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This review focuses on summarising the studies on transition metal catalysed transfer vinylation of alcohols using vinyl ethers and vinyl acetate as vinylating agents. Mercury, palladium, iridium and gold catalysts are discussed herein. Selected examples from publications and patents are given for the purpose of analysing functional group tolerance towards the methodology. In addition, mechanistic pathways are described. [ABSTRACT FROM AUTHOR]

Despite the simplicity and abundance of ethylene, its practical application presents significant hurdles due to its nature as a highly flammable gas. Herein, a strategic use of easily handled vinyl ether is reported as a latent ethylene surrogate achieved via a spin‐center shift (SCS) pathway, enabling the successful three‐component reaction that bridges heteroarenes and various coupling partners, including sulfinates, thiols, and phosphine oxides. Through a photoredox catalytic process, α‐oxy radicals are generated by combining various radicals with phenyl vinyl ether, which are subsequently added to N‐heteroarenes. Subsequently, the radical‐mediated SCS pathway serves as the driving force for C─O bond cleavage, effectively engaging the phenoxy group as a leaving group. In addition, by broadening the utility of the method, a valuable synthon is provided for efficient C─H vinylation of N‐heteroarenes following sulfonyl group elimination. This approach not only enriches the toolbox of synthetic methodology but also provides a more streamlined alternative, circumventing the challenges associated with direct ethylene gas usage. The versatility of the method, particularly evident in late‐stage functionalizations of medicinally relevant molecules and peptides, underscores its capability to produce invaluable three‐component compounds and vinylated N‐heteroarene derivatives. [ABSTRACT FROM AUTHOR]

This article discusses a new synthetic approach for the exchange reaction between ketones and vinyl ethers using solid catalysts. The authors found that Amberlyst A16 and montmorillonite K10 were effective catalysts, resulting in moderate to good yields of the desired products. The catalysts could be reused multiple times without significant decrease in yield. The article also provides chemical analyses and data for various compounds, including NMR spectra, GC-MS data, and HRMS data. [Extracted from the article]

Vinyl ethers are valuable synthetic intermediates which are also found as natural products, including aflatoxins, rifamycins and plasmalogens. The latter are ubiquitous phospholipids in human cells and contain a vinyl ether moiety with specifically Z configuration. Although numerous methods are available for synthesis of vinyl ethers, there is a lack of methods for obtaining Z isomers of molecules of the type RCH=CHOR' that are applicable to plasmalogens. A variant of the Peterson reaction is described that generates such molecules with very high stereoselectivity (Z/E ratio: 99 : 1). (R,R)/(S,S)‐1‐alkoxy‐2‐hydroxyalkylsilanes were synthesized from 1‐trimethylsilylalkynes by a sequence of reduction with di‐isobutylaluminium hydride to a (Z)‐1‐trimethylsilylalkene, epoxidation of the alkene to a 2‐trimethylsilyl‐3‐substituted epoxide and regioselective, boron‐trifluoride catalyzed ring‐opening of the epoxide by reaction with an alcohol. Conversion of the (R,R)/(S,S)‐1‐alkoxy‐2‐hydroxyalkylsilanes to vinyl ethers (RCH=CHOR') was achieved under basic conditions as in a standard Peterson reaction. However, near exclusive formation of a Z vinyl ether was only achieved when the reaction was performed using potassium hydride in the non‐polar solvent α,α,α‐trifluorotoluene, more polar solvents giving increasing amounts of the E isomer. The sequence described embraces a variety of substituents and precursors, proceeds in overall high yield and is readily scalable. [ABSTRACT FROM AUTHOR]

Abstract Despite the simplicity and abundance of ethylene, its practical application presents significant hurdles due to its nature as a highly flammable gas. Herein, a strategic use of easily handled vinyl ether is reported as a latent ethylene surrogate achieved via a spin‐center shift (SCS) pathway, enabling the successful three‐component reaction that bridges heteroarenes and various coupling partners, including sulfinates, thiols, and phosphine oxides. Through a photoredox catalytic process, α‐oxy radicals are generated by combining various radicals with phenyl vinyl ether, which are subsequently added to N‐heteroarenes. Subsequently, the radical‐mediated SCS pathway serves as the driving force for C─O bond cleavage, effectively engaging the phenoxy group as a leaving group. In addition, by broadening the utility of the method, a valuable synthon is provided for efficient C─H vinylation of N‐heteroarenes following sulfonyl group elimination. This approach not only enriches the toolbox of synthetic methodology but also provides a more streamlined alternative, circumventing the challenges associated with direct ethylene gas usage. The versatility of the method, particularly evident in late‐stage functionalizations of medicinally relevant molecules and peptides, underscores its capability to produce invaluable three‐component compounds and vinylated N‐heteroarene derivatives.

