of propargylic alcohols bearing a terminal alkyne moiety is accomplished by using Hantzsch ester as a nucleophilic hydride source. A variety of secondary and tertiary propargylic alcohols are reduced to the corresponding propargylic reduced products such as 1-alkynes in excellent yields. Some mechanistic studies indicate that ruthenium–allenylidene complexes may work as key reactive intermediates.

Retro-Vinylidene Rearrangements of P- and S-Substituted Ruthenium Vinylidene Complexes

“…On the other hand, the reverse reaction, namely, retro-vinylidene (vinylidene-to-alkyne) rearrangement, have also been shown to proceed in several organometallic vinylidene complexes. However, despite continuous advances in the development of vinylidene rearrangements using internal alkynes, most of previous reports on retro-vinylidene rearrangements and its use in catalysis employ vinylidene complexes derived from terminal alkynes . Only limited information is available on the retro-vinylidene rearrangements of carbon-disubstituted , as well as heteroatom (Si, S)-substituted ,, vinylidene species.…”

Reactions of Ruthenabenzene with Propynols Involving Hydrogen-Bonding-Induced [2 + 2] Cycloaddition

“…insertion reactions, cycloaddition reactions, cyclopropanations, ylide formation followed by rearrangement, 1,2-migrations, etc. − Due to their diverse and controllable reactivity, they can be used to initiate cascade sequences, leading to the generation of complex structural motifs of enduring interest. One of the most well-studied chemistries of metal-carbene complexes is metathesis reactions. − The synthetically very important transformations usually react through elementary [2 + 2] cycloaddition steps that involve metallacyclobutene intermediates (Scheme a). The stability of metallacyclobutene is sensitively dependent on the electronic and steric properties of the ligands on the metal center and substituents of alkynes and thus greatly influence the following transformation processes.…”

Acidic Ionic Liquids as Metal-Free and Recyclable Catalysts for Direct Reduction of Aromatic Allylic Alcohol in Dimethyl Carbonate via Hydrogen Transfer

“…Therefore, direct reduction of alcohols has drawn more and more attention, and most activated alcohols, such as benzyl alcohols, allylic alcohols, , or propargyl alcohols, , have been successfully deoxidized. Transition metal complexes such as Ir, Mn, Ru, and so on with specific ligands were used as the catalysts to achieve direct reduction of alcohols by employing hydrosilane, silane, or hydrazine as the reducing agent (Scheme a). − In addition, Lewis acids were also favorable for the reaction by enhancing C–O bond cleavage and prolonging the existence of benzyl cation intermediates (Scheme b), thus creating an opportunity for effective hydrogen transfer . However, the transition metal complexes or Lewis acids were the main catalysts to achieve the C–O bond dissociation and further reduction of alcohols, easily leading to metal contamination. − …”