Methyl Sorbate Research Articles

Synthesis of Methyl Sorbate Catalyzed by Deep Eutectic Solvent Based on Choline Chloride: Kinetics and Optimization

Synthesis of Methyl Sorbate Catalyzed by Deep Eutectic Solvent Based on Choline Chloride: Kinetics and Optimization

Boron-Based Lewis Pairs Catalyzed Living, Regioselective, and Topology-Controlled Polymerization of (E, E)-Alkyl Sorbates.

It remains as a great challenge to realize living and controlled polymerization of renewable monomers by the boron-based Lewis pairs. Here, strong nucleophilic N-heterocyclic olefins (NHOs) or N-heterocyclic carbenes (NHCs) as Lewis bases, and boron-based compounds as Lewis acids, are employed to construct LPs for polymerization of alkyl sorbates, including (E, E)-methyl sorbate and (E, E)-ethyl sorbate. Systematic investigation reveals that the combinations of B(C6 F5 )3 with appropriate acidity and steric hindrance, and strong nucleophilic NHOs promote living and controlled polymerization of alkyl sorbates in 100% 1,4-addition manner, furnishing polymers with predicted molecular weight (Mw up to 56.6kgmol-1 ) and narrow molecular weight distribution (Đ as low as 1.12). Furthermore, topology analysis shows that NHC1/B(C6 F5 )3 LP produce PMS possessing cyclic structure.

Lewis Pair Catalyzed Regioselective Polymerization of (E,E)-Alkyl Sorbates for the Synthesis of (AB)n Sequenced Polymers.

In this contribution, Lewis pairs (LPs) composed of N-heterocyclic olefins (NHOs) with different steric hindrance and nucleophilicity as Lewis bases (LBs) and Al-based compounds with comparable acidity but different steric hindrance as Lewis acids (LAs) were applied for 1,4-selective polymerization of (E,E)-methyl sorbate (MS) and (E,E)-ethyl sorbate (ES). The effects of steric hindrance, electron-donating ability, and acidity of LPs on MS and ES polymerization were systematically investigated. High catalytic activity and high initiation efficiency can be achieved, leading to the formation of PMS with 100 % 1,4-selectivity, tunable molecular weight (Mw up to 333 kg mol-1 ), and narrow molecular weight distribution (MWD). Block copolymerization of ES and methyl methacrylate (MMA) was also realized. Meanwhile, this system can be applied to other homologous conjugated diene substrates. Furthermore, simple chemical reactions can efficiently convert PMS to different polymers with strict (AB)n sequence structures, such as poly(sorbic acid), poly(propylene-alt-methyl acrylate), poly(propylene-alt-acrylic acid), poly(propylene-alt-allyl alcohol), and poly(ethylene-alt-2-butylene).

Lewis Pair Catalyzed Regioselective Polymerization of (E,E)‐Alkyl Sorbates for the Synthesis of (AB)n Sequenced Polymers

AbstractIn this contribution, Lewis pairs (LPs) composed of N‐heterocyclic olefins (NHOs) with different steric hindrance and nucleophilicity as Lewis bases (LBs) and Al‐based compounds with comparable acidity but different steric hindrance as Lewis acids (LAs) were applied for 1,4‐selective polymerization of (E,E)‐methyl sorbate (MS) and (E,E)‐ethyl sorbate (ES). The effects of steric hindrance, electron‐donating ability, and acidity of LPs on MS and ES polymerization were systematically investigated. High catalytic activity and high initiation efficiency can be achieved, leading to the formation of PMS with 100 % 1,4‐selectivity, tunable molecular weight (Mw up to 333 kg mol−1), and narrow molecular weight distribution (MWD). Block copolymerization of ES and methyl methacrylate (MMA) was also realized. Meanwhile, this system can be applied to other homologous conjugated diene substrates. Furthermore, simple chemical reactions can efficiently convert PMS to different polymers with strict (AB)n sequence structures, such as poly(sorbic acid), poly(propylene‐alt‐methyl acrylate), poly(propylene‐alt‐acrylic acid), poly(propylene‐alt‐allyl alcohol), and poly(ethylene‐alt‐2‐butylene).

Spicing up olefin cross metathesis with the renewables estragole and methyl sorbate

Diene moieties conjugated to a carbonyl group are ubiquitous in nature and are present in compounds with relevant biological properties. Herein we investigate the cross metathesis (CM) of the renewable cross partners estragole and methyl sorbate (MeSo) to produce methyl 6-(4-methoxyphenyl)hexa-2,4-dienoate. By the judicious choice of the ruthenium-based metathesis catalysts, as well as the reaction conditions, it was possible to obtain good conversion and selectivity for the desired product in catalyst loadings as low as 50 ppm (0.005 mol%), with a minimal amount of solvent.

