Isomeric Products Research Articles

Non-waste energy and resource-saving heterogeneous catalytic methods of obtaining and transformation of cyclic acetalies and gem-dichlorocyclopropanes

New methods and ways of using heterogeneous zeolite catalysts – H-Y, H-Beta, H-MOR, H-ZSM-5 and micro- meso-porous – H-Ymmm and others in organic synthesis were studied. Using the example of available petrochemical compounds such as polyols, olefins, and dienes, the possibilities of carrying out cyclization and condensation reactions in the presence of zeolites of various structural types are shown. It has been established that the H-Beta zeolite catalyst provides a quantitative yield of ethers and esters during the interaction of olefins – substituted vinyl-gem-dichlorocyclopropanes – with linear alcohols and acids, respectively. It has been determined that the condensation of styrene and an equimolar mixture of 4-hydroxymethyl-1,3-dioxolane and 5-hydroxy-1,3-dioxane in the presence of the H-Beta catalyst proceeds with the formation of ethers, while the ratio of 5 and 6-membered isomeric products = 1.2:1. Multicomponent condensations successfully proceed in one stage in the presence of wide-pore zeolites.

Rapid synthesis of conjugated linoleic acid from fruit processing residues seed oil by alkali‐dimethyl sulfoxide isomerization

AbstractRapid synthesis of conjugated linoleic acid (CLA) by the alkali‐dimethyl sulfoxide (DMSO) isomerization method is presented in this study. Seeds from fruit processing residues in Thailand were screened as an alternative potential source of linoleic acid (LA)‐rich oil. Passion fruit with 72.10% LA and 26.18% oil in the seeds was selected as starting oil. The Alkali‐DMSO isomerization was carried out by mixing DMSO with alkali hydroxides and polyhydric alcohols. Under a mass ratio of 1:0.5:1:1 oil/NaOH/propylene glycol/DMSO, at 180°C, production of the major isomers of CLA (c9,t11, and t10,c12) was complete within 3 min, resulting in a 20‐fold increase in productivity compared to the conventional method. The reaction time decreased because of an increment in the basic strength of the alkali‐DMSO catalyst. CLA from alkali‐DMSO isomerization and commercial supplements showed a similar isomer distribution and yielded similar CC50 values when evaluated against the Vero cell line. This method might be an alternative in industrial production as it is fast and simply applied to the conventional system. In addition, seed oils from fruit processing residues can be used as an alternative to traditional LA‐rich oils.

Divergent Synthesis of Alternant Bisanthenequinone and Nonalternant Heptalenodifluorenedione Ring Systems via a Concentration-Dependent Rearrangement.

The synthesis of a diol containing a nonalternant aromatic core was investigated to access a nonalternant isomer of bisanthene with functional groups suitable for two-dimensional polymerization. An alternant diol and its nonalternant isomer were prepared in a short synthetic route from the same bifluorenylidene starting material. The bifluorenylidene reactant undergoes a Stone-Wales rearrangement in neat triflic acid, which unexpectedly provided both an alternant and nonalternant dione. The rearrangement was characterized by spectroscopy and single crystal X-ray diffraction of Grignard addition products of both isomers. The relative yield of the rearranged, alternant product increased along with the initial concentration of its polycyclic aromatic hydrocarbon (PAH) precursor, implicating a bimolecular rearrangement mechanism and enabling the divergent synthesis of both the nonalternant and alternant products. These findings offer convenient access to functional derivatives of two PAH classes of interest for their optoelectronic properties and serve as yet another warning about the importance of characterizing these materials with care, especially when insoluble products must be carried forward in a multistep synthetic route.

