Benzyl Carbonates Research Articles

Effect of Ce2O3 phase transition on the catalytic oxidation for toluene over CeO2 catalysts

Cerium oxide was a potential replacement for precious metals as a catalyst for VOCs. Here, we prepared CeOx-350, CeOx-450, CeOx-550 and CeOx-650 catalysts by controlling the calcination temperature, the occurrence of Ce2O3 localized phase transitions at CeOx-350 and CeOx-550 was confirmed by XRD, HRTEM and TGA. This localized phase transition caused the change in specific surface area and crystallinity, and prolonged the Ce-O-Ce bond lengths at the heterogeneous interfaces, enhancing the redox capacity and activity of oxygen species. CeOx-550 exhibited the optimal low-temperature activity towards toluene due to the highest Ce3+ content, oxygen vacancy content and the best activity of reactive oxygen species. The oxidation of toluene experienced intermediates of benzyl alcohol, benzaldehyde, benzoate, maleic acid and carbonates. Among them, benzoic acid was the decisive step in the toluene oxidation pathway. Combined with the reaction pathway of toluene, the reaction stages of different oxygen species were determined. The active oxygen species located at the heterogeneous interface would serve as an adsorption site for toluene. The Ce2O3 phase would participate in the deep oxidation of toluene as an active site, which was equivalent to the oxygen vacancies. This study was conducted to explore the effect of local phase transition on catalytic activity, which provided a new strategy for the synthesis of highly active cerium oxide catalysts.

Low Pressure Carbonylation of Benzyl Carbonates and Carbamates for Applications in13C Isotope Labeling and Catalytic CO2Reduction

AbstractHerein, we report a methodology to access isotopically labeled esters and amides from carbonates and carbamates employing an oxygen deletion strategy. This methodology utilizes a decarboxylative carbonylation approach for isotope labeling with near stoichiometric, ex situ generated12C, or13C carbon monoxide. This reaction is characterized by its broad scope, functional group tolerance, and high yields, which is showcased with the synthesis of structurally complex molecules. A complementary method that operates by the catalytic in situ generation of CO via the reduction of CO2liberated during decarboxylation has also been developed as a proof‐of‐concept approach that CO2‐derived compounds can be converted to CO‐containing frameworks. Mechanistic studies provide insight into the catalytic steps which highlight the impact of ligand choice to overcome challenges associated with low‐pressure carbonylation methodologies, along with rational for the development of future methodologies.

Low Pressure Carbonylation of Benzyl Carbonates and Carbamates for Applications in 13 C Isotope Labeling and Catalytic CO2 Reduction.

Herein, we report a methodology to access isotopically labeled esters and amides from carbonates and carbamates employing an oxygen deletion strategy. This methodology utilizes a decarboxylative carbonylation approach for isotope labeling with near stoichiometric, ex situ generated 12 C, or 13 C carbon monoxide. This reaction is characterized by its broad scope, functional group tolerance, and high yields, which is showcased with the synthesis of structurally complex molecules. A complementary method that operates by the catalytic in situ generation of CO via the reduction of CO2 liberated during decarboxylation has also been developed as a proof-of-concept approach that CO2 -derived compounds can be converted to CO-containing frameworks. Mechanistic studies provide insight into the catalytic steps which highlight the impact of ligand choice to overcome challenges associated with low-pressure carbonylation methodologies, along with rational for the development of future methodologies.

Carbon Dioxide Mediated Cellulose Dissolution and Derivatization to Cellulose Carbonates in a Low-pressure System

An effective switchable solvent system using carbon dioxide (CO2) and 2-tert-butyl-1,1,3,3-tetramethylguanidine (BTMG) for cellulose dissolution and derivatization was developed. High concentration cellulose solution (up to 10 wt%) could be achieved by dissolving microcrystalline cellulose rapidly, within 5 min, into DMSO in presence of BTMG and 1 atm CO2 at room temperature. The cellulose-carbonate anion intermediate was characterized by 1H and 13C NMR spectroscopies, emphasizing the generation of cellulose carbonate anions and protonated BTMG. Addition of organochlorides into the cellulose solution triggers a nucleophilic substitution with cellulose-carbonate anions, producing various cellulose benzyl carbonates and a cellulose-carbonate-ester with degree of substitution (DS) up to 1.83 at 1 atm CO2 pressure and room temperature. The activation energy (Ea) and Gibbs free energy change (ΔG) of CO2-mediated dissolution and nucleophilic substitution were calculated by density functional theory. The results showed that the nucleophilic substitution is the rate-limiting step.