Direct observation of the formation of a cyclic poly(alkyl sorbate) via chain‐growth polymerization by an N‐heterocyclic carbene initiator and ring‐closing without extreme dilution

Abstract1,3‐Di‐tert‐butylimidazol‐2‐ylidene (NHCtBu), which is one of the typical N‐heterocyclic carbene (NHC), was found to initiate the anionic chain‐growth polymerization of methyl sorbate (MS) in toluene at −20°C. The polymerization was accelerated by an aluminum Lewis acid, that is, methylaluminum bis(2,6‐di‐tert‐butyl‐4‐methylphenoxide) (MAD), to afford cyclic poly(MS)s. Subsequently, thiol‐ene click reactions of poly(MS)s with two different alkanethiols were performed using a photoradical initiator to obtain graft‐like polymers, which was for the microscopic observation of the chains directly by transmittance electron microscope (TEM). The contamination of linear polymers was hardly observed. This means that the polymers synthesized by our synthetic strategy were indeed cyclic polymers. We also compared the theoretical and experimental chain diameter and width for the graft‐like cyclic polymers, where these values were dependent on the molecular weight of the cyclic polymers regulated by the feed monomer/initiator ratio and length of the alkanethiols, respectively.

Direct observation of cyclic poly(N-substituted maleimide)s with broad size distributions synthesized by anionic polymerization using an N-heterocyclic carbene and successive ring closure without high dilutions

The N-heterocyclic carbene 1,3-di-tert-butylimidazol-2-ylidene (NHCtBu) and its 1:1 adduct with methyl sorbate (MS) were found to initiate anionic polymerization of N-substituted maleimides (RMIs) in organic solvents at −20 °C to afford linear and cyclic poly(RMI)s, respectively. Quantitative monomer consumption was observed when a bulky aluminum Lewis acid, such as methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD), was used as an additive. In the presence of the NHCtBu:MS adduct as an initiator, monomer consumption was followed by ring closure without the need for highly diluted conditions to give cyclic poly(RMI)s containing α-terminal MS units, which exhibited an Mn of 3.4 × 103–6.2 × 103 and a broad polydispersity index (Mw/Mn = 2.43–2.65). Dilution was not required due to the presence of an α-terminal NHCtBu group, which acted as a counter cation for the propagating center during polymerization. The broad molecular weight distributions of the obtained polymers were ascribed to a chain transfer upon abstraction of the α-carbonyl proton of the RMIs, particularly to the neighboring NHCtBu cation unit. 1H NMR and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass analyses indicated that the proton transfer of the acidic proton was induced by the propagating anion. The topologies of the linear and cyclic poly(RMI)s were directly observed by transmission electron microscopy (TEM). Direct Observation of Cyclic Poly(N-substituted maleimide)s with Broad Size Distributions Synthesized by Anionic Polymerization using an N-Heterocyclic Carbene and Successive Ring Closure Without High Dilutions.

Direct Observation of a Cyclic Vinyl Polymer Prepared by Anionic Polymerization using N‐Heterocyclic Carbene and Subsequent Ring‐Closure without Highly Diluted Conditions

AbstractA 1:1 adduct of methyl sorbate (MS) and 1,3‐di‐tert‐butylimidazol‐2‐ylidene (NHCtBu) initiates anionic polymerization of a nonconjugated polar alkene, allyl methacrylate (AMA) in toluene at −20 °C. After the monomer is consumed quantitatively using a bulky aluminum Lewis acid, methylaluminum bis(2,6‐di‐tert‐butyl‐4‐methylphenoxide) (MAD), as an additive, successive ring‐closure occurs without highly dilute conditions to give a cyclic poly(AMA) containing α‐terminal MS unit, and an Mn of 8.8 × 103−58.5 × 103 with a narrow molecular dispersity index (Mw/Mn = 1.14–1.37). The lack of a need for dilution is due to the fact that an α‐terminal NHCtBu group is acting as the counter cation for the propagating center in the polymerization. From 1H NMR and matrix assisted laser desorption/ionization (MALDI‐TOF) mass spectra, combined with transmittance electron microscope (TEM) observation of a synthesized poly(AMA) with longer alkyl side chains prepared via a thiol‐ene click reaction, it is concluded that once the monomer is consumed, nucleophilic attack at the neighboring methine of the α‐terminal NHCtBu residue by the propagating anionic center causes ring‐closing to cyclic poly(AMA).