Synthesis of new photo-cured phosphorus-containing oligoestermethacrylates with a spacer in the structure

Objectives. To synthesize phosphorus-containing oligoestermethacrylates spatially separated by spacers of aliphatic or aromatic structure and evaluate their effect on photocuring kinetics.Methods. For determining the qualitative and quantitative composition of the synthesized compounds, the following methods were used: thin layer chromatography; chromatographic and mass spectrometry; infrared spectroscopy; 1H, 13C, 31P nuclear magnetic resonance spectroscopy; differential scanning calorimetry. The dielectric loss tangent was determined on a specially designed optical cell with an ultraviolet (UV) light source to an immittance meter. Elemental analysis was performed on an energy dispersive X-ray fluorescence spectrometer.Results. Spatially separated oligoestermethacrylates based on phosphorus trichloride containing aliphatic or aromatic spacers in the structure were synthesized. During the interaction of glycidyl methacrylate with phosphorus trichloride in the mass of the latter, reaction products were shown to be formed both according to the Krasusky rule from the side of the α-carbon atom, as well as against this rule with the formation of isomeric products. Obtaining these compounds in bulk is possible only in the presence of a homopolymerization inhibitor. The influence of the spacer structure on the curing rate of oligoestermethacrylates under the action of UV radiation has been established. It has been shown that the introduction of a spacer into the oligomer structure is accompanied by an increase in the induction period by a factor of 39 compared to a sample without a spacer.Conclusions. The results obtained indicate the possibility of obtaining new oligoestermethacrylates with aliphatic and aromatic spacers in the structure. The influence of the structure of the spacer on the kinetics of photocuring is determined.

In‐situ Synthesis of Gallium‐Containing SAPO‐11 Molecular Sieves and Superior Catalytic Performance of Their NiWS Supported Catalysts for Hydroisomerization of n‐Hexadecane

AbstractIn order to prepare a high‐performance SAPO‐11 (silicoaluminophosphate‐11) based non‐noble metal supported catalyst for the hydroisomerization of long‐chain n‐alkanes, gallium‐modified SAPO‐11 molecular sieve was successfully synthesized by the in‐situ synthesis method, and the NiWS supported catalyst was prepared for the hydroisomerization of n‐hexadecane. The effects of Ga‐modification on the physicochemical properties of SAPO‐11 molecular sieve, the active phase properties, and the catalytic performance of the catalyst were studied. Through a series of physicochemical characterizations, it was found that the introduction of Ga increased the mesoporous volume of SAPO‐11 molecular sieve, reduced their acid density and strength, but improved the amount of medium‐strong Brønsted acid. The Ga‐modification weakened the interaction between the active metals and the support, increased the sulfidation degree of active metals, and increased the stacking number and dispersion of active phase. The results of catalytic performance evaluation showed that the catalytic activity and isomerization selectivity of the Ga‐modified SAPO‐11 molecular sieve based catalysts were improved, and the yield of i‐hexadecane of NiW/2Ga‐SAPO‐11 was the highest, which was 40.30 % higher than that of NiW/SAPO‐11. By analyzing the distribution of isomeric products, it was found that the Ga‐modified SAPO‐11 molecular sieve was helpful in improving the hydroisomerization depth of n‐hexadecane over the catalyst.

Study of the stability of Ricinodendron heudelotii oil: Effects of solar radiation on the chemical composition of the oil

The native crude oil of Ricinodendron heudelotii mainly consists of triglycerides formed typically with polyunsaturated fatty acids (84%). Fatty acids with three conjugated double bonds (Conjugated Linolenic Acids, CLnA) contain more than 60% of α-eleostearic acid (C18:3 9c, 11 t, 13 t). The heat-treating process using the traditional hulling method of seeds for kernel consumption results in the isomerization of α-eleostearic acid into β-eleostearic and catalpic acid. In order to gather information about the transformation of these conjugated polyunsaturated fatty acids, a study to investigate the effects of solar radiation on the native oil was conducted. Changes in the chemical composition of fatty acids in the oil, especially conjugated polyunsaturated fatty acids, were monitored by GC (Gas Chromatography). Analysis of fatty acid profiles of treated and untreated oils showed the isomerization of α-eleostearic acid under the effect of solar radiation, whether natural or artificial. This isomerization involves the conversion of α-eleostearic acid into its isomers β-eleostearic acid (C18:3 9 t, 11 t, 13 t) and catalpic acid (C18:3 9 t, 11 t, 13c) with a ratio of 5:1 in the triglycerides of the oil. Our findings highlight the significant influence of solar radiation on composition and isomerization of the fatty acids of Ricinodendron heudelotii oil, and emphasize as well as its potential use in the industrial production of some CLnA isomers.

