4013-34-7Relevant academic research and scientific papers
Regioselective N-Functionalization of Tautomerizable Heterocycles through Methyl Trifluoromethanesulfonate-Catalyzed Substitution of Alcohols and Alkyl Group Migrations
Biswas, Srijit,Biswas, Subrata,Duari, Surajit,Elsharif, Asma M.,Maity, Srabani,Mishra, Abhishek Kumar,Morgon, Nelson H.,Roy, Arnab,de Souza, Aguinaldo R.
, (2022/01/20)
A catalytic synthetic strategy has been developed combining two protocols, such as, direct nucleophilic substitution of alcohols followed by X- to N- alkyl group migration (X=O, S) to access N-functionalized benzoxazolones, benzothiazolethiones, indolinone, benzoimidazolethiones, and pyridinones derivatives. Methyl trifluoromethanesulfonate (MeOTf) was found to catalyze the reaction, which revealed the catalytic property of MeOTf. A mechanism was established through experiments as well as DFT calculations wherein the ?OH group of alcohols were converted to the corresponding ?OMe groups and in situ generated TfOH. The ?OMe groups produced underwent TfOH catalyzed ?X alkylation (X=O, S) of the heterocycles followed by ?X- to ?N-alkyl group migrations in a single step. (Figure presented.).
Palladium-Catalyzed Alkoxycarbonylation of sec-Benzylic Ethers
Beller, Matthias,Jackstell, Ralf,Maes, Bert U. W.,Schneider, Carolin
supporting information, (2020/02/25)
Herein, we report the palladium-catalyzed synthesis of 3-arylpropionate esters starting from secondary benzylic ethers. With this investigation it could be shown that ethers are suitable starting materials in addition to the established carbonylation reactions of olefins, alcohols, or aryl halides.
Multiple Mechanisms Mapped in Aryl Alkyl Ether Cleavage via Aqueous Electrocatalytic Hydrogenation over Skeletal Nickel
Hegg, Eric L.,Jackson, James E.,Klinger, Grace E.,Saffron, Christopher M.,Zhou, Yuting
supporting information, p. 4037 - 4050 (2020/03/10)
We present here detailed mechanistic studies of electrocatalytic hydrogenation (ECH) in aqueous solution over skeletal nickel cathodes to probe the various paths of reductive catalytic C-O bond cleavage among functionalized aryl ethers relevant to energy science. Heterogeneous catalytic hydrogenolysis of aryl ethers is important both in hydrodeoxygenation of fossil fuels and in upgrading of lignin from biomass. The presence or absence of simple functionalities such as carbonyl, hydroxyl, methyl, or methoxyl groups is known to cause dramatic shifts in reactivity and cleavage selectivity between sp3 C-O and sp2 C-O bonds. Specifically, reported hydrogenolysis studies with Ni and other catalysts have hinted at different cleavage mechanisms for the C-O ether bonds in α-keto and α-hydroxy β-O-4 type aryl ether linkages of lignin. Our new rate, selectivity, and isotopic labeling results from ECH reactions confirm that these aryl ethers undergo C-O cleavage via distinct paths. For the simple 2-phenoxy-1-phenylethane or its alcohol congener, 2-phenoxy-1-phenylethanol, the benzylic site is activated via Ni C-H insertion, followed by beta elimination of the phenoxide leaving group. But in the case of the ketone, 2-phenoxyacetophenone, the polarized carbonyl πsystem apparently binds directly with the electron rich Ni cathode surface without breaking the aromaticity of the neighboring phenyl ring, leading to rapid cleavage. Substituent steric and electronic perturbations across a broad range of β-O-4 type ethers create a hierarchy of cleavage rates that supports these mechanistic ideas while offering guidance to allow rational design of the catalytic method. On the basis of the new insights, the usage of cosolvent acetone is shown to enable control of product selectivity.
In Situ Generation of Br?nsted Acidity in the Pd-I Bifunctional Catalysts for Selective Reductive Etherification of Carbonyl Compounds under Mild Conditions
Wu, Dan,Hernández, Willinton Y.,Zhang, Songwei,Vovk, Evgeny I.,Zhou, Xiaohong,Yang, Yong,Khodakov, Andrei Y.,Ordomsky, Vitaly V.
, p. 2940 - 2948 (2019/04/13)
Selective synthesis of ethers from biomass-derived carbonyl compounds is an important academic and industrial challenge. The existing processes based on strong acid or metallic catalysts cannot provide high selectivity to ethers due to the occurrence of side reactions. Hereby we propose a Pd-I bifunctional heterogeneous catalyst for the selective reductive etherification of aldehydes with alcohols. Extensive catalyst characterizations uncovered the presence of iodine species on the surface of Pd nanoparticles. Heterolytic dissociation of hydrogen on the I-Pd surface sites leads to the "in situ" generation of a Br?nsted acid, which promotes the reaction toward the corresponding ethers with extremely high selectivity under very mild reaction conditions.
Auto-Tandem Catalysis with Frustrated Lewis Pairs for Reductive Etherification of Aldehydes and Ketones
Bakos, Mária,Gy?m?re, ádám,Domján, Attila,Soós, Tibor
supporting information, p. 5217 - 5221 (2017/04/27)
Herein we report that a single frustrated Lewis pair (FLP) catalyst can promote the reductive etherification of aldehydes and ketones. The reaction does not require an exogenous acid catalyst, but the combined action of FLP on H2, R-OH or H2O generates the required Br?nsted acid in a reversible, “turn on” manner. The method is not only a complementary metal-free reductive etherification, but also a niche procedure for ethers that would be either synthetically inconvenient or even intractable to access by alternative synthetic protocols.