Synthesis of cyclic Poly(methyl methacrylate) via N-Heterocyclic carbene (NHC) initiated-anionic polymerization and subsequent ring-closing without need of highly dilute conditions

A cyclic polymethacrylate was prepared via the anionic polymerization of methyl methacrylate (MMA) initiated by a 1:1 adduct of methyl sorbate (MS) and a N-heterocyclic carbene (NHC) without the need for highly dilute conditions, because an α-terminal imidazolimium group is neighboring to the propagating anion during the polymerization. The polymerization proceeded quantitatively using methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD) as the Lewis acid to give the poly (MMA) with the MS unit in the α-terminus, and an Mn of 7.2 × 103–29.1 × 103 with a molecular weight distribution (Mw/Mn = 1.16-1.56). From proton (1H) NMR and matrix assisted laser desorption/ionization (MALDI-TOF) mass spectra, coupled with size exclusion chromatography (SEC) of the poly (MMA) produced before and after ozonolysis of the internal carbon-carbon double bond in the MS unit, we found that ring-closing reaction was induced by nucleophilic substitution of the propagating anion to the neighboring carbon of the α-terminal carbenyl (imidazolimium) group to synthesize cyclic poly (MMA) following complete the monomer consumption.

N-Heterocyclic Carbene Initiated Anionic Polymerization of (E,E)-Methyl Sorbate and Subsequent Ring-Closing to Cyclic Poly(alkyl sorbate).

A diene-based cyclic polymer has been synthesized by the anionic polymerization of methyl sorbate (MS) by an N-heterocyclic carbene (NHC) in the presence of a bulky aluminum Lewis acid. We first polymerized methyl sorbate (MS) initiated by NHC in N,N-dimethylformamide (DMF) at 25 °C, poly(MS) with a number-average molecular weight (Mn) of 3.5 × 103 (Mw/Mn = 2.1) was obtained with a conversion of 93%. The structure was confirmed by 1H and 13C NMR and IR spectra, which revealed that the propagation proceeded via 1,2-addition as well as 1,4-addition. Although the polymerization did not occur in toluene in the absence of any additive, quantitative monomer consumption was observed in the presence of methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD) to afford the poly(MS) with a 1,4-trans structure, 86% of threo diastereoselectivity, and a Mn of 23.0 × 103 with narrow molecular weight distribution (Mw/Mn = 1.17). From the matrix assisted laser desorption/ionization (MALDI-TOF) mass spectra of poly(MS) and the hydrogenated analogue, ring-closing occurred by nucleophilic attack of the anionic propagating center into the adjacent carbon of the α-terminal imidazolimium group to afford cyclic poly(MS). The cyclic formation in the present synthesis system was confirmed by DSC and viscosity measurements.

ChemInform Abstract: The Asymmetric Syntheses of Methyl D‐Digitoxoside (V)/(VI), L‐Oleandrose (X) and L‐Cymarose (XI)/(XII) from Methyl Sorbate, an Achiral Precursor.

AbstractAsymmetric syntheses of the title carbohydrates (mixtures of pyranoside and furanoside forms in some cases) starting from osmundolactone (I), derived from methyl sorbate, are described.

Facile Synthesis of Main-Chain Degradable Block Copolymers for Performance Enhanced Dismantlable Adhesion

Block copolymers consisting of readily degradable polyperoxides and non-degradable vinyl polymers as the block segments were successfully synthesized by reversible chain transfer catalyzed polymerization, which is one of living radical polymerization techniques. The block copolymers showed characteristic morphology and wettability being different from the polymer blends. When block copolymers containing polyperoxide and polymethacrylate blocks were heated below 150 °C, the polyperoxide blocks were completely degraded and the polymethacrylate blocks were recovered without degradation. Block copolymers containing a poly(2-ethylhexyl methacrylate) block were then investigated as a dismantlable adhesion material, which requires adequate bonding strength during use and easy debonding on demand. Among the several block copolymers, the one consisting of poly(2-ethylhexyl methacrylate) and polyperoxide from methyl sorbate (PPMS) (M(n) = 4900) exhibited good performance as a pressure-sensitive adhesive (PSA). After heating the test specimens in a temperature range from 60 to 100 °C, PSA performance, which was evaluated by 180° peel strength and shear holding power measurements, was significantly diminished. Especially, after heating at 100 °C for 1 h, spontaneous debonding of some test specimens was observed because of the evolution of volatile acetaldehyde from PPMS.

