Furan Ring-opening Reaction Research Articles

Enhancing the ketonization efficiency of biomass through selective conversion of furanic compounds

Catalytic ketonization of biomass is an effective approach for the deoxygenation of bio-oil and the enrichment of high-purity ketone products. However, the bio-oil contains a large amount of furanic components with oxygenated side groups (e.g., furfural, furfuralcohol, etc.), which severely hinders the efficiency of the ketonization reaction. In response to this challenge, this study employed Pd-based catalysts for selective conversion of furfural into "keto-friendly" components, thereby mitigating their inhibitory effects. Initially, three morphologies of CeO2 (the main catalyst for ketonization) were selected to investigate their influence on furfural conversion. It was found that the products were mainly furfural (exceeding 86 %), with only up to approximately 13 % of "keto-friendly" products (mainly furans) detected, indicating that pure CeO2 exhibits a weak catalytic effect on the effective conversion of furfural. Compared with pure CeO2, the yield of "keto-friendly" products increased significantly when 1 wt% Pd was loaded, demonstrating the excellent catalytic performance of Pd in the effective conversion of furfural. Co-doping of Pd and Zr (5 wt%) on CeO2 further increased the "keto-friendly" products to 66 %, suggesting a synergistic effect of Pd and Zr. Mechanism analysis revealed that Pd promotes the formation of furans and benzenes by enhancing the decarbonylation of furfural and subsequent furan ring opening reactions, while the competing carbonyl hydrogenation pathway is weakened. The findings of this study will be beneficial for enhancing the biomass ketonization conversion, thereby providing valuable references for the high-value utilization of biomass.

Hydrodeoxygenation of C15 furanic precursor over mesoporous NiMo-ZrO2 composite catalysts for the production of sustainable aviation fuel

Sustainable aviation fuel (SAF) is essential for achieving carbon neutrality in the transportation sector. This study elucidates the production of SAF range C9-C15 branched alkanes by hydrodeoxygenation (HDO) of C15 furanic precursor derived from 2-methylfuran and furfural via hydroxyalkylation-alkylation reaction. HDO reaction was performed using high surface area mesoporous NiMo-ZrO2 composite catalysts that exhibited high selectivity to central SAF alkanes (C13-C14). Deoxygenation follows a complex reaction network involving furanic double bond saturation and furan-ring opening reactions in series, followed by the cascade of HDO, dehydroformylation, and C-C bond cleavage. The present investigation enlightens the impact of calcination temperatures and metal (Mo and Ni) contents on structural stability, physicochemical properties, and catalytic performance of NiMo-ZrO2. Both Ni and Mo stabilized the tetragonal ZrO2 phases with improved surface area. The catalytic activity proliferated with rising calcination temperature till 873 K due to the enrichment of Mo-O-Zr acidic species and deteriorated beyond this temperature owing to the generation of crystalline MoO3/Zr(MoO4)2 species. NiMo alloy formation was enhanced, and concurrently, acidity was reduced with increasing Mo content. 30 wt% MoO3-containing catalyst showed the best catalytic activity due to the proper balance between acidity and NiMo alloy. Oxygenate conversion was boosted by increasing NiO addition up to 15 wt% due to the enhanced Ni and NiMo alloy formation and decreased at 20 wt% owing to the evolution of catalytically inactive bulk metal oxide species. Catalytic cracking was prominent at elevated reaction temperatures, with significant amounts of C13 alkane.

Tuning conditions for the amine-functionalization of carbonyls formed in biobased polyfurfuryl alcohol

Biobased furan resins (furfuryl alcohol based) are functionalized by taking advantage of a side-reaction occurring during its polymerization. The furan ring-opening reactions yields carbonyls which can be functionalized by reaction with primary amines. Light is shed on unexplored parameters impacting the properties of PFA/Amine systems. First, PFA/Amines were prepared using PFA resins at conversion degree between 0.3 and 0.95. Overall, high conversion degrees (0.9 and above) are best suited to produce rigid materials. In addition, a precipitation process may be used to reach high Tg biobased materials (145 °C). Finally, the impact of the amines’ basicity on the properties of PFA/Amines was investigated. The results highlighted that PFAs at conversion degrees above 0.9 are little affected by the basicity. However, the properties of PFA functionalized at lower conversion degrees are strongly affected by the bases, i.e. high brittleness. This can be circumvented by limiting the functionalization degree to 0.25 and below.