Oxidation of Secondary Methyl Ethers to Ketones
Gilissen, Pieter J.,Blanco-Ania, Daniel,Rutjes, Floris P. J. T.
supporting information, p. 6671 - 6679 (2017/07/15)
We present a mild way of converting secondary methyl ethers into ketones using calcium hypochlorite in aqueous acetonitrile with acetic acid as activator. The reaction is compatible with various oxygen- and nitrogen-containing functional groups and afforded the corresponding ketones in up to 98% yield. The use of this methodology could expand the application of the methyl group as a useful protecting group.
Thermal hazard evaluation of cumene hydroperoxide-metal ion mixture using DSC, TAM III, and GC/MS
You, Mei-Li
, (2016/06/15)
Cumene hydroperoxide (CHP) is widely used in chemical processes, mainly as an initiator for the polymerization of acrylonitrile-butadiene-styrene. It is a typical organic peroxide and an explosive substance. It is susceptible to thermal decomposition and is readily affected by contamination; moreover, it has high thermal sensitivity. The reactor tank, transit storage vessel, and pipeline used for manufacturing and transporting this substance are made of metal. Metal containers used in chemical processes can be damaged through aging, wear, erosion, and corrosion; furthermore, the containers might release metal ions. In a metal pipeline, CHP may cause incompatibility reactions because of catalyzed exothermic reactions. This paper discusses and elucidates the potential thermal hazard of a mixture of CHP and an incompatible material's metal ions. Differential scanning calorimetry (DSC) and thermal activity monitor III (TAM III) were employed to preliminarily explore and narrate the thermal hazard at the constant temperature environment. The substance was diluted and analyzed by using a gas chromatography spectrometer (GC) and gas chromatography/mass spectrometer (GC/MS) to determine the effect of thermal cracking and metal ions of CHP. The thermokinetic parameter values obtained from the experiments are discussed; the results can be used for designing an inherently safer process. As a result, the paper finds that the most hazards are in the reaction of CHP with Fe2+. When the metal release is exothermic in advance, the system temperature increases, even leading to uncontrollable levels, and the process may slip out of control.
Cleavage of the lignin β-O-4 ether bond: Via a dehydroxylation-hydrogenation strategy over a NiMo sulfide catalyst
Zhang, Chaofeng,Lu, Jianmin,Zhang, Xiaochen,Macarthur, Katherine,Heggen, Marc,Li, Hongji,Wang, Feng
supporting information, p. 6545 - 6555 (2018/06/06)
The efficient cleavage of lignin β-O-4 ether bonds to produce aromatics is a challenging and attractive topic. Recently a growing number of studies have revealed that the initial oxidation of CαHOH to CαO can decrease the β-O-4 bond dissociation energy (BDE) from 274.0 kJ mol-1 to 227.8 kJ mol-1, and thus the β-O-4 bond is more readily cleaved in the subsequent transfer hydrogenation, or acidolysis. Here we show that the first reaction step, except in the above-mentioned pre-oxidation methods, can be a Cα-OH bond dehydroxylation to form a radical intermediate on the acid-redox site of a NiMo sulfide catalyst. The formation of a Cα radical greatly decreases the Cβ-OPh BDE from 274.0 kJ mol-1 to 66.9 kJ mol-1 thereby facilitating its cleavage to styrene, phenols and ethers with H2 and an alcohol solvent. This is supported by control experiments using several reaction intermediates as reactants, analysis of product generation and by radical trap with TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) as well as by density functional theory (DFT) calculations. The dehydroxylation-hydrogenation reaction is conducted under non-oxidative conditions, which are beneficial for stabilizing phenol products.
Cooperative Catalysis of Noncompatible Catalysts through Compartmentalization: Wacker Oxidation and Enzymatic Reduction in a One-Pot Process in Aqueous Media
Sato, Hirofumi,Hummel, Werner,Gr?ger, Harald
supporting information, p. 4488 - 4492 (2015/04/14)
A Wacker oxidation using CuCl/PdCl2 as a catalyst system was successfully combined with an enzymatic ketone reduction to convert styrene enantioselectively into 1-phenylethanol in a one-pot process, although the two reactions conducted in aqueous media are not compatible due to enzyme deactivation by Cu ions. The one-pot feasibility was achieved via compartmentalization of the reactions. Conducting the Wacker oxidation in the interior of a polydimethylsiloxane thimble enables diffusion of only the organic substrate and product into the exterior where the biotransformation takes place. Thus, the Cu ions detrimental to the enzyme are withheld from the reaction media of the biotransformation. In this one-pot process, which formally corresponds to an asymmetric hydration of alkenes, a range of 1-arylethanols were formed with high conversions and 98-99% ee. In addition, the catalyst system of the Wacker oxidation was recycled 15 times without significant decrease in conversion.
Carbon-supported iron-ionic liquid: An efficient and recyclable catalyst for benzylation of 1,3-dicarbonyl compounds with alcohols
Moriel,Garcia
supporting information, p. 4306 - 4311 (2014/10/16)
The effect of the addition of ILs with non-coordinating anions on the iron-catalyzed benzylation of 1,3-dicarbonyl compounds with alcohols under solvent free conditions has been evaluated. Among them, the presence of those containing the bistriflimide anion was found to be crucial for selectivity towards the benzylated product in a homogenous reaction. Therefore, the catalytic activity of Fe(OTf)3-N4111NTf2 combination supported on carbon materials with different textural and chemical surface properties has been studied. In the heterogeneous phase, reaction selectivity was also enhanced by the addition of the IL. However, substantial differences between the activities of different Fe-IL/carbon material catalytic systems were observed, indicating the influence of carbon support properties. With regards to selectivity, the best results were obtained using carbon supports with low microporosity. Moreover, the presence of oxygen functional groups on the carbon surface improved catalyst recycling. the Partner Organisations 2014.
