Ruthenium-Catalyzed E-Selective Alkyne Semihydrogenation with Alcohols as Hydrogen Donors

Abstract

Selective direct ruthenium-catalyzed semihydrogenation of diaryl alkynes to the corresponding E-alkenes has been achieved using alcohols as the hydrogen source. The method employs a simple ruthenium catalyst, does not require external ligands, and affords the desired products in > 99% NMR yield in most cases (up to 93% isolated yield). Best results were obtained using benzyl alcohol as the hydrogen donor, although biorenewable alcohols such as furfuryl alcohol could also be applied. In addition, tandem semihydrogenation–alkylation reactions were demonstrated, with potential applications in the synthesis of resveratrol derivatives.

Ruthenium‐Catalyzed E‐Selective Partial Hydrogenation of Alkynes under Transfer‐Hydrogenation Conditions using Paraformaldehyde as Hydrogen Source

“…To investigate the scope of our reaction, different kinds of aliphatic and aromatic alkynes were employed under the obtained optimized conditions ( Figure 2). While other Rucatalyzed systems reduced aliphatic or aryl-alkyl alkynes only in low yields (< 25 %) and unselectively, [68] semi transfer hydrogenation of dialkyl substituted alkynes as well as unsymmetrical aryl-alkyl substituted and sole aromatic ones was done successfully and with good to excellent E-selectivity using our catalytic system. The reaction times were also noticeably short.…”

Electrochemical Proton Reduction over Nickel Foam for Z‐Stereoselective Semihydrogenation/deuteration of Functionalized Alkynes

“…It gives selective access to Z-alkenes, which have applications in materials chemistry as well as in the pharmaceutical industry. [1][2][3][4][5] The semireduction of alkynes is one of the few available methods for the formation of Z-alkenes. This reaction mainly uses palladium [6,7] (e. g., Lindlar), [8] rhodium, [9][10][11] ruthenium, [12] or iridium [13][14][15] catalysts in gas cylinders/pressurized reaction vessels.…”

“…The stereoselective synthesis of alkenes is a highly relevant reaction in synthetic organic chemistry. It gives selective access to Z ‐alkenes, which have applications in materials chemistry as well as in the pharmaceutical industry [1–5] . The semireduction of alkynes is one of the few available methods for the formation of Z ‐alkenes.…”

Highly Functional Group Tolerant, (E)-Selective Transfer Semihydrogenation of Alkynes Catalysed by Iridium Complex Bearing Unsymmetrical Ferrocene-Based Phosphine Ligand

“…One of them is a lack of complete stereoselectivity control leading to a mixture of isomers and thus affecting the yield and purification process of products. [19][20][21][22] An illustration of this may be work by Sun et al regarding iridium-based catalytic system using ethanol as a hydrogen donor. 23 Another limitation is the over-reduction of the triple C-C bond resulting in the formation of undesired alkane.…”

“…Furthermore, the majority of published semihydrogenation methods suffer from insufficient chemoselectivity. In particular, easily reducible functional groups such as formyl 25 , keto 20,26 , nitro 19-20, 22, 25, 27, 28-29 , cyano 30 , or aryl halides 21,26 are not tolerated. In many cases, explicit infor-mation concerning the compatibility of the above functional groups was not provided, which may obscure the actual efficiency of a given catalytic system.…”