Naphthalene‐ and phenanthrene‐fused [22]smaragdyrin BF2‐complexes were synthesized by 1) Suzuki‐Miyaura coupling of β‐brominated [22]smaragdyrin BF2 complexes with 2‐formylarylboronates, 2) Witting‐type methoxymethylenation of the formyl group, and 3) methanesulfonic acid‐catalyzed cyclization reaction. Subsequently these BF2 complexes were deboronized and oxidized to the corresponding antiaromatic [20]smaragdyrin free bases. The installed fused structures led to decrease of the aromatic characters of the [22]smaragdyrin BF2 complexes and the antiaromatic characters of the [20]smaragdyrin free bases. [ABSTRACT FROM AUTHOR]

In this work, we achieved a triggering degradation of polymers composed of carbon‐carbon (C−C) bonded backbone without relying on introduction of labile heteroatom‐based bond. The crucial point for the achievement is using vinyl ether (VE) as a comonomer in radical copolymerization of (meth)acrylate for introduction of the carbon‐hydrogen (C−H) bonds active for photocatalyzed hydrogen atom transfer (HAT) as triggers in the pendant. Interestingly, methyl methacrylate (MMA)‐n‐butyl vinyl ether (NBVE) copolymer underwent degradation in acetonitrile in the presence of benzophenone (Ph2CO) under UV irradiation at 80 °C. The degradation did not take place, when any one of UV, Ph2CO, heat, and NBVE unit was removed or HAT‐active solvent such as toluene and 1,4‐dioxane was used. These control experiments strongly supported the HAT‐triggering degradation. Furthermore, the degradation behaviors of the copolymers with other vinyl ethers such as tert‐butyl vinyl ether and methyl isopropenyl ether indicated that the C−H bond neighboring to oxygen on the pendant is mainly responsible for the trigger leading to degradation. The HAT‐triggering degradation was also demonstrated even with the acrylate‐based copolymer. [ABSTRACT FROM AUTHOR]

The iron‐containing imidazolium‐based ionic liquids (ILs) 1‐n‐butyl‐3‐methylimidazolium heptachlorodiferrate (BMI.Fe2Cl7) and 1‐n‐butyl‐3‐methylimidazolium tetrachloroferrate (BMI.FeCl4) are applied as catalysts in the homogeneous polymerization of n‐butyl vinyl ether. Both solventless conditions as well as using different organic solvents, catalyst concentrations, temperatures, and reaction times are tested to assess the polymerization conditions that lead to the highest molecular weights of poly(n‐butyl vinyl ether). The Lewis acidic IL BMI.Fe2Cl7 proves to be highly efficient, even at low catalyst concentrations. In bulk polymerization, polymers with 142 kg mol−1 are obtained using a 1:10000 molar ratio of catalyst to monomer. In solution polymerization, the monomer consumption is also rapid and the molecular weight of the polymer is related to the catalyst concentration used. These results indicate the potential of this catalyst for industrial applications. In contrast with the acidic IL, the neutral iron‐containing imidazolium‐based IL BMI.FeCl4 does not show any catalytic activity. [ABSTRACT FROM AUTHOR]

The development of polymers with on‐demand degradability is required to alleviate the current global issues on polymer‐waste pollution. Therefore, we designed a vinyl ether monomer with an o‐nitrobenzyl (oNBn) group as a photo‐deprotectable pendant (oNBnVE) and synthesized an alternating copolymer with an oNBn‐capped acetal backbone via cationic copolymerization with p‐tolualdehyde (pMeBzA). The resultant alternating copolymer could be rapidly degraded into lower‐molecular‐weight compounds upon simple exposure to UV irradiation without any reactants or catalysts, while it was sufficiently stable toward heat and ambient light. This degradation proceeds via cleavage of the hemiacetal structure generated upon photo‐deprotection of the oNBn pendant. The oNBn‐peculiar degradability allowed the exclusive photo‐degradation of the oNBnVE/pMeBzA segments in a diblock copolymer composed of oNBnVE/pMeBzA and benzyl vinyl ether (BnVE)/pMeBzA segments. [ABSTRACT FROM AUTHOR]