Mitotic phosphorylation inhibits the Golgi mannosidase MAN1A1.

N-glycans are processed mainly in the Golgi, and a well-organized Golgi structure is required for accurate glycosylation. However, during mitosis the Golgi undergoes severe fragmentation. The resulting trafficking block leads to an extended exposure of cargo molecules to Golgi enzymes. It is unclear how cells avoid glycosylation defects during mitosis. In this study, we report that Golgi α-1,2-mannosidase IA (MAN1A1), the first enzyme that cargo proteins encounter once arriving the Golgi, is phosphorylated at serine 12 by CDK1 in mitosis, which attenuates its activity, affects the production of glycan isomers, and reduces its interaction with the subsequent glycosyltransferase, MGAT1. Expression of wild-type MAN1A1, but not its phosphomimetic mutant, rescues the glycosylation defects in mannosidase I-deficient cells, whereas expression of its phosphorylation-deficient mutant in mitosis increases the formation of complex glycans. Our study reveals that glycosylation is regulated by cytosolic signaling during the cell cycle.

Structure Identification for Force-Induced Reaction Using Single-Molecule Conductance Measurement

Structure Identification for Force-Induced Reaction Using Single-Molecule Conductance Measurement

Preliminary Microbiological Tests of S-Carvone and Geraniol and Selected Derivatives of These Compounds That May Be Formed in the Processes of Isomerization and Oxidation.

This work presents a literature review on the biological activity of S-carvone, geraniol and derivatives of these compounds, which are formed in the process of isomerization (during the process of geraniol isomerization, oxidation products of this compound are also obtained). Moreover, this work presents preliminary microbiological tests of creams with the addition of these biologically active compounds: S-carvone, geraniol, carvacrol (an S-carvone isomerization product), nerol (a geraniol isomerization product), linalool (a geraniol isomerization product) and citral (a geraniol oxidation product). Because the post-reaction mixture obtained after the S-carvone isomerization has a relatively simple composition, it was also added to creams and tested without isolating pure compounds. This may be a cheaper alternative to creams prepared with the addition of pure compounds. The mixture obtained after the geraniol isomerization process has a very complex composition; therefore, only compounds with the lowest molecular weight and are easily commercially available were selected for studies. The content of the tested compounds in the creams ranged from 0.5 to 3 wet%. The following microorganisms were selected for microbiological tests: the Gram-negative bacterium Escherichia coli K12, the Gram-positive bacterium Staphylococcus epidermidis, and the fungi Candida albicans, Trichophyton rubrum, Aspergillus niger, and Penicillium chrysogenum. A content of 3% carvacrol, nerol, geraniol and citral inhibited the growth of E. coli, and attenuated the growth of C. albicans and T. rubrum. On the other hand, 3% carvacrol and citral only poorly attenuated the growth of the mould fungi P. chrysogenum and A. niger.

Influence of Metal Coordination on the Gas-Phase Chemistry of the Positional Isomers of Fluorobenzoate Complexes.