Selective control of donor-acceptor Stenhouse adduct populations with non-selective stimuli

Selective control of donor-acceptor Stenhouse adduct populations with non-selective stimuli

Revealed pathways of furan ring opening and surface crosslinking in biobased polyfurfuryl alcohol

Poly(furfuryl alcohol) – (PFA) is a biobased thermoset known for its highly crosslinked structure. Bidimensional NMR (2D-NMR) was employed to give new insights on the complex structural organization in PFA with a special emphasis on the side structures resulting from furan ring-opening. Interestingly, the presence of aldehyde functions was for the first time clearly highlighted and quantified in PFA resins. Overall, the aldehydes account for about 20 % of the total carbonyls present in PFA. Results from HSQC and HMBC sequences allowed proposing two pathways for the furan ring opening reactions. The first one is an hydrolytic-ring opening leading to levulinic like species. The second one is rather an oxidative furan-ring opening leading to conjugated aldehydes. These conjugated aldehydes are prone to crosslink via Diel-Alder cycloadditions with furanic entities thus leading to crosslinking. At macroscopic scale, this newly proposed crosslinking pathway would explain the formation of the rigid shell formed at the external surfaces of PFA resins.

Furan ring opening reaction for the synthesis of 2,5-dicarbonyl-3-ene-phosphates.

Furan ring opening reactions are essential in organic synthesis, enabling the incorporation of diverse functional groups and the construction of complex molecular structures. A highly efficient and practical method for synthesizing 2,5-dicarbonyl-3-ene-phosphates from readily available biomass furan and dialkyl phosphonates is reported. The reaction, catalyzed by FeCl3, demonstrated wide substrate scope and high synthetic efficiency. Gram-scale synthesis was achieved, and a one-pot reaction provided a quick access route to the desired compounds. Additionally, a successful Diels-Alder reaction highlighted the versatility of the methodology.

Production of green jet fuel from furanics via hydroxyalkylation-alkylation over mesoporous MoO3-ZrO2 and hydrodeoxygenation over Co/γ-Al2O3: Role of calcination temperature and MoO3 content in MoO3-ZrO2

Green biofuels are equivalent to hydrocarbon-based motor fuels and compatible with existing refinery infrastructures and combustion engines. Therefore, sustainable production of green biofuels is essential to circumvent the construction of expensive biorefinery infrastructures. This study thus presents the production of green jet fuel from biomass-derived furanic compounds via hydroxyalkylation-alkylation (HAA) reaction coupled with hydrodeoxygenation (HDO) of the C15 biofuel precursor. MoO3-promoted ZrO2 is a promising solid acid catalyst with excellent thermal stability. The HAA reaction of 2-methylfuran with furfural was thus investigated over a novel MoO3-promoted mesoporous ZrO2 catalyst. This work elucidated the role of calcination temperature and MoO3 loading on the structural variation of MoO3-promoted mesoporous ZrO2 and the evolution of acid sites. The highest acid density and consequently best catalytic performance was observed at 873 K calcination temperature with 20 wt% MoO3 loading. About 85 % 2-methylfuran conversion was achieved over 1.25 g of this optimum catalyst at 2:1 2-methylfuran/furfural mole ratio, 323 K, and 5 h. The HAA reaction was further investigated at various reaction temperatures, catalyst loadings, and 2-methylfuran/furfural mole ratios to obtain optimum reaction conditions. HDO of biofuel precursor was examined over Co/γ-Al2O3 catalyst at various reaction temperatures, initial hydrogen pressure, and Co metal loading on γ-Al2O3 to understand the reaction mechanism and identify the optimum reaction conditions. HDO of biofuel precursor progressed through successive furan ring saturation and opening reactions, followed by a combination of HDO, decarbonylation, and cleavage of tertiary-carbon bonds. C9-C15 alkanes were observed as products, with C11 and C14 hydrocarbons being dominant at 573 K and 30 bar. The elevated hydrogen pressure and reaction temperature boosted the conversion of oxygen-containing intermediate compounds at the cost of CC cracking reactions. The conversion of oxygen-containing intermediate compounds was enhanced with rising Co metal loading on γ-Al2O3 up to 20 wt% due to the enhancement of metal dispersion.

