- Selective hydrogenation of lignin-derived compounds under mild conditions
-
A key challenge in the production of lignin-derived chemicals is to reduce the energy intensive processes used in their production. Here, we show that well-defined Rh nanoparticles dispersed in sub-micrometer size carbon hollow spheres, are able to hydrogenate lignin derived products under mild conditions (30 °C, 5 bar H2), in water. The optimum catalyst exhibits excellent selectivity and activity in the conversion of phenol to cyclohexanol and other related substrates including aryl ethers.
- Chen, Lu,Van Muyden, Antoine P.,Cui, Xinjiang,Laurenczy, Gabor,Dyson, Paul J.
-
supporting information
p. 3069 - 3073
(2020/06/17)
-
- Iron-Catalyzed Hydroamination and Hydroetherification of Unactivated Alkenes
-
The hydrofunctionalization of alkenes, explored for over 100 years, offers the potential for a direct, atom-economical approach to value-added products. While thermodynamically favored, the kinetic barrier to such processes necessitates the use of catalysts to control selectivity and reactivity. Modern variants typically rely on noble metals that require different ligands for each class of hydrofunctionalization, thereby limiting generality. This Letter describes a general iron-based system that catalyzes the hydroamination and hydroetherification of simple unactivated olefins.
- Marcyk, Paul T.,Cook, Silas P.
-
supporting information
p. 1547 - 1550
(2019/03/08)
-
- Palladium-Catalyzed Reductive Insertion of Alcohols into Aryl Ether Bonds
-
Palladium on carbon catalyzes C?O bond cleavage of aryl ethers (diphenyl ether and cyclohexyl phenyl ether) by alcohols (R?OH) in H2. The aromatic C?O bond is cleaved by reductive solvolysis, which is initiated by Pd-catalyzed partial hydrogenation of one phenyl ring to form an enol ether. The enol ether reacts rapidly with alcohols to form a ketal, which generates 1-cyclohexenyl?O?R by eliminating phenol or an alkanol. Subsequent hydrogenation leads to cyclohexyl?O?R.
- Wang, Meng,Gutiérrez, Oliver Y.,Camaioni, Donald M.,Lercher, Johannes A.
-
supporting information
p. 3747 - 3751
(2018/03/21)
-
- Ether Synthesis through Reductive Cross-Coupling of Ketones with Alcohols Using Me 2 SiHCl as both Reductant and Lewis Acid
-
We report that a Lewis acidic silane, Me 2 SiHCl, can mediate the direct cross-coupling of a wide range of carbonyl compounds with alcohols to form dialkyl ethers. The reaction is operationally simple, tolerates a range of polar functional groups, can be utilized to make sterically hindered ethers, and is extendable to sulfur and nitrogen nucleophiles.
- Lee, Yong Ho,Morandi, Bill
-
supporting information
p. 2425 - 2428
(2017/10/06)
-
- An efficient method for the reductive conversion of acyclic esters to ethers via a TMS-protected acetal
-
We report an efficient two step process for the reduction of non-aromatic esters to the corresponding ethers via the intermediate TMS-protected acetal. The acetal formed after the first step can be carried on directly to the subsequent reduction to the ether without purification. The ester reduction step was monitored using in-situ ReactIR for disappearance of the C[dbnd]O peak, allowing for the exact determination of time and equivalents of the reducing agent. Furthermore, use of TMS-imidazole to form the acetal has allowed us to dramatically reduce the overall reaction time required for the two step procedure.
- Hart, Alison,Kelley, Sarah A.,Harless, Tyler,Hood, John A.,Tagert, Michael,Pigza, Julie A.
-
p. 3024 - 3027
(2017/07/17)
-
- Palladium-Catalyzed Hydrolytic Cleavage of Aromatic C?O Bonds
-
Metallic palladium surfaces are highly selective in promoting the reductive hydrolysis of aromatic ethers in aqueous phase at relatively mild temperatures and pressures of H2. At quantitative conversions, the selectivity to hydrolysis products of PhOR ethers was observed to range from 50 % (R=Ph) to greater than 90 % (R=n-C4H9, cyclohexyl, and PhCH2CH2). By analysis of the evolution of products with and without incorporation of H218O, the pathway was concluded to be initiated by palladium metal catalyzed partial hydrogenation of the phenyl group to an enol ether. Water then rapidly adds to the enol ether to form a hemiacetal, which then undergoes elimination to cyclohexanone and phenol/alkanol products. A remarkable feature of the reaction is that the stronger Ph?O bond is cleaved rather than the weaker aliphatic O?R bond.
- Wang, Meng,Shi, Hui,Camaioni, Donald M.,Lercher, Johannes A.