The fragmentation behaviors of the o-, m-, and p-fluorobenzoate complexes of La3+, Ce3+, Fe3+, Cu2+, and UO22+ were investigated by electrospray ionization mass spectrometry, and the corresponding reaction mechanisms were explored by density functional theory (DFT) calculations. Fluoride transfer product LaIIIFCl3-/CeIIIFCl3- and decarboxylation product LaIIICl3(C6H4F)-/CeIIICl3(C6H4F)- were observed when the carboxylate precursors LaIIICl3(C6H4FCO2)-/CeIIICl3(C6H4FCO2)- were subjected to collision-induced dissociation. The variation in product ratios, which is not obvious in the meta and para cases, qualitatively follows the increasing overall energy barrier and reaction endothermicity of the two-step CO2/C6H4 elimination mechanism, and this aligns with the increase in U-F distance in the ortho, meta, and para decarboxylation product isomers. In contrast, the mass spectra of FeIIICl3(C6H4FCO2)-/CuIICl2(C6H4FCO2)- are dominated by the reduction product FeCl3-/CuCl2- regardless of the fluorobenzoate isomer. DFT/B3LYP calculations show that the two-step CO2/C6H4F elimination pathways are comparable in energy for all three positional isomers. It is energetically more favorable to give the reduction product than the fluoride transfer product, which is opposite to the lanthanum cases. Although the decarboxylation product was observed for all three UVIO2Cl2(C6H4FCO2)- isomers, the ortho isomer behaves more similarly to LaIIICl3(C6H4FCO2)-/CeIIICl3(C6H4FCO2)- as evidenced by the formation of UVIO2FCl2-, and the appearance of UVO2Cl2- in the cases of the meta and para isomers indicates the similarity with FeIIICl3(C6H4FCO2)-/CuIICl2(C6H4FCO2)-. The shorter U-F distance in UVIO2Cl2(o-C6H4F)- causes the decrease in the fluoride transfer barrier and thus makes this process more favorable over o-C6H4F radical loss to give UVO2Cl2-.

Functional characterization of secologanin synthase-like homologous genes suggests their involvement in the biosynthesis of diverse metabolites in the secoiridoid biosynthetic pathway of Camptotheca acuminata Decne

The assignment of functions based on homology has recently been challenged by the frequent discovery of functional divergence among homologous gene family members of enzymes involved in plant secondary metabolism. Secologanin synthase (SLS) is the key CYP450 enzyme that acts critically in the biosynthesis of Strychnos alkaloid scaffold. In this study, to fully elucidate the mechanism that underlies metabolic variation, the CYP450 paralogs that participate in oxidative transformation of the secoiridoid pathway were functionally characterized by combining multitiered strategies of metabolite profiling, phylogenetic analyses, biochemistry assays and reverse genetics techniques. Five CaSLSs-like homologous genes were mined and isolated from an integrative multi-omics database of Camptotheca acuminata. Protein sequences, structural comparisons, and phylogenetic analyses confirmed that CaSLS1–2 and CaSLS4–5 were grouped into the SLS clade, and only CaSLS3 clustered into the 7DLH clade. Five homologs, including two previously identified enzymatic genes, were thus designated as CaSLAS1, CaSLAS2, Ca7DLH, CaSLS4 and CaSLS5. Enzymatic assays of the recombinant proteins in yeast showed that CaSLAS1 and CaSLAS2 displayed multi-catalytic activities of SLS, secologanic acid synthase (SLAS) and secoxyloganin synthase (SXS). Additionally, the reactions of CaSLASs enzymes generated stereospecific isomers of secoiridoid products, and a new product of secoxyloganin was observed. CaSLS5, a third SLS enzyme isoform that catalyzes the formation of secologanin, was reported for the first time. However, CaSXS enzymatic activities in vitro had little physiological impact on the biosynthesis of camptothecin (CPT) in Camptotheca acuminata. The primary and secondary roles of CaSLSs-like genes in secoiridoid metabolism were confirmed by virus-induced gene silencing (VIGS) in plant leaves. Efficient silencing and transcriptional downregulation of CaSLAS2, compared with the CaSLAS1 homologs, resulted in a greater reduction of the accumulation of CPT within silenced plants, and CaSLS5 had barely any effect on the contents of metabolites in planta. Thus, CaSLAS2, rather than CaSLAS1, appeared to function as a major participant in the biosynthesis of CPT, and there were redundant functions in the CaSLSs-like enzymes. Consistent with such roles, CaSLAS2 was ubiquitously expressed at very high levels in Camptotheca tissues, and CaSLAS2 was specifically expressed in young leaves. In contrast, CaSLS5 was poorly expressed in every tissue tested. Our findings demonstrate that homologs that belong to the CYP72 gene family are functionally diverse and exhibit divergence and thereby uncover an expanding group of enzymatic genes that determine the chemo-diversity of the iridoid pathway.