Palladium-catalyzed sulfonylative coupling of benzyl(allyl) carbonates with arylsulfonyl hydrazides

An efficient palladium-catalyzed sulfonylative coupling for the synthesis of benzyl(allyl) sulfones from sulfonyl hydrazides and carbonates was developed. The novel methodology employs easily accessible chemical feedstocks including stable and readily available arylsulfonyl hydrazides and benzyl(allyl) carbonates. A variety of benzyl(allyl) sulfones could be obtained in good to excellent yields in the presence of Pd(dppf)Cl2 without additional base under mild conditions.

Electrochemical Fixation of Carbon Dioxide: Synthesis of Carboxylic Acids.

In the past three decades, we have focused on the fixation of carbon dioxide by electrochemical method with a carbon-carbon bond forming reaction to yield carboxylic acid, so-called electrochemical carboxylation. Vinyl bromides and triflates, difluoroethylbenzenes, polyfluoroarenes, benzal diacetates, phenyl-substituted alkenes and enamides, and α-aminosulfones were found to be effective as substrates for electrochemical carboxylation. Phenylacetic acids and phenylpropanoic acids including non-steroidal anti-inflammatory agents and their fluorinated analogues, polyfluorobenzoic acids, mandel acetates, and α- and β-amino acids were successfully synthesized. Electrochemical double carboxylation of dibenzyl carbonates, reuse of carbon dioxide in benzyl carbonates for fixation of carbon dioxide (recycle-electrochemical carboxylation), sequential aryl/vinyl radical cyclization-electrochemical carboxylation, sacrificial anode-free electrochemical carboxylation, and the use of supercritical carbon dioxide both as a reaction media and a reagent were also developed. In this personal account, our efforts in and results of electrochemical fixation of carbon dioxide to organic compounds with carbon-carbon bond forming reactions yielding novel and useful carboxylic acids are introduced along with their applications and some new results.

Sustainable glycerol carbonate electrolytes for Li-ion supercapacitors: performance evaluation of butyl, benzyl, and ethyl glycerol carbonates

Substitution of flammable, toxic solvents in electrolytes with alternative green options is of significant commercial and environmental interest.

Divergent Synthesis of Isonitriles and Nitriles by Palladium-Catalyzed Benzylic Substitution with TMSCN.

Ligand-controlled palladium-catalyzed divergent synthesis of isonitriles and nitriles from benzylic carbonates and TMSCN has been developed. The BINAP- or DPEphos-ligated palladium catalyst selectively provides the corresponding benzylic isonitriles, whereas their regioisomers, benzylic nitriles, are formed exclusively under phosphine ligand-free conditions. Mechanistic studies reveal that isonitrile is the primary product under both conditions, but it is isomerized into nitrile in the absence of ancillary phosphine ligands.

Photoredox/palladium-cocatalyzed enantioselective alkylation of secondary benzyl carbonates with 4-alkyl-1,4-dihydropyridines

A photoredox/palladium-cocatalyzed enantioselective alkylation of racemic secondary carbonates with 4-alkyl-1,4-dihydropyridines under visible light irradiation has been developed. The present study provides a method for the preparation of optically active diarylalkanes from racemic diarylmethyl carbonates by a dynamic kinetic asymmetric transformation (DYKAT). This photoredox/palladium dual catalysis strategy expands the scope of the asymmetric Pd-catalyzed benzylic substitution reaction and serves as its potential alternative and complement.

Room-Temperature Benzylic Alkylation of Benzylic Carbonates: Improvement of Palladium Catalyst and Mechanistic Study

The palladium catalyst for the nucleophilic substitution of benzyl carbonates was improved by using 1,1′-bis(diisopropylphosphino)ferrocene (DiPrPF) as the ligand. The [Pd(η3-C3H5)(cod)]BF4–DiPrPF ...

Stable Benzylic (1-Ethynylcyclohexanyl)carbonates Protect Hydroxyl Moieties by the Synergistic Action of [Au]/[Ag] Catalytic System.

