Acceptorless dehydrogenative coupling of alcohols catalysed by ruthenium PNP complexes: Influence of catalyst structure and of hydrogen mass transfer

Zhang, Lei; Raffa, Guillaume; Nguyên, Duc Hanh; Swesi, Youssef; Corbel-Demailly, Louis; Capet, Frédéric; Trivelli, Xavier; Desset, Simon; Paul, Sébastien; Paul, Jean‐François; Fongarland, Pascal; Dumeignil, Franck; Gauvin, Régis M.

doi:10.1016/j.jcat.2016.06.001

Cited by 50 publications

(46 citation statements)

References 69 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…When EtOH was used, ethyl acetate was detected in the reaction mixture as a major side product, which is formed upon reaction of EtOH with acetaldehyde to the hemiacetal, followed by its dehydrogenation (Scheme ). Previous reports on transfer hydrogenation reactions with EtOH also report ester formation . We assume that some acetaldehyde also reacts with 8 a and 9 a as this accounts for the unidentified side products found in this reaction.…”

Section: Resultssupporting

confidence: 54%

Selective Base‐free Transfer Hydrogenation of α,β‐Unsaturated Carbonyl Compounds using iPrOH or EtOH as Hydrogen Source

Farrar‐Tobar

Wei

Jiao

et al. 2018

Chemistry A European J

View full text Add to dashboard Cite

Commercially available Ru-MACHO -BH is an active catalyst for the hydrogenation of several functional groups and for the dehydrogenation of alcohols. Herein, we report on the new application of this catalyst to the base-free transfer hydrogenation of carbonyl compounds. Ru-MACHO -BH proved to be highly active and selective in this transformation, even with α,β-unsaturated carbonyl compounds as substrates. The corresponding aliphatic, aromatic and allylic alcohols were obtained in excellent yields with catalyst loadings as low as 0.1-0.5 mol % at mild temperatures after very short reaction times. This protocol tolerates iPrOH and EtOH as hydrogen sources. Additionally, scale up to multi-gram amounts was performed without any loss of activity or selectivity. An outer-sphere mechanism has been proposed and the computed kinetics and thermodynamics of crotonaldehyde and 1-phenyl-but-2-en-one are in perfect agreement with the experiment.

show abstract

Section: Resultssupporting

confidence: 54%

Selective Base‐free Transfer Hydrogenation of α,β‐Unsaturated Carbonyl Compounds using iPrOH or EtOH as Hydrogen Source

Farrar‐Tobar

Wei

Jiao

et al. 2018

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“… 7 This reaction and the reverse reaction (hydrogenation of esters to alcohols) 8 have garnered much interest both synthetically and mechanistically. 9 A logical progression from these now well-studied systems would be to use the same approach to develop the dehydrogenative synthesis of thioesters from alcohols and thiols, and the reverse hydrogenation of thioesters with H 2 . However, clear challenges exist in that (i) the chemoselectivity of such processes may compete with thermodynamically preferable ester formation, whether from the dehydrocoupling of alcohols 7 or the homocoupling of aldehydes; 10 (ii) thiols are typically significantly more acidic than alcohols, 11 as such, when utilized as substrates or generated as products, they are likely to poison classically utilized pincer catalysts; 12 and (iii) generally, thiols exhibit strong coordination to metal centers, 13 possibly inhibiting catalytic activity.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Investigations of Ruthenium Catalyzed Dehydrogenative Thioester Synthesis and Thioester Hydrogenation

et al. 2021

View full text Add to dashboard Cite

We have recently reported the previously unknown synthesis of thioesters by coupling thiols and alcohols (or aldehydes) with liberation of H 2 , as well as the reverse hydrogenation of thioesters, catalyzed by a well-defined ruthenium acridine-9H based pincer complex. These reactions are highly selective and are not deactivated by the strongly coordinating thiols. Herein, the mechanism of this reversible transformation is investigated in detail by a combined experimental and computational (DFT) approach. We elucidate the likely pathway of the reactions, and demonstrate experimentally how hydrogen gas pressure governs selectivity toward hydrogenation or dehydrogenation. With respect to the dehydrogenative process, we discuss a competing mechanism for ester formation, which despite being thermodynamically preferable, it is kinetically inhibited due to the relatively high acidity of thiol compared to alcohol and, accordingly, the substantial difference in the relative stabilities of a ruthenium thiolate intermediate as opposed to a ruthenium alkoxide intermediate. Accordingly, various additional reaction pathways were considered and are discussed herein, including the dehydrogenative coupling of alcohol to ester and the Tischenko reaction coupling aldehyde to ester. This study should inform future green, (de)hydrogenative catalysis with thiols and other transformations catalyzed by related ruthenium pincer complexes.

show abstract

“…Additionally, we considered whether the ability to promote HCOOH disproportionation beside dehydrogenation is characteristic for molybdenum or might be instead achieved with other metals supported by the aliphatic PNP ligand ( Scheme 3 ). Thus, pincer complexes of Ru, 10 , 30 Ir, 11 , 31 Mn, 12 32 as well as Fe, 13 33a,b and 14 , 33 were selected which would require no additive to generate an active catalytic species ( Scheme 3 ). However, under the applied reaction conditions, only the ruthenium catalyst 10 promoted HCOOH dehydrogenation ( Table 2 , entry 8, total evolved gas volume 347 mL) but in no case methanol or methyl formate were detected.…”

Section: Resultsmentioning

confidence: 99%

HCOOH disproportionation to MeOH promoted by molybdenum PNP complexes

et al. 2021

View full text Add to dashboard Cite

show abstract

Acceptorless dehydrogenative coupling of alcohols catalysed by ruthenium PNP complexes: Influence of catalyst structure and of hydrogen mass transfer

Cited by 50 publications

References 69 publications

Selective Base‐free Transfer Hydrogenation of α,β‐Unsaturated Carbonyl Compounds using iPrOH or EtOH as Hydrogen Source

Selective Base‐free Transfer Hydrogenation of α,β‐Unsaturated Carbonyl Compounds using iPrOH or EtOH as Hydrogen Source

Mechanistic Investigations of Ruthenium Catalyzed Dehydrogenative Thioester Synthesis and Thioester Hydrogenation

HCOOH disproportionation to MeOH promoted by molybdenum PNP complexes

Contact Info

Product

Resources

About