Propenyl Ether Research Articles

Use of stability statistics in the selection of Clausena heptaphylla (Roxb.) Wight & Arn for novel anethole rich strain (Jor Lab CH-2).

Anethole is an industrially important compound which is extensively used in pharmaceuticals, cosmetics, perfumery, food and confectioneries. Anethole is primarily obtained from fennel, anise, and star anise which is highly expensive. Therefore, a study was performed to identify a cost-effective and natural anethole rich strain of Clausena heptaphylla through selection and confirmed through multilocation trial. The study was conducted using 23 accessions collected from North eastern region of India from 2014-2018 (initial evaluation trial) and 2018-2022 (multilocation trial). The initial trial was conducted in the experimental farm of CSIR-NEIST, Jorhat, Assam using Complete Randomized Block Design with three replications. Five agronomical traits (plant height, leaf length, leaf width, number of stem branching, herbage yield per plant per cutting) along with essential oil yield and anethole content were evaluated which led to the identification of anethole rich strain of C. heptaphylla. This identified strain was further evaluated along with the two check genotypes for stability based on three yield parameters viz. herbage yield, essential oil yield and anethole content at four multi-locations (Imphal, Jorhat, Runne and Madang) for four years using the same experimental design. The identified superior line (Jor Lab CH-2) showed consistent performance for the studied yield parameters across all the environments maintaining its superiority. The identified strain exhibited average herbage yield of 1.2 Kg/plant/cutting and essential oil yield of 1.22%. The GC-MS analysis of the essential oil depicted trans anethole as the major constituent (93.25%) followed by estragole (4.85%) while benzene, 1,2-dimethoxy-4-(1-propenyl Isoeugenol methyl ether and cis-anethole were the trace components. This is the first novel report of anethole rich variant of C. heptaphylla which has undergone multilocational trial over the years. Jor Lab CH-2 strain will open a new scope for the industries to isolate anethole from a different source in a cost-effective approach.

Metal–Organic-Framework-Derived Copper Catalysts for the Hydrogenolysis of Lignin into Monomeric Phenols

Reductive catalytic fractionation (RCF) of lignocellulosic biomass has emerged as a leading biorefinery strategy. Herein, we present a copper-based catalyst (CuO/C) derived from a metal–organic backbone (HKUST-1) with enhanced catalytic performance for RCF of woody sawdust, which affords high yields of propyl and propanol end-chain monomeric phenols (15.5 wt % in softwoods and 46.7 wt % in hardwoods) via the C–O bond scission. A series of conifer β-O-4 models and their deuterated analogues revealed that the synergistic action of CuO/C and hydrogen could effectively cleave aryl ether linkages. It was deduced that lignin alcoholysis led to partial α-OH etherification of the β-O-4′ units, which promoted the C–O bond breakage of Cα-OMe and Cβ-O, thus giving propanol phenolic compounds through the hydrogenation of coniferyl alcohol over the CuO/C catalyst. When both α- and γ-OH of β-O-4′ motifs were meoxylated, the para-propyl phenolics were obtained through the scission of C–O linkages (Cα-OMe and Cβ-O), followed by the Cγ-OMe cleavage of propenyl ethers and hydrogenation of propenyl phenols. We envision that this work may pave the way for the development of non-noble catalysts with high reactivity and selectively for lignin valorization.

Site-specific scaling relations observed during methanol-to-olefin conversion over ZSM-5 catalysts

The conversion of methanol over ZSM-5 catalysts was studied using step response and temperature-programmed desorption and surface reaction analyses in a temporal analysis of products reactor, as well as quasi-elastic neutron scattering and Fourier transform infrared investigations, buttressed by archived 13C magic angle spinning nuclear magnetic resonance studies. The results were combined with micro-kinetic models that simulated the formation of the first C–C bond and primary olefin(s) from methanol. Dimethyl ether was the major surface oxygenate and a source of surface methoxy species. Propylene, the major olefin produced from dimethyl ether, was formed with a reaction barrier of ∼ 200 kJ mol−1, in agreement with archived density functional theory calculations. Propylene could form from dimethyl ether via a methoxymethyl mechanism under intrinsic kinetic conditions. Site-specific scaling relations between the barriers to methyl propenyl ether and methoxy methyl species formation and dimethyl ether desorption were observed. The active sites of the ZSM-5 catalysts can be locally optimised and selectively tuned to improve their activity during the conversion of methanol to olefin(s).