Electrochemical reduction of aliphatic conjugated dienes in the presence of carbon dioxide

A voltammetric and electrolytic study involved in the electroreductive carboxylation of multi-substituted aliphatic coujugated dienes has been successfully conducted. With methyl sorbate as the modal compound, acceptable yields of carboxylation and dimerization were achieved, which were influenced by various reaction conditions such as the supporting electrolyte, cathode nature, current density, charge passed and temperature. A correlation was first established between distinct electronic effects of the dienes and the electrochemical characteristics of their reduction and the distribution law of target products.

Cohesive Force Change Induced by Polyperoxide Degradation for Application to Dismantlable Adhesion

Polyperoxides containing peroxy bonds as the main-chain repeating units are a new class of degradable polymers because of significant changes in their molecular weight and physical properties during a degradation process. In this study, the application of linear and network polyperoxides to dismantlable adhesion was investigated. When the linear polyperoxide obtained from methyl sorbate and oxygen (PP-MS) was used as a pressure-sensitive adhesive (PSA), its shear holding power and 180° peel strength immediately decreased upon heating at 70 °C or under UV irradiation. Low-molecular-weight products, which were generated by the degradation of PP-MS, behaved as a plasticizer to effectively reduce the cohesive force. The adhesive properties of two types of polyperoxides-based network polymers, the cross-linking point and main-chain degradable network polymers, were evaluated. A cross-linking point degradable network polymer was produced by the oxygen cross-linking of dienyl-functionalized poly(ethylene glycol). A main-chain degradable network polymer was formed by the diisocyanate cross-linking of a hydroxy-functionalized polyperoxide. Both network polymers showed a higher adhesive strength than PP-MS due to their three-dimensional network structure. Noteworthy, the adhesive strength of the main-chain degradable network polymer was varied from the level of PSA to structural adhesives by increasing the added amount of the diisocyanate cross-linker. After heating at 110 °C, the cohesive and adhesive strengths significantly decreased. The linear and network polyperoxides are shown to be promising materials for dismantlable adhesion.

Developing an asymmetric, stereodivergent route to selected 6-deoxy-6-fluoro-hexoses

Free radical bromination and nucleophilic fluorination allows the conversion of methyl sorbate into the 6-fluoro analogue which undergoes sequential asymmetric dihydroxylation reactions. A range of 6-deoxy-6-fluorosugars were prepared by using different combinations of ligands. While the enantiomeric excesses obtained were comparable to those from other 6-substituted sorbates, the regioselectivity of dihydroxylation was moderate, with both 2,3- and 4,5-diols being obtained. A successful temporary persilylation strategy was evolved to convert the products of dihydroxylation rapidly to the fluorosugars 6-deoxy-6-fluoro-L-idose, 6-fluoro-L-fucose and 6-deoxy-6-fluoro-D-galactose, which were obtained in overall yields of 4%, 6% and 8% from methyl 6-fluoro-hexa-2E,4E-dienoate .

Chemoselective Cross‐Metathesis Reaction Between Electron‐Deficient 1,3‐Dienes and Olefins.

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Chemoselective cross-metathesis reaction between electron-deficient 1,3-dienes and olefins

Chemoselective cross-metathesis reactions between methyl sorbate or 1,3-dienic amides and various olefins in the presence of the Grubbs–Hoveyda catalyst have been investigated. Cross-metathesis reactions turned out to be more chemoselective with 1,3-dienic amides than with 1,3-dienic esters.

Photoinitiated polymerization of columnar stacks of self-assembled trialkyl-1,3,5-benzenetricarboxamide derivatives.