Properties of a furan ring-opening reaction in aqueous micellar solutions for selective sensing of mesalazine

A novel and efficient non-azo formation based method was developed for trace sensing of mesalazine (MES), a pharmaceutical aromatic amine. MES was simply coupled with a Meldrum’s activated furan (MAF) reagent via a furan ring opening reaction to form a colored product. The intense purple colored solution was detected at 575 nm. The reaction of MES with MAF was monitored by employing 1H NMR spectroscopy and mass spectrometry. In addition, density functional theory (DFT) was applied to optimize the structure of the colored product and its λmax (the wavelength of maximum absorbance) in dimethyl sulfoxide and water. The colored product was considered in three possible structures, and the most possible structures in dimethyl sulfoxide and in water were identified by employing the DFT calculations. Both of the most possible structures indicated only a local excitation in their λmax and no charge transfer was observed. However, one of the structures in dimethyl sulfoxide presented charge transfer properties occurring through NCCC moiety. A univariate optimization method was also used to attain the optimum condition for analysis. In addition, the dependence of the analytical response on the three main affecting parameters (reaction time (X1), Triton X-100 concentration (X2) and MAF concentration (X3)) was identified by employing a central composite design (CCD) approach. The CCD study showed that the analytical response depends complexly on the parameters. Beer’s law was obeyed within the range of 0.06–9.30 μg mL−1 of MES (155 fold linearity) at 575 nm, under the optimum condition introduced by the CCD approach. Also, the limit of detection was obtained 0.04 μg mL−1 of MES. The method showed precision (as relative standard deviation) and accuracy (as recovery) within the ranges of 0.6–3.2 % and 96.3–100.8%, respectively. Various organic and inorganic species, amino-pharmaceuticals, and amino acids were tested to evaluate the selectivity of the method. The selectivity of the analytical method was satisfactory. The method was successfully applied for detection of MES in various water matrices and pharmaceutical tablets.

Characterization of lignans in Forsythiae Fructus and their metabolites in rats by ultra-performance liquid chromatography coupled time-of-flight mass spectrometry

This study was designed to profile the chemical information of Forsythiae Fructus (FF) and investigate the in-vivo FF-related xenobiotics, especially for lignans. Rats were oral administrated of FF and pinoresinol-4-O-glucoside, respectively. Blood and urine samples were collected after ingestion, and xenobiotics was profiled by an UPLC/Qtof MS method. A total of 19 lignans were identified or tentatively characterized in FF, and 63 lignan-related xenobiotics were found in rat plasma and urine after ingestion of FF. It was found that lignans could be transformed into metabolites by furan ring opening, hydrogenation, demethylation, dehydration and phase II reactions (sulfation and glucuronidation). The whole metabolic behaviour of bisepoxylignan was revealed by evaluating the metabolism of pinoresinol-4-O-glucoside in vivo. It was found that the configuration of C-8/C-8' was retained after furan ring opening and metabolic reactions always occurred at position of C-3/C-4/C-5 or C-3'/C-4'/C-5'. Additionally, other types components in FF and in vivo were also characterized. This work revealed the in-vivo metabolism of FF, and reported the characteristic metabolic reactions of lignans for the first time. It was also provided the foundation for the further investigation on pharmacodynamic components of FF or TCMs containing FF.

Mechanism of Pd/C-catalyzed hydrogenation of furfural under hydrothermal conditions

Catalytic hydrogenation of furfural under hydrothermal conditions is of great importance and has recently attracted huge attention as an approach to obtaining a wide range of valuable chemicals from a renewable source. However, the data concerning the reaction mechanism of aqueous-phase furfural hydrogenation are very scarce, and it is still not clear which reactions lead to various carbonyl compounds, such as cyclopentanone, 4-oxopentanal, 5-hydroxy-2-pentanone. Herein, we present the results of an experimental study of the mechanism of reactions occurring in the furfural hydrogenation under hydrothermal conditions over the 1% Pd/CNTs catalyst. The following approaches have been used to study the reaction mechanism: hydrogenation of key intermediates formed upon the furfural conversion, and isotopic labeling experiments using D2O as a tracer in hydrogenation of furfural, which provides direct evidence of the occurring reactions. It was found that the furfural hydrogenation process is realized through four pathways including various reductive and acid-catalyzed furan ring opening reactions. The methods and approaches used in the present work, as well as the results obtained, can be useful in studying the mechanism of aqueous-phase hydrogenation of a wide range of oxygen-containing substrates in the presence of catalysts of different compositions.