Chemoenzymatic Synthesis of Optically Active Ethereal Analog of iso-Moramide-A Novel Potentially Powerful Analgesic †.

To develop potent and safer analgesics, we designed and synthesized a novel enantiomerically enriched ethereal analog of (R)-iso-moramide, namely 2-[(2R)-2-(morpholin-4-yl)propoxy]-2,2-diphenyl-1-(pyrrolidin-1-yl)ethan-1-one. The titled active agent can potentially serve as a powerful synthetic opiate with an improved affinity and selectivity toward opioid receptors (ORs). This hypothesis was postulated based on docking studies regarding the respective complexes between the designed ligand and µ-OR, δ-OR, and κ-OR. The key step of the elaborated asymmetric synthesis of novel analog involves lipase-catalyzed kinetic resolution of racemic 1-(morpholin-4-yl)propan-2-ol, which was accomplished on a 10 g scale via an enantioselective transesterification employing vinyl acetate as an irreversible acyl donor in tert-butyl methyl ether (MTBE) as the co-solvent. Next, the obtained homochiral (S)-(+)-morpholino-alcohol (>99% ee) was functionalized into corresponding chloro-derivative using thionyl chloride (SOCl2) or the Appel reaction conditions. Further transformation with N-diphenylacetyl-1-pyrrolidine under phase-transfer catalysis (PTC) conditions using O2-saturated DMSO/NaOH mixture as an oxidant furnished the desired levorotatory isomer of the title product isolated in 26% total yield after three steps, and with 89% ee. The absolute configuration of the key-intermediate of (R)-(–)-iso-moramide was determined using a modified form of Mosher’s methodology. The preparation of the optically active dextrorotatory isomer of the titled product (87% ee) was carried out essentially by the same route, utilizing (R)-(–)-1-(morpholin-4-yl)propan-2-ol (98% ee) as a key intermediate. The spectroscopic characterization of the ethereal analog of iso-moramide and the enantioselective retention relationship of its enantiomers using HPLC on the cellulose-based chiral stationary phase were performed. Moreover, as a proof-of-principle, single-crystal X-ray diffraction (XRD) analysis of the synthesized 2-[(2R)-2-(morpholin-4-yl)propoxy]-2,2-diphenyl-1-(pyrrolidin-1-yl)ethan-1-one is reported.

Mesoporosity and Acidity Manipulation in ZSM‐23 and theirn‐Hexadecane Hydroisomerization Performance

AbstractThe enhanced mesoporosity in the networks is expected to offer a potential route to surmount mass‐transport constraints within one‐dimensional microporous structural zeolites. Highly crystalized ZSM‐23 zeolite was synthesized and subsequently post‐treated with alkali‐etching and acid‐etching, the effects of post‐treatments on the physical and chemical properties of the parent zeolite were investigated via XRD, N2physical adsorption, FE‐SEM, TEM,27Al MAS NMR, Py‐IR and NH3‐TPD. The catalytic activity of various Pt supported bifunctional catalysts was investigated vian‐hexadecane hydroisomerization. The post‐treated process not only increased the pore volume as well as the specific surface area, which efficiently improved the diffusion efficiency, but also changed the acidity and acid distribution of zeolite: alkali treatment could increase the content of total Brönsted acid while acid treatment exhibited an opposite trend. Acid treatment effectively promoted the density of weak Brönsted acid sites and suppressed the med‐strong Brönsted acid sites. With the manipulation of acidity and development of mesoporosity in zeolite, the formation of isomers and the suppression of cracked products in then‐hexadecane hydroisomerization were accomplished. The catalytic performance of catalysts showed that acid treatment could effectually promote the formation of isomeric products and inhibit cracking reactions. Especially, Pt/Z(1.0 HN) catalyst with suitable distribution of acid sites and textural properties, exhibited an outstandingn‐C16hydroisomerization performance with the highesti‐C16yield of 64 wt.% at 340 °C.