We report a novel method to synthesize degradable poly(vinyl ether)s with cleavable thioacetal bonds periodically arranged in the main chains using controlled cationic copolymerization of vinyl ethers with a 7‐membered cyclic thioacetal (7‐CTA) via degenerative chain transfer (DT) to the internal thioacetal bonds. The thioacetal bonds, which are introduced into the main chain by cationic ring‐opening copolymerization of 7‐CTA with vinyl ethers, serve as in‐chain dormant species to allow homogeneous propagation of vinyl ethers for all internal segments to afford copolymers with controlled overall and segmental molecular weights. The obtained polymers can be degraded into low‐ and controlled‐molecular‐weight polymers with narrow molecular weight distributions via hydrolysis. Various vinyl ethers with hydrophobic, hydrophilic, and functional pendants are available. Finally, one‐pot synthesis of multiblock copolymers and their degradation into diblock copolymers are also achieved. [ABSTRACT FROM AUTHOR]

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The synthesis of new functionalized vinyl ethers (VEs) by transetherification reaction between ethyl vinyl ether (EVE) and different alcohols is presented. An air-stable palladium catalyst generated in situ efficiently catalyzed the reaction leading to various VEs in a single step with good alcohol conversion (50–82%) and good VE yields (up to 75%). The reaction conditions were optimized in terms of the initial EVE/alcohol molar ratio, alcohol concentration, solvent, presence and nature of the ligand, amount of the catalyst, and choice of the metal precursor. All VEs were characterized using $^{1}$H and $^{13}$C NMR spectroscopy.

This article reports a comprehensive theoretical study of electron scattering from vinyl ether and its isomers. The electron–molecule quantum collision problem is solved through a complex optical potential approach. From the solution of the Schrödinger equation corresponding to this scattering problem, various cross sections were obtained for energies from ionization threshold of target to 5 keV. To deal with the non-spherical and complex structure, a multi-center group additivity approach is used. Furthermore, geometrical screening correction is applied to compensate for the overestimation of results due to electron charge density overlap. We found an interesting correlation between maximum ionization cross section with polarizability and ionization energy of the target molecule. The fitting of the total cross section as a function of the incident electron energy is reported in this article. The correlation between the effective diameter of the target and the projectile wavelength at maximum ionization energy is also reported for vinyl ether and its isomers. The data presented here will be useful to biomedical field, mass spectrometry, and chemical database for military range applications. The cross sections are also important to model Mars's atmosphere due to their presence in its atmosphere. The gas-kinetic radius and the van der Waals coefficients are estimated from the electron-impact total scattering cross sections. In addition, the current study predicts the presence of isomeric effects in the cross section. [ABSTRACT FROM AUTHOR]

The living cationic polymerizations of sulfide-containing vinyl ethers, namely, alkyl-sulfide-containing 2-(ethylthio)ethyl vinyl ether (ESEVE) and arylsulfide-containing 2-(phenylthio)ethyl and 2-[4-(methylthio)phenoxy]ethyl vinyl ethers (PSEVE and MSPEVE, respectively), were examined using HCl/ZnCl2, 1-(isobutoxy)ethyl acetate (IBEA)/Et1.5AlCl1.5, and IBEA /Et1.5AlCl1.5/SnCl4 as initiators. The polymerization of ESEVE terminated at a 35% monomer conversion, and a high-molecular-weight polymer was not obtained; instead, the nucleophilicity of the sulfur moiety in ESEVE led to cyclization, forming five-membered ring sulfonium species. In contrast, the side reactions were suppressed when PSEVE was used, which has a less-nucleophilic sulfur moiety on its benzene ring, and polymerization proceeded to an 88% conversion, affording a high-molecular-weight polymer with a narrow molecular weight distribution (Mw = 12,500, Mw/Mn = 1.18). Furthermore, cyclic sulfonium was not produced during the polymerization of MSPEVE, in which the sulfur atom was farther from the generated carbocation; the polymerization proceeded quantitatively producing a high-molecular-weight polymer with a narrow molecular weight distribution, despite the short lifetime of the growing species. In particular, a high-molecular-weight polymer with the narrowest distribution (Mw = 13,500, Mw/Mn = 1.08) was obtained when SnCl4 was used as the Lewis acid. [ABSTRACT FROM AUTHOR]