A disk-shaped molecule, N-(5-sorbyl-pentyl)-N',N"-di(n-octyl)benzene-1,3,5-tricarboxamide (1), has been synthesized and assembled into a columnar stack in cyclohexane. Using a photoinitiated process, we polymerized monomer 1 in its self-assembled state and analyzed the resulting poly-1. On cooling a boiling cyclohexane solution of 1, the molecules aggregate via amide hydrogen bonds, as supported by the position of the N-H stretching band in FT-IR spectroscopy. Evidence of helical columnar stacking of 1 in the aggregate is provided by an induced CD effect upon blending 1 with a chiral side-chain homologue 3 in a so-called "sergeants and soldiers" experiment. The columnar assembly in cyclohexane was polymerized by UV light (365 nm) irradiation in the presence of 2,2-dimethoxy-2-phenylacetophenone as radical photoinitiator. The polymerization occurs selectively to give 1,4-polymer with isolated trans C=C bonds, as shown by FT-IR, and (1)H and (13)C NMR spectroscopy. Lack of polymerization of methyl sorbate (4) under identical conditions, and low incorporation of 4 in copolymerizations with 1 in cyclohexane, suggests that the polymerization preferentially occurs within the columnar assembly. Size exclusion chromatography shows that the degree of polymerization (X(n)()) based on number average molecular weight is approximately 65. Incorporation of small amounts of nonpolymerizable derivatives 2 and 3 into the columns has no effect on X(n)() and conversion. Molecular models show that the polymerizable sidearm of 1 is long enough to span the distance between the monomers in the chiral stack. Under the atomic force microscope (AFM), purified samples of polymerized 1 displayed nanometer-sized fibrous morphologies with a high-axial-ratio (>150), uniform width (60 nm), and a thickness (1.0 nm) which corresponds to the width of the benzene tricarboxamide core of 1, whereas aggregates of nonpolymerized 1 yield a featureless image due to their instability.

Threo-Disyndiotactic Polymerization of (E,E)-Alkyl Sorbates Assisted by Bulky Organoaluminum Lewis Acid via “Alternating Turning over Polymerization (ATOP)” Mechanism

(E,E)-Methyl sorbate (MS) and (E,E)-ethyl sorbate (ES), i.e., methyl 2,4-hexadienoate and ethyl 2,4-hexadienoate, underwent anionic polymerization in toluene at −60 to 0 °C in the presence of organoaluminum Lewis acids. The NMR, wide-angle X-ray diffraction (WAXD), and semiempirical molecular orbital calculation demonstrated that 1,4-trans-threo-disyndiotactc polymerization occurred (tritactic polymerization). Coordination of methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD) (MAD/t-BuLi = 3) played three important roles, stabilization of the propagating anion, the activation of the monomer, and dissociation of tert-butyllithium (t-BuLi) aggregated in toluene to give polymers with relatively narrow molecular weight distribution (Mw/Mn = 1.3) using t-BuLi−(−)-menthyl ethyl ether (MEE) complex as the initiator. Hydrogenations of poly(MS) and poly(ES) with p-toluenesulfonylhydrazide (TSH) produced head-to-head (H−H) poly(propylene-alt-methyl acrylate) and poly(propylene-alt-ethyl acrylate), respectively, which enabled us to evaluate the stereochemistry including diastereoselectivity and stereoregularity of poly(alkyl sorbate)s in detail. The polymer from t-BuLi-MEE/MAD initiator system (at −60 °C) showed the highest stereospecificity, i.e., threo(99%)-disyndiotacticity(95%). The glass transition temperature of the threo poly(MS) is 27 °C with melting endotherm at 102 °C. The thermal property depends on the stereochemistry. Furthermore, we indicate that the polymerization proceed via “alternating turning over polymerization (ATOP)” mechanism, in which Lewis acid coordinated monomers are inserted into the propagating center with alternating turning over.

Degradable Polymers Prepared from Alkyl Sorbates and Oxygen under Atmospheric Conditions and Precise Evaluation of Their Thermal Properties

We report here the alternating copolymers of diene monomers with oxygen as a new class of degradable polymer with great potential. The alternating copolymers of alkyl sorbates with oxygen are efficiently prepared without decomposition under atmospheric conditions in the presence of an azo initiator. The produced alternating copolymers exothermically decompose upon heating in a similar mechanism irrespective of the kind of the ester alkyl group of the sorbates; i.e., the methyl, ethyl, octadecyl, and trifluoroethyl esters. The initial and maximum decomposition temperatures (Tinit and Tmax) are determined by differential thermal analysis (DTA) and thermogravimetric analysis (TG) in a nitrogen stream: Tinit = 106–112 °C (DTA), Tmax = 147–152 °C (DTA) or 144–148 °C (TG). The TG curves obtained at a different heating rate are kinetically analyzed to evaluate an activation energy for decomposition by several methods. The decomposition rate constants, as well as overall activation energy, for the polymeric peroxide obtained from methyl sorbate are also precisely determined during the isothermal decomposition in a temperature range of 80–120 °C by two different methods; Ea = 86.7 and 84.7 kJ mol-1 on the basis of the weight loss of the polymer monitored by TG analysis, and the change in the molecular weight of the polymer determined by gel permeation chromatography, respectively. It has been revealed that the thermal cleavage of the peroxy linkage and the subsequent successive β-scission produce fumaraldehyde monoester and acetaldehyde during the thermal decomposition of the alternating copolymers as the polymeric peroxides.