Production of diverse brGDGTs by Acidobacterium Solibacter usitatus in response to temperature, pH, and O2 provides a culturing perspective on brGDGT proxies and biosynthesis.

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are bacterial membrane lipids that are frequently employed as paleoenvironmental proxies because of the strong empirical correlations between their relative abundances and environmental temperature and pH. Despite the ubiquity of brGDGTs in modern and paleoenvironments, the source organisms of these enigmatic compounds have remained elusive, requiring paleoenvironmental applications to rely solely on observed environmental correlations. Previous laboratory and environmental studies have suggested that the globally abundant bacterial phylum of the Acidobacteria may be an important brGDGT producer in nature. Here, we report on experiments with a cultured Acidobacterium, Solibacter usitatus, that makes a large portion of its cellular membrane (24 ± 9% across all experiments) out of a structurally diverse set of tetraethers including the common brGDGTs Ia, IIa, IIIa, Ib, and IIb. Solibacter usitatus was grown across a range of conditions including temperatures from 15 to 30°C, pH from 5.0 to 6.5, and O2 from 1% to 21%, and demonstrated pronounced shifts in the degree of brGDGT methylation across these growth conditions. The temperature response in culture was in close agreement with trends observed in published environmental datasets, supporting a physiological basis for the empirical relationship between brGDGT methylation number and temperature. However, brGDGT methylation at lower temperatures (15 and 20°C) was modulated by culture pH with higher pH systematically increasing the degree of methylation. In contrast, pH had little effect on brGDGT cyclization, supporting the hypothesis that changes in bacterial community composition may underlie the link between cyclization number and pH observed in environmental samples. Oxygen concentration likewise affected brGDGT methylation highlighting the potential for this environmental parameter to impact paleotemperature reconstruction. Low O2 culture conditions further resulted in the production of uncommon brGDGT isomers that could be indicators of O2 limitation. Finally, the production of brGTGTs (trialkyl tetraethers) in addition to the previously discovered iso-C15-based mono- and diethers in S. usitatus suggests a potential biosynthetic pathway for brGDGTs that uses homologs of the archaeal tetraether synthase (Tes) enzyme for tetraether synthesis from diethers.

Two-Step, One-Pot Pyrrole Synthesis by Iron-Catalyzed ­Carboamination/Copper-Mediated Cyclization

AbstractHerein we report a method for pyrrole synthesis via iron-catalyzed carboamination/copper-mediated cyclization that is completely regioselective for the formation of 1,2,4-trisubstituted products. This two-step, one-pot process offers significant improvements to previously reported conditions including the use of a readily available copper(I) source and a markedly less arduous experimental procedure. Exploration of the substrate scope reveals a variety of arylacetylenes undergo pyrrole formation to afford single isomer products. Isotopic labelling data points to a mechanism involving activation of the alkyne moiety by the copper(I) reagent during the cyclization step.

Ni-Loaded 2D Zeolitic Imidazolate Framework as a Heterogeneous Catalyst with Highly Activity for Ethylene Dimerization

Metal–organic frameworks (MOFs) hold great potential in heterogeneous catalysis due to their unique properties and tunable structures. Zeolitic imidazolate frameworks (ZIFs) are series of classical MOFs that have been widely studied, where Zn2+ is coordinated with four imidazoles to form a tetrahedral structure. ZIF-L, one type of ZIF, is known for its unique two-dimensional (2D) leaf-like morphology and large external specific surface area. In this work, we reported a facile and green synthesis of the Ni-loaded ZIF-L (Ni-ZIF-L) catalysts, where water as solvent and product collection by filtration make the preparation easy for large-scale industrial production. Considering the incompatibility of the d8 electron configuration of Ni with the three-dimensional (3D) framework of ZIF-L, Ni can only be selectively anchored to the surface of ZIF-L. The Ni-ZIF-L has shown high crystallinity and 2D leaf-like microflakes similar to those of pure ZIF-L. After systematic analysis, we speculate that the Ni sites in Ni-ZIF-L samples have a square planar configuration, which should be coordinated by two imidazole groups from the framework, one NO3– group, and one free imidazole group. Ni-ZIF-L possesses fully exposed Ni active sites and a large specific surface area, accounting for the good performance for ethylene dimerization. In addition, the large particle size of the Ni-ZIF-L catalyst is beneficial for separation. With the assistance of cocatalyst, Ni-ZIF-L achieves an average ethylene turnover frequency of 330 320 moles of ethylene per mole of Ni per hour (1-butene selectivity >90%)) under 40 °C and 30 bar, comparable to the activity of the benchmark heterogeneous catalyst. The isotope experiments are used to illustrate that the ethylene dimerization catalyzed by Ni-ZIF-L follows the Cossee-Arlman mechanism, which also rationalizes the high catalytic activity and the small amount of isomerization and trimerization product formation.

ETHOXYCARBONYLATION OF PENTENE-1 IN THE PRESENCE OF PdCl2(PPh3)2-PPh3-AlCl3SYSTEM

Reactions based on CO allow the synthesis of almost all oxygen-containing organic compounds, which are important raw materials for obtaining practically valuable products of wide consumption. Alkoxycarbonylation of olefins with CO and various alcohols in the presence of metal complex catalysts synthesizes esters of carboxylic acids in one step. The purpose:In accordance with previously synthesized ethyl esters of enanthic and 2-methylcapronic acids in the reaction of ethoxycarbonylation of hexene-1 with СОin the presence of the catalytic system PdCl2(PPh3)2-PPh3-AlCl3in this work we planned to synthesize ethyl esters of capronic and 2-methylvalerian acids by hydroethoxycarbonylation of pentene-1 with CO in the presence of the same catalytic system. Methodology: The autoclave was sealedand then filled with CO to 1.5 MPa pressure. The pressure of CO was brought to 2.0 MPa, the temperature was raised to 1000C for 1 hour and at this pressure and temperature the reaction mixture was stirred for 5 h. Results and discussion: Experimental results show that the reaction proceeds with the formation of two isomeric products of linear (EECA) and branched structure (EE-2-MVA). Optimal reaction conditions have been found, at which the yield of the target products (sum of isomeric esters of EECA and EE-2-MVA) reaches 74.72 %. Conclusion:The catalytic activity of the three-component system PdCl2(PPh3)2-PPh3-AlCl3 containing AlCl3as a promoter in the reaction of ethoxycarbonylation of pentene-1 has been established. The reaction proceeds with the formation of two isomeric products of linear (EECA) and branched structure (EE-2-MVA).

Solvent free selective acylation of phenol by HF–modified saponite catalysts

The preparation and characterization of hydrofluoric acid (HF)–modified saponite catalysts and their application in the selective synthesis of 4–hydroxyacetophenone through acylation reaction is reported. This method is solvent–free and would be effectively scaled up for the selective preparation of the para–isomer product. The prepared 4–hydroxyacetophenone was characterized by 1H and 13C NMR, FT–IR, and UV–Visible spectroscopic techniques. The experimental conditions were milder than in conventional methods and gave excellent yields using low amounts of acid–treated catalysts, which were found to be superior to other catalysts for this particular reaction. The catalysts were found to be environmentally benign, cost-effective, and recyclable over three cycles without appreciable loss in activity. The reaction seemed to be controlled by the Lewis acidity and the porosity of treated saponite, and thus this work opens a new strategy for the use of clay minerals as catalysts in Fine Chemistry reactions.

The N(2D) + CH2CHCN (Vinyl Cyanide) Reaction: A Combined Crossed Molecular Beam and Theoretical Study and Implications for the Atmosphere of Titan.

The reaction of electronically excited nitrogen atoms, N(2D), with vinyl cyanide, CH2CHCN, has been investigated under single-collision conditions by the crossed molecular beam (CMB) scattering method with mass spectrometric detection and time-of-flight (TOF) analysis at the collision energy, Ec, of 31.4 kJ/mol. Synergistic electronic structure calculations of the doublet potential energy surface (PES) have been performed to assist in the interpretation of the experimental results and characterize the overall reaction micromechanism. Statistical (Rice–Ramsperger–Kassel–Marcus, RRKM) calculations of product branching fractions (BFs) on the theoretical PES have been carried out at different values of temperature, including the one corresponding to the temperature (175 K) of Titan’s stratosphere and at a total energy corresponding to the Ec of the CMB experiment. According to our theoretical calculations, the reaction is found to proceed via barrierless addition of N(2D) to the carbon–carbon double bond of CH2=CH–CN, followed by the formation of cyclic and linear intermediates that can undergo H, CN, and HCN elimination. In competition, the N(2D) addition to the CN group is also possible via a submerged barrier, leading ultimately to N2 + C3H3 formation, the most exothermic of all possible channels. Product angular and TOF distributions have been recorded for the H-displacement channels leading to the formation of a variety of possible C3H2N2 isomeric products. Experimentally, no evidence of CN, HCN, and N2 forming channels was observed. These findings were corroborated by the theory, which predicts a variety of competing product channels, following N(2D) addition to the double bond, with the main ones, at Ec = 31.4 kJ/mol, being six isomeric H forming channels: c-CH(N)CHCN + H (BF = 35.0%), c-CHNCHCN + H (BF = 28.1%), CH2NCCN + H (BF = 26.3%), c-CH2(N)CCN(cyano-azirine) + H (BF = 7.4%), trans-HNCCHCN + H (BF = 1.6%), and cis-HNCCHCN + H (BF = 1.3%), while C–C bond breaking channels leading to c-CH2(N)CH(2H-azirine) + CN and c-CH2(N)C + HCN are predicted to be negligible (0.02% and 0.2%, respectively). The highly exothermic N2 + CH2CCH (propargyl) channel is also predicted to be negligible because of the very high isomerization barrier from the initial addition intermediate to the precursor intermediate able to lead to products. The predicted product BFs are found to have, in general, a very weak energy dependence. The above cyclic and linear products containing an additional C–N bond could be potential precursors of more complex, N-rich organic molecules that contribute to the formation of the aerosols on Titan’s upper atmosphere. Overall, the results are expected to have a significant impact on the gas-phase chemistry of Titan’s atmosphere and should be properly included in the photochemical models.

Cyclic ADP ribose isomers: Production, chemical structures, and immune signaling.

Cyclic adenosine diphosphate (ADP)-ribose (cADPR) isomers are signaling molecules produced by bacterial and plant Toll/interleukin-1 receptor (TIR) domains via nicotinamide adenine dinucleotide (oxidized form) (NAD+) hydrolysis. We show that v-cADPR (2'cADPR) and v2-cADPR (3'cADPR) isomers are cyclized by O-glycosidic bond formation between the ribose moieties in ADPR. Structures of 2'cADPR-producing TIR domains reveal conformational changes that lead to an active assembly that resembles those of Toll-like receptor adaptor TIR domains. Mutagenesis reveals a conserved tryptophan that is essential for cyclization. We show that 3'cADPR is an activator of ThsA effector proteins from the bacterial antiphage defense system termed Thoeris and a suppressor of plant immunity when produced by the effector HopAM1. Collectively, our results reveal the molecular basis of cADPR isomer production and establish 3'cADPR in bacteria as an antiviral and plant immunity-suppressing signaling molecule.