-
supporting information
p. 2110 - 2114
(2017/02/15)
-
- Reductive fractionation of woody biomass into lignin monomers and cellulose by tandem metal triflate and Pd/C catalysis
-
A catalytic process for the upgrading of woody biomass into mono-aromatics, hemi-cellulose sugars and a solid cellulose-rich carbohydrate residue is presented. Lignin fragments are extracted from the lignocellulosic matrix by cleavage of ester and ether linkages between lignin and carbohydrates by the catalytic action of homogeneous Lewis acid metal triflates in methanol. The released lignin fragments are converted into lignin monomers by the combined catalytic action of Pd/C and metal triflates in hydrogen. The mechanism of ether bond cleavage is investigated by lignin dimer models (benzyl phenyl ether, guaiacylglycerol-β-guaiacyl ether, 2-phenylethyl phenyl ether and 2-phenoxy-1-phenylethanol). Metal triflates are involved in cleaving not only ester and ether linkages between lignin and the carbohydrates but also β-O-4 ether linkages within the aromatic lignin structure. Metal triflates are more active for β-O-4 ether bond cleavage than Pd/C. On the other hand, Pd/C is required for cleaving α-O-4, 4-O-5 and β-β linkages. Insight into the synergy between Pd/C and metal triflates allowed optimizing the reductive fractionation process. Under optimized conditions, 55 wt% mono-aromatics-mainly alkylmethoxyphenols-can be obtained from the lignin fraction (23.8 wt%) of birch wood in a reaction system comprising birch wood, methanol and small amounts of Pd/C and Al(III)-triflate as catalysts. The promise of scale-up of this process is demonstrated.
- Huang, Xiaoming,Morales Gonzalez, Olivia M.,Zhu, Jiadong,Korányi, Tamás I.,Boot, Michael D.,Hensen, Emiel J. M.
-
p. 175 - 187
(2017/01/24)
-
- A series of NiM (M = Ru, Rh, and Pd) bimetallic catalysts for effective lignin hydrogenolysis in water
-
In this paper, NiRu, NiRh, and NiPd catalysts were synthesized and evaluated in the hydrogenolysis of lignin C-O bonds, which is proved to be superior over single-component catalysts. The optimized NiRu catalyst contains 85% Ni and 15% Ru, composed of Ni surface-enriched, Ru-Ni atomically mixed, ultrasmall nanoparticles. The Ni85Ru15 catalyst showed high activity under low temperature (100°C), low H2 pressure (1 bar) in β-O-4 type C-O bond hydrogenolysis. It also exhibited significantly higher activity over Ni and Ru catalysts in the direct conversion of lignin into monomeric aromatic chemicals. Mechanistic investigation indicates that the synergistic effect of NiRu can be attributed to three factors: (1) increased fraction of surface atoms (compared with Ni), (2) enhanced H2 and substrate activation (compared with Ni), and (3) inhibited benzene ring hydrogenation (compared with Ru). Similarly, NiRh and NiPd catalysts were more active and selective than their single-component counterparts in the hydrogenolysis of lignin model compounds and real lignin.
- Zhang, Jiaguang,Teo, Jason,Chen, Xi,Asakura, Hiroyuki,Tanaka, Tsunehiro,Teramura, Kentaro,Yan, Ning
-
p. 1574 - 1583
(2014/05/20)
-
- CATALYTIC C-H BOND ACTIVATION FOR THE SYNTHESIS OF ETHERS AND THIOETHERS
-
Disclosed is a method for the transition metal-mediated oxidation of C-H bonds to form C-0 or C-S bonds. The methods are useful for the formation of ethers (R-OR') from alcohols, R'OH, and sp3 -hybridized C-H bonds in substrates, R-H. Aryl or heteroaryl acetates may also be used for C-H to C-OAr bond formation. The methods are also useful in the preparation of C-S bonds from acetyl-protected thiols, MeC(0)SR, and disulfides, RSSR. Advantageously, the methods minimize reaction steps, the handling of oxidized intermediates, and environmental impact.
- -
-
Page/Page column 5-6
(2014/01/08)
-
- Ruthenium complex-catalyzed novel transformation of alkyl formates
-
The following ruthenium-catalyzed novel transformations of alkyl formates have been developed: (1) selective decarbonylation of alkyl formates to the corresponding alcohols; (2) alkylation of arenes and alkenes using alkyl formates as an alkylating reagent via decarboxylation.Also the ruthenium-catalyzed addition of alcohols to alkenes has been developed as an appendant reaction, providing an effective method for the protection of alcohols.Keywords: Ruthenium; Catalysis; Alkyl; Arene; Alkene; Alcohol
- Kondo, Teruyuki,Kajiya, Satoshi,Tantayanon, Supawan,Watanabe, Yoshihisa
-
-