Mechanistic understanding of humin formation in the conversion of glucose and fructose to 5-hydroxymethylfurfural in [BMIM]Cl ionic liquid.

Humin formation is one of the key issues that hinders economical 5-HMF production from hexose sugars such as glucose and fructose. In this work, the mechanism of humin formation in glucose/fructose conversion to HMF was studied in an ionic liquid system (1-butyl-3-methylimidazolium chloride, [BMIM]Cl) with CrCl3 as the catalyst. Elemental analysis, XRD, FT-IR, and TEM were applied to study the molecular structure and morphology of the solid humins. The possible intermediates to form solid humins were investigated by HPLC-MS. We synthesized furanic model compounds that mimic the experimentally identified humin intermediates to investigate the mechanism of humin growth at an early stage. The results showed that a furan compound bearing a hydroxymethyl and an electron-donating group was unstable due to three types of reactions: (1) bimolecular ether formation reactions; (2) intermolecular addition reaction; (3) furan ring opening reaction with water. The stability of a furan compound in [BMIM]Cl was increased when the hydroxymethyl group of a furan compound was protected by a methyl group, and the stability was further enhanced with an additional electron-withdrawing group (such as an aldehyde group) on the furan ring. Protecting the hydroxymethyl group of 5-HMF with a methyl group allows easy separation of the products from the [BMIM]Cl solvent through extraction.

A First-Principles Investigation of Gas-Phase Ring-Opening Reaction of Furan over HZSM-5 and Ga-Substituted ZSM-5

The furan ring-opening reaction using three catalytic models, HZSM-5, the extra-framework sites [GaO]/ZSM-5, and [Ga(OH)2]/ZSM-5, was investigated using periodic density functional theory as a mode...

Opening Furan for Tailoring Properties of Bio-based Poly(Furfuryl Alcohol) Thermoset.

This work shows how furan ring-opening reactions were controlled by polymerization conditions to tune the cross-link density in bio-based poly(furfuryl alcohol) (PFA). The influence of water and isopropyl alcohol (IPA) on the polymerization of furfuryl alcohol, and particularly on furan ring-opening, was investigated by means of 13 C NMR and FT-IR spectroscopy. Results indicated that formation of open structures were favored in the presence of solvents, thus leading to modification of the thermo-mechanical properties compared to PFA cross-linked without solvent. Dynamic mechanical analyses showed that when slightly more open structures were present in PFA it resulted in an important decrease of the cross-link density. Despite lower glass-transition temperature and lower elastic modulus for PFA polymerized with solvent, the thermal stability remains very high (>350 °C) even with more open structures in PFA.

Monitoring conical intersections in the ring opening of furan by attosecond stimulated X-ray Raman spectroscopy.

Attosecond X-ray pulses are short enough to capture snapshots of molecules undergoing nonadiabatic electron and nuclear dynamics at conical intersections (CoIns). We show that a stimulated Raman probe induced by a combination of an attosecond and a femtosecond pulse has a unique temporal and spectral resolution for probing the nonadiabatic dynamics and detecting the ultrafast (∼4.5 fs) passage through a CoIn. This is demonstrated by a multiconfigurational self-consistent-field study of the dynamics and spectroscopy of the furan ring-opening reaction. Trajectories generated by surface hopping simulations were used to predict Attosecond Stimulated X-ray Raman Spectroscopy signals at reactant and product structures as well as representative snapshots along the conical intersection seam. The signals are highly sensitive to the changes in nonadiabatically coupled electronic structure and geometry.

Use of 5-formylfuranboronic acid in the formation of bicyclic boronates with photophysical properties

Treatment of 5-formyl-2-furanboronic acid with 2-aminophenol 4,5-(R)substituted (R=–Cl, –NO2, –CH3, –CO2H, naphtyl) offers bicyclic boronates, in which a furan ring-opening reaction is involved. Even though the reaction proceeds in all cases, lower yields were obtained when aminophenol derivatives include electron withdrawing substituents. Evaluation of the photophysical properties for all compounds showed substantial solvatochromic and luminescent changes. The solvatochromic effect was clear noticed from changes in color solutions from solvents with different polarities/polarizabilities and hydrogen bonding capacities. Influence of the substituents is also appreciable at the absorption and emission spectra, in where the nitro derivatives showed poor absorbance and emission bands. In addition, computational NLO properties were calculated which showed β values from 29 to 139×10−30cm5esu−1, showing thus possible applications as optoelectronic materials.