Chemical syntheses of oligosaccharides and glycosides call utilization of many protecting groups that can be installed or deprotected without affecting other functional groups present. Benzyl ethers are routinely used in the synthesis of glycans as they can be subjected to hydrogenolysis under neutral conditions. However, installation of benzyl ethers is often carried out under strong basic conditions using benzyl halides. Many a times, strongly basic conditions will be detrimental for some of the other sensitive functionalities (e.g., esters). Later introduced reagents such as benzyl trichloroacetimidate and BnOTf are not shelf-stable, and hence, a new method is highly desirable. Taking a cue from the [Au]/[Ag]-catalyzed glycosidations, we have identified a method that enables protection of hydroxyl groups as benzyl, p-methoxybenzyl, or naphthylenemethyl ethers using easily accessible and stable carbonate reagent. A number of saccharide-derived alcohols were subjected to the benzylation successfully using a catalytic amount of gold phosphite and silver triflate. Furthermore, the protocol is suitable for even protecting menthol, cholesterol, serine, disaccharide OH, and furanosyl-derived alcohol easily. The often-utilized olefins and benzoates, as well as benzylidene-, silyl-, Troc-, and Fmoc-protecting groups do not get affected during the newly identified protocol. Regioselective protection and one-pot installation of benzyl and p-methoxybenzyl ethers are demonstrated.

Cleavage of C–C and C–O Bonds to Form C–C Bonds: Direct Cross‐Coupling between Acetylenic Alcohols and Benzylic Carbonates

A palladium‐catalyzed cross‐coupling reaction between C(sp) and C(sp3) centers was achieved in excellent yields via C–C bond cleavage and C–O bond cleavage. This procedure uses relatively stable acetylenic alcohols as reactants instead of unstable/volatile terminal alkynes. The use of benzylic carbonates also avoids the involvement of benzyl halides, making this method more practical in synthesis. Ligands play an important role in the procedure and K2CO3 accelerates the reaction.

Asymmetric Synthesis of Diarylmethyl Sulfones by Palladium-Catalyzed Enantioselective Benzylic Substitution: A Remarkable Effect of Water.

A Pd/(R)-BINAP-catalyzed enantioselective benzylic sulfonation of diarylmethyl carbonates with sodium sulfinates proceeds to deliver the corresponding chiral diarylmethyl sulfones in good yields with high enantioselectivity. The reaction occurs in a dynamic kinetic asymmetric transformation (DYKAT) manner and thus provides convergent access to optically active benzylic sulfones from racemic secondary benzylic carbonates. Additionally, the addition of H2 O is found to be critical for high enantioselectivity.

Palladium-catalyzed Benzylic Substitution of Benzyl Carbonates with Phosphorus Nucleophiles

A wide range of benzyl carbonates reacted with dimethyl phosphonate or diphenylphosphine oxide in the presence of the palladium catalyst, [Pd(η3-allyl)Cl]2–DPEphos, to give dimethyl benzylphosphonates and benzyldiphenylphosphine oxides in high yields. The catalytic phosphonylation was applied to the one-pot synthesis of alkenes from the benzyl esters.

Selective Synthesis of (Benzyl)biphenyls by Successive Suzuki-Miyaura Coupling of Phenylboronic Acids with 4-Bromobenzyl Acetate under Air Atmosphere.

An efficient Pd-catalyzed cross-coupling reaction of phenylboronic acids and benzyl carbonates was developed, producing diarylmethanes. Benzyl acetates could also be used as coupling partners instead of benzyl carbonates, affording diarylmethanes in comparable yields. This reaction can be conducted under air atmosphere without any care for moisture and oxygen. The ester function showed an intermediate reactivity between chloro and bromo groups. This property facilitated the selective synthesis of diverse (benzyl)biphenyls by successive Suzuki–Miyaura coupling reactions using bromo- and chloro-substituted benzyl esters with two types of boronic acids.

Palladium-Catalyzed Asymmetric Benzylic Substitution of Secondary Benzyl Carbonates with Nitrogen and Oxygen Nucleophiles.

A Pd/(R)-BINAP-catalyzed asymmetric benzylic substitution of secondary benzyl carbonates with amides and amines proceeds to form the corresponding optically active benzylamines in good yields with a high enantiomeric ratio. The reaction occurs in a dynamic kinetic asymmetric transformation (DYKAT) manner. Additionally, the asymmetric Pd catalysis can also be applicable to phenol nucleophiles, thus delivering chiral ethers with acceptable yields and enantioselectivity.