A novel strategy for synthesizing a series of multiblock copolymers is developed by combining radical/cationic step‐growth polymerizations of dithiols and divinyl ethers and chain‐growth cationic degenerative chain‐transfer (DT) polymerizations of vinyl ethers using thioacetals as key components. The combination of radical step‐growth polymerization and a cationic thiol‐ene reaction or cationic step‐growth polymerization enables the synthesis of a series of macro chain‐transfer agents (CTAs) composed of poly(thioether) and thioacetal groups at different positions. The resulting products are 1) bifunctional macro CTAs with thioacetal groups at both chain ends, 2) periodic macro CTAs periodically having thioacetal groups in the main chain, and 3) random macro CTAs randomly having thioacetal groups in the main chain. Subsequently, the obtained macro CTAs are used for chain‐growth cationic DT polymerization of methoxyethyl vinyl ether (MOVE) to result in 1) triblock, 2) periodic, and 3) random multiblock copolymers consisting of poly(thioether) and poly(MOVE) segments. All these triblock and multiblock copolymers composed of hydrophobic poly(thioether) and hydrophilic poly(MOVE) segments show an amphiphilic tendency to form characteristic micelles in aqueous solutions. In addition, due to the thermoresponsive poly(MOVE) segments, the obtained copolymers exhibit lower critical solution temperatures that depend on the segment sequences and lengths. [ABSTRACT FROM AUTHOR]

A concise synthesis of a plasmenylethanolamine (PlsEtn-[16:0/18:1 n-9]), known as antioxidative phospholipids commonly found in cell membranes, has been achieved from an optically active known diol through 8 steps. The key transformations for the synthesis of PlsEtn-[16:0/18:1 n-9] are (1) regio- and Z -selective vinyl ether formation via the alkylation of a lithioalkoxy allyl intermediate with an alkyl iodide, and (2) a one-pot phosphite esterification–oxidation sequence to construct the ethanolamine phosphonate moiety in the presence of the vinyl ether functionality. The piperidine salt of synthetic PlsEtn-[16:0/18:1 n-9] was desalinated through reversed-phase high-performance liquid chromatography purification. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thiophosphoramide hydrogen bond donor catalyzes ambient cationic polymerizations. • Accelerates initiation with weakly to strongly coordinating counteranions. • Ionization at chain end promotes propagation for underutilized counteranions. • Applied to photoinitiated and Brønsted acid cationic polymerizations. • Increased polymerization rate investigated by NMR titrations and DFT optimizations. Photoacid generators (PAGs) have facilitated a number of technology breakthroughs in the electronic, coating, and additive manufacturing industries. Traditionally, PAGs that contain weakly coordinating anions, such as PF 6 −, generate Brønsted superacids under UV irradiation for rapid cationic polymerizations. However, PAGs with strongly coordinating anions remain under-utilized as they form weak acids that are inefficient or even incapable of initiating polymerization. To expand the scope of potential counteranions in PAGs, we leveraged a thiophosphoramide hydrogen bond donor (HBD) to catalyze photoinitiated cationic polymerizations from diphenyliodonium PAGs. Through the formation of hydrogen bonds between the HBD and PAG counteranion, acceleration of the polymerization rate was observed for a range of non-coordinating and coordinating anions. The effect of the HBD on the polymerization kinetics was investigated by 1H − NMR titrations and geometry optimizations. Extending HBD catalysis beyond photopolymerizations, addition of HBD also enabled hydrochloric acid to initiate controlled reversible addition − fragmentation chain transfer (RAFT) polymerization under ambient conditions. With the versatility of HBD, there is potential to access initiation systems that were previously believed to be impractical for cationic polymerization. [ABSTRACT FROM AUTHOR]

This article reports a