Isolation and characterization of luminescent bicyclic boronates based on furan ring-opening reactions from 5-formyl-2-furanboronic acid

A new family of luminescent boronates was prepared from reaction of 5-formyl-2-furanboronic acid with 2-aminophenol derivatives. The furan ring-opening was favored by the presence of the boronic acid group. Evaluation of the photophysical characteristics for all compounds showed significant solvatochromic, fluorescent, and NLO properties.

Novel Synthesis of Benzalacetone Analogues of Naphth[a]azulenes by Intramolecular Tropylium Ion-Mediated Furan Ring-Opening Reaction and X-ray Investigation of a Naphth[1,2-a]azulene Derivative

[reaction: see text] Benzalacetone analogues of naphth[1,2-a]azulene (8), naphth[2,1-a]azulene (13), and naphth[2,3-a]azulene (18) were synthesized from 2-(5-methyl-2-furyl)-1-tropylionaphthalene (7), 1-(5-methyl-2-furyl)-2-tropylionaphthalene (12), and 2-(5-methy-2-furyl)-3-tropylionaphthalene (17), respectively. The synthetic method is based on furan ring-opening reaction by the intramolecular electrophilic attack of a tropylium ion. Single-crystal X-ray work on the naphth[1,2-a]azulene derivative (8) revealed that its tetracyclic system exhibited deformation from planarity similar to that of benzo[c]phenanthrene (tetrahelicene). A centrosymmetric associated dimer structure, just like the molecules of carboxylic acids but via C=O...H-C hydrogen bonds, was found in the crystal. Reduction of bond-length alternation in the seven-membered ring was also found.

An efficient novel synthesis of beta-(azuleno[1,2-b]benzothienyl)- and beta-(azuleno[2,1-b]benzothienyl)-alpha,beta-unsaturated ketones by the tropylium ion-mediated intramolecular furan ring-opening reaction and X-ray investigation of methyl ketone derivative.

Intramolecular reaction of 2-tropylio-3-(5-substituted 2-furyl)benzothiophenes (3), prepared from the corresponding 2-cycloheptatrienyl-3-(5-substituted 2-furyl)benzothiophenes (2), afforded the beta-(azuleno[1,2-b]benzothienyl)-alpha,beta-unsaturated ketones (4), which are otherwise difficult to obtain, in moderate yields. The reaction involves a ring-opening process of the furan ring by intramolecular attack of the tropylium ion onto the 2-position of the furan ring. Similarly, beta-(azuleno[2,1-b]benzothienyl)-alpha,beta-unsaturated ketones (8) were obtained from the corresponding 3-tropylio-2-(5-substituted 2-furyl)benzothiophenes (7) albeit in lower yields. The molecular and crystal structures of the methyl ketone derivative, 8a, are discussed on the basis of X-ray structure analysis.

Furan Ring Opening Reactions in Heterocycle Synthesis

AbstractFor Abstract see ChemInform Abstract in Full Text.

Novel and Facile Synthesis of β‐(4‐Azuleno[1,2‐b]thienyl)‐ and β‐(4‐Azuleno[2,1‐b]thienyl)‐α,β‐unsaturated Ketones by Intramolecular Tropylium Ion Mediated Furan Ring Opening Reaction.

The novel and efficient methods for the synthesis of β-(4-azuleno[1,2-b]thienyl)-α,β-unsaturated ketones (1) and β-(4-azuleno[2,1-b]thienyl)-α,β-unsaturated ketones (2) have been described. Refluxing the dichloromethane solutions of 2-tropylio-3-(2-furyl)thiophene tetrafluoroborates (3) or 3-tropylio-2-(2-furyl)thiophene tetrafluoroborates (4) afforded (1) and (2), respectively, in moderate yields. The reaction involves an intramolecular tropylium ion-mediated furan ring-opening reaction.