3,4-Alkadienyl ketones via the palladium-catalyzed decarboxylative allenylation of 3-oxocarboxylic acids.

In this communication, we report a palladium-catalyzed decarboxylative allenylation of benzyl carbonates and tert-butyl carbonates of 2,3-allenols with 3-oxocarboxylic acids. The reaction provides a new and straightforward approach to 3,4-dienyl ketones under mild conditions.

ChemInform Abstract: Palladium‐Catalyzed Direct Benzylation of Polyfluoroarenes with Benzyl Carbonates Through Selective C—H Functionalization.

ChemInformVolume 47, Issue 48 Isocyclic Compounds ChemInform Abstract: Palladium-Catalyzed Direct Benzylation of Polyfluoroarenes with Benzyl Carbonates Through Selective C—H Functionalization. Guanghui Yang, Guanghui Yang Collab. Innovation Cent., Zhejiang Univ. Technol., Hangzhou 310014, Peop. Rep. ChinaSearch for more papers by this authorXinpeng Jiang, Xinpeng Jiang Collab. Innovation Cent., Zhejiang Univ. Technol., Hangzhou 310014, Peop. Rep. ChinaSearch for more papers by this authorYong Liu, Yong Liu Collab. Innovation Cent., Zhejiang Univ. Technol., Hangzhou 310014, Peop. Rep. ChinaSearch for more papers by this authorNa Li, Na Li Collab. Innovation Cent., Zhejiang Univ. Technol., Hangzhou 310014, Peop. Rep. ChinaSearch for more papers by this authorGuisen Yin, Guisen Yin Collab. Innovation Cent., Zhejiang Univ. Technol., Hangzhou 310014, Peop. Rep. ChinaSearch for more papers by this authorChuanming Yu, Chuanming Yu Collab. Innovation Cent., Zhejiang Univ. Technol., Hangzhou 310014, Peop. Rep. ChinaSearch for more papers by this author Guanghui Yang, Guanghui Yang Collab. Innovation Cent., Zhejiang Univ. Technol., Hangzhou 310014, Peop. Rep. ChinaSearch for more papers by this authorXinpeng Jiang, Xinpeng Jiang Collab. Innovation Cent., Zhejiang Univ. Technol., Hangzhou 310014, Peop. Rep. ChinaSearch for more papers by this authorYong Liu, Yong Liu Collab. Innovation Cent., Zhejiang Univ. Technol., Hangzhou 310014, Peop. Rep. ChinaSearch for more papers by this authorNa Li, Na Li Collab. Innovation Cent., Zhejiang Univ. Technol., Hangzhou 310014, Peop. Rep. ChinaSearch for more papers by this authorGuisen Yin, Guisen Yin Collab. Innovation Cent., Zhejiang Univ. Technol., Hangzhou 310014, Peop. Rep. ChinaSearch for more papers by this authorChuanming Yu, Chuanming Yu Collab. Innovation Cent., Zhejiang Univ. Technol., Hangzhou 310014, Peop. Rep. ChinaSearch for more papers by this author First published: 10 November 2016 https://doi.org/10.1002/chin.201648073Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume47, Issue48November, 2016 RelatedInformation

Palladium‐Catalyzed Direct Benzylation of Polyfluoroarenes with Benzyl Carbonates through Selective C−H Functionalization

AbstractA novel and efficient palladium‐catalyzed cross‐coupling benzylation reaction of pentafluorobenzene through selective C−H functionalization has been developed. A series of carbonates and polyfluorobenzenes have been examined and found to give moderate to good yields. This transformation provides a new straightforward approach for the synthesis of fluorinated diarylmethanes.

ChemInform Abstract: An Improvement of the Palladium‐Catalyzed [4 + 2] Cycloaddition of o‐(Silylmethyl)benzyl Carbonates with Alkenes.

AbstractTris(4‐methoxy‐3,5‐dimethylphenyl)phosphane is evaluated as the ligand in hitherto unsuccesful Pd‐catalyzed transformations to substituted 1,2,3,4‐tetrahydronaphthalenes.