Optimization of the reaction conditions for the synthesis of 2,3,5-trimethylpyridine from 3-amino-2-methylpropenal and methylethylketone

The influence of temperature, reaction time, and type of the catalyst on the yield of the 2,3,5-trimethylpyridine (collidine) from 3-amino-2-methylpropenal and methylethylketone was investigated. 3-Amino-2-methylpropenal was synthesized from 3-ethoxy-2-methylacrolein previously synthesized from methylmalondialdehyde tetraethyl acetal, obtained from triethyl orthoformate and propenyl ether. The optimal conditions for the investigated synthesis were temperature of 150 ?C, reaction time 24 h, and the CH3COOH/pTsOH catalyst. This synthesis is the first successful attempt to synthesize 2,3,5-trimethylpyridine in an acid medium.

Mechanistic insights into the conversion of dimethyl ether over ZSM-5 catalysts: A combined temperature-programmed surface reaction and microkinetic modelling study

The rates of adsorption, desorption, and surface reaction of dimethyl ether (DME) to olefins over fresh and working ZSM-5 catalysts with different Si/Al ratios (36 and 135) were decoupled using a combination of temperature-programmed surface reaction experiments and microkinetic modelling. Transient reactor performance was simulated by solving coupled 1D nonlinear partial differential equations accounting for elementary steps during the induction period based on the methoxymethyl mechanism on the zeolite catalyst and axial dispersion and convection in the reactor. Propylene is the major olefin formed, and site-specific scaling relations between the activation energies of DME desorption and barriers to the formation of methoxymethyl and methyl propenyl ether are observed. Six ensembles of sites are observed with a maximum of three adsorption/desorption sites and three adsorption/desorption/reaction sites. Barriers are generally higher for working catalysts than fresh catalysts. Activation energies of propylene formation of ca. 200 kJ mol−1 are obtained, corroborating direct mechanistic proposals.

Highly Productive Synthesis of 1-Propenyloxybutan-1-ol Under Solvent-Free Homogeneous Ruthenium Catalyst Conditions

The 1-propenyl ethers bearing free hydroxyl groups of CH3CH=CH–O–A–OH type (hydroxyalkyl 1-propenyl ethers, 1-propenyloxyalcohols) are the most desired as the reactive diluents for photopolymerizable systems with enhanced reactivity or intermediates for the synthesis of hybrid monomers for special applications. The ruthenium complexes-catalyzed isomerization of allyl ethers under solvent-free conditions is an atom-economical and environmentally sustainable method for their production. Here, the reaction conditions and limitations for the highly productive and selective synthesis of model 4-(1-propenyloxy)butan-1-ol have been investigated. The minimal loading of ruthenium pre-catalysts needed for completion of reaction within reasonable times was priority assumption. It was found that [RuClH(CO)(PPh3)3] or [RuCl2(PPh3)3] exhibited extremely high catalytic activity under optimized non-oxidative reaction conditions. The key effect of reaction temperature on the activation pre-catalyst and the exothermal effects of isomerization was discovered. The practically quantitative yields of 4-(1-propenyloxy)butan-1-ol were achieved with using of very low loading of [Ru] (5 ppm) and Bu3N (to maintain reaction chemoselectivity) at the temperature of 120 °C for only 0.5 h. Consequently, the attained TON (turnover number) and TOF (turnover frequency) values of ca. 198,000 and 390,000 h−1 were unprecedentedly high and industrial attractive. On the other hand, the direct recycling of ruthenium catalyst is not a reasonable method for improving catalyst productivity.

Synthesis of 15 N-labelled 3,5-dimethylpyridine.

15N‐labelled pyridines are liquid‐ and solid‐state nuclear magnetic resonance (NMR) probes for chemical and biological environments because their 15N chemical shifts are sensitive to hydrogen‐bond and protonation states. By variation of the type and number of substituents, different target pyridines can be synthesized exhibiting different pK a values and molecular volumes. Various synthetic routes have been described in the literature, starting from different precursors or modification of other 15N‐labelled pyridines. In this work, we have explored the synthesis of 15N 15N‐labelled pyridines using a two‐step process via the synthesis of alkoxy‐3,4‐dihydro‐2H‐pyran as precursor exhibiting already the desired pyridine substitution pattern. As an example, we have synthesized 3,5‐dimethylpyridine‐15N (lutidine‐15N) as demonstrated by 15N‐NMR spectroscopy. That synthesis starts from methacrolein, propenyl ether, and 15N‐labelled NH4Cl as nitrogen source.

Transient kinetic studies and microkinetic modeling of primary olefin formation from dimethyl ether over ZSM‐5 catalysts

AbstractThe formation of primary olefins from dimethyl ether (DME) was studied over ZSM‐5 catalysts at 300°C using a novel step response methodology in a temporal analysis of products (TAP) reactor. For the first time, the TAP reactor framework was used to conduct single‐ and multiple‐step response cycles of DME (balance argon) over a shallow bed with the continuous flow panel. Propylene is the major primary olefin and portrays an S‐shaped profile with a preceding induction period when it is not observed in the gas phase. Methanol and water portray overshoot profiles due to their different rates of generation and consumption. DME effluent shows a rapid rise halfway to its steady‐state value leading to a slow rise thereafter because of its high desorption rates followed by subsequent reactions involving DME in further steps during the induction period. To analyze the experimental data quantitatively, nine reaction schemes were compared, and kinetic parameters were obtained by solving a transient plug flow reactor model with coupled dispersion, convection, adsorption, desorption, and reaction steps. The methoxymethyl pathway involving dimethoxyethane and methyl propenyl ether gives the closest match to experimental data in agreement with recent density functional theory studies. Gaseous dispersion coefficients of ca. 10−9 m2 s−1 were obtained in the TAP reactor. The novel experimental data validated against the transient kinetic model suggests that after the formation of initial species, the bottleneck in propylene formation is the transformation of the initial C–C bond, that is dimethoxyethane formed initially from DME and methoxymethyl groups. DME adsorption on ZSM‐5 catalyst generates surface methoxy groups, which further react with the feed to give methoxymethyl groups. These methoxymethyl groups are regenerated through a series of reactions involving intermediates such as dimethoxymethane and methyl propenyl ether before propylene formation.

Bidirectional metal‐free ROMP from difunctional organic initiators

Bidirectional metal‐free ROMP from difunctional organic initiators

Effect of Side-Chain Carbonyl Groups on the Interface of Vinyl Polymers with Water

The nature of the polymer-water interface in the poly(methyl 2-propenyl ether) (PMPE)-water model system is investigated by sum-frequency generation spectroscopy, which at the moment gives the best depth resolution among available techniques. PMPE, synthesized via living cationic polymerization, is structurally similar to poly(methyl methacrylate) (PMMA) except for lacking a carbonyl group. We here probe the polymer local conformation as well as the aggregation states of water at the interface. Comparing the results of our measurements to the PMMA-water system, the effect of a carbonyl group on the water structure at the interface is discussed. This knowledge should be crucial to the design and construction of highly functionalized polymer interfaces for bioapplications.

Analysis of Potential Energy Surface for Butanone Isomerization

The potential energy surfaces for butanone isomerization have been investigated by density function theory calculation. Six main reaction pathways are confirmed using the intrinsic reaction coordinate method, and the corresponding isomerization products are 1-buten-2-ol, 2-buten-2-ol, butanal or 1-buten-1-ol, methyl 1-propenyl ether, methyl allyl ether, and ethyl vinyl ether, respectively. Among them, there are three pathways through butylene oxide, indicating butylene oxide is an important intermediate product during butanone isomerization. The calculated vertical ionization energies of the reactant and its products are in a good agreement with the experimental values available. From the consideration for the relative energies of transition states and the number of high-energy barriers we infer that the reaction pathway butanone→1-buten-2-ol →2-buten-2-ol is the most competitive. The obtained results are informative for future studies on isomerization of ketone molecules.

Advances in cationic photopolymerization

This review discusses cationic UV-curing processes of vinyl ethers, propenyl ethers, and epoxy monomers. Cationic photopolymerization based on photogeneration of acid from onium salts induced by UV light and consecutive polymerization initiated by photogenerated acid was first proposed at the end of the 1970s. The process engendered high interest both in academia and in industry. Cationic photoinduction presents some advantages over comparable radical-mediated processes, particularly the absence of inhibition by oxygen, low shrinkage, and good adhesion, and mechanical properties of the UV-cured materials. Moreover, the monomers employed are generally less toxic and irritant than acrylates and methacrylates, which are widely used in radical photopolymerization. In this overview, particular emphasis is given to our recent contributions to the field of cationic photopolymerization for different classes of monomers.

Efficient syntheses of C20-carotene and crocetin (descrocetin) esters promoted by an acidic ionic liquid

Efficient syntheses of C20-carotene and crocetin or descrocetin esters from fumaraldehyde bis-dimethylacetal are described. The key steps of these syntheses are the reactions of fumaraldehyde and (2E,4E,6E)-octa-2,4,6-trienedial bis-dimethylacetals with alkyl vinyl or alkyl propenyl ethers promoted by the acidic ionic liquid, [emim][HSO4].

1,2‐Bis(trifluoromethyl)ethene‐1,2‐dicarbonitrile: Enol Ethers and Ketene Acetals as Cycloaddition Partners

Abstract(E)‐ and (Z)‐1,2‐bis(trifluoromethyl)ethene‐1,2‐dicarbonitrile ((E)‐ and (Z)‐BTE, resp., =(E)‐ and (Z)‐2,3‐bis(trifluoromethyl)but‐2‐enedinitrile) were used as a stereochemical probe in studying (2+2) cycloadditions of acceptor with donor alkenes. The additions to methyl (E)‐ and (Z)‐propenyl ether gave rise to the eight conceivable cyclobutanes 8, although in different ratios in reactions of (E)‐ and (Z)‐BTE. The 19F‐NMR data served the structural assignment and the quantitative analysis. The mechanistic discussion is based on rotations and ring closures of the assumed 1,4‐zwitterionic intermediates. Dimethylketene dimethyl acetal, methylketene dimethyl acetal, and ketene diethyl acetal show an increasing rate in their reactions with BTE as well as in the equilibration of the cycloadducts.

Ruthenium(IV)‐Catalyzed Isomerization of the CC Bond of O‐Allylic Substrates: A Theoretical and Experimental Study

A general mechanism to rationalize Ru(IV) -catalyzed isomerization of the C=C bond in O-allylic substrates is proposed. Calculations supporting the proposed mechanism were performed at the MPWB1K/6-311+G(d,p)+SDD level of theory. All experimental observations in different solvents (water and THF) and under different pH conditions (neutral and basic) can be interpreted in terms of the new mechanism. Theoretical analysis of the transformation from precatalyst to catalyst led to structural identification of the active species in different media. The experimentally observed induction period is related to the magnitudes of the energy barriers computed for that process. The theoretical energy profile for the catalytic cycle requires application of relatively high temperatures, as is experimentally observed. Participation of a water molecule in the reaction coordinate is mechanistically essential when the reaction is carried out in aqueous medium. The new mechanistic proposal helped to develop a new experimental procedure for isomerization of allyl ethers to 1-propenyl ethers under neutral aqueous conditions. This process is an unique example of efficient and selective catalytic isomerization of allyl ethers in aqueous medium.

ChemInform Abstract: Isomerization of Allyl Ethers Initiated by Lithium Diisopropylamide.

AbstractA wide range of allylic ethers is converted to the corresponding (Z)‐propenyl ethers on treatment with LDA.

Isomerization of Allyl Ethers Initiated by Lithium Diisopropylamide

Lithium diisopropylamide (LDA) promotes virtually quantitative conversion of allylic ethers to (Z)-propenyl ethers. It was discovered that allylic ethers can be isomerized efficiently with very high stereoselectivity to (Z)-propenyl ethers by LDA in THF at room temperature. The reaction time for the conversion increases with more sterically hindered allylic ethers. Different amides were also compared with LDA for their ability to effect this isomerization.

ChemInform Abstract: The Electron-Deficient Olefin 2,2-Bis(trifluoromethyl)ethylene-1,1- dicarbonitrile: Hydride Abstractions from Allyl and Isobutenyl Ethers and Thioethers.

The title compound (BTF) combines with isobutenyl and methallyl ethers and thioethers furnishing the same formal insertion products 5; an ion pair arising from hydride transfer is proposed as a common intermediate. Allyl ethers (and thioethers) are subject to the same reaction whereas the isomeric propenyl ethers undergo [2+2] cycloaddition with BTF. The rate constant for the reaction of ethyl methallyl ether and BTF shows only a modest dependence on solvent polarity

ChemInform Abstract: Isomerization of Allyl Ethers of Diols and Triols Catalyzed by Ruthenium Complexes.

The allyl and propenyl ethers of diols and polyols have recently attracted increasing attention as monomers and comonomers [1–2]. Most convenient method of the preparation of propenyl ethers consists in isomerization of the corresponding, readily available allyl ethers. Moreover, this isomerization is a key step of deprotection of hydroxyl group, protected as allyl ether [3,4]. Particularly convenient catalysts of the isomerization of allyl to propenyl ethers are transition metal complexes. Complexes of ruthenium [5–8], rhodium [3,4], iridium [9], palladium [10], chromium [11], molybdenum [12], iron [13], platinum [14] and cobalt [15] were applied. In this communication, we describe the synthesis of propenyl ethers via isomerization of the corresponding allyl ethers of diols and triols catalyzed by [RuClH(CO)(PPh3)3] (Table). Other investigated ruthenium and rhodium complexes ([RuCl2(PPh3) 3], [ RuH 2(PPh3) 4], [ Ru(CO) 3(PPh3) 2], [ RhH(CO)(PPh 3) 3], [RuCl33H2O], [RhCl33H2O]) were less effective or even completely inactive. Quantitative yields of propenyl ethers were obtained only if a substrate contained neither triple bond nor allyl-hydroxyl group. Allyl ethers of 2-butyne-1,4-diol did not undergo isomerization to the corresponding propenyl ethers. It is likely that in this case stable acetylene complexes are formed:

Oligomer formation during gas-phase ozonolysis of small alkenes and enol ethers: new evidence for the central role of the Criegee Intermediate as oligomer chain unit

Abstract. An important fraction of secondary organic aerosol (SOA) formed by atmospheric oxidation of diverse volatile organic compounds (VOC) has recently been shown to consist of high-molecular weight oligomeric species. In our previous study (Sadezky et al., 2006), we reported the identification and characterization of oligomers as main constituents of SOA from gas-phase ozonolysis of small enol ethers. These oligomers contained repeated chain units of the same chemical composition as the main Criegee Intermediates (CI) formed during the ozonolysis reaction, which were CH2O2 (mass 46) for alkyl vinyl ethers (AVE) and C2H4O2 (mass 60) for ethyl propenyl ether (EPE). In the present work, we extend our previous study to another enol ether (ethyl butenyl ether EBE) and a variety of structurally related small alkenes (trans-3-hexene, trans-4-octene and 2,3-dimethyl-2-butene). Experiments have been carried out in a 570 l spherical glass reactor at atmospheric conditions in the absence of seed aerosol. SOA formation was measured by a scanning mobility particle sizer (SMPS). SOA filter samples were collected and chemically characterized off-line by ESI(+)/TOF MS and ESI(+)/TOF MS/MS, and elemental compositions were determined by ESI(+)/FTICR MS and ESI(+)/FTICR MS/MS. The results for all investigated unsaturated compounds are in excellent agreement with the observations of our previous study. Analysis of the collected SOA filter samples reveal the presence of oligomeric compounds in the mass range 200 to 800 u as major constituents. The repeated chain units of these oligomers are shown to systematically have the same chemical composition as the respective main Criegee Intermediate (CI) formed during ozonolysis of the unsaturated compounds, which is C3H6O2 (mass 74) for ethyl butenyl ether (EBE), trans-3-hexene, and 2,3-dimethyl-2-butene, and C4H8O2 (mass 88) for \\textit{trans}-4-octene. Analogous fragmentation pathways among the oligomers formed by gas-phase ozonolysis of the different alkenes and enol ethers in our present and previous study, characterized by successive losses of the respective CI-like chain unit as a neutral fragment, indicate a similar principal structure. In this work, we confirm the basic structure of a linear oligoperoxide – [CH(R)-O-O]n – for all detected oligomers, with the repeated chain unit CH(R)OO corresponding to the respective major CI. The elemental compositions of parent ions, fragment ions and fragmented neutrals determined by accurate mass measurements with the FTICR technique allow us to assign a complete structure to the oligomer molecules. We suggest that the formation of the oligoperoxidic chain units occurs through a new gas-phase reaction mechanism observed for the first time in our present work, which involves the addition of stabilized CI to organic peroxy radicals. Furthermore, copolymerization of CI simultaneously formed in the gas phase from two different unsaturated compounds is shown to occur during the ozonolysis of a mixture of \\textit{trans}-3-hexene and ethyl vinyl ether (EVE), leading to formation of oligomers with mixed chain units C3H6O2 (mass 74) and CH2O2 (mass 46). We therefore suggest oligoperoxide formation by repeated peroxy radical-stabilized CI addition to be a general reaction pathway of small stabilized CI in the gas phase, which represents an alternative way to high-molecular products and thus contributes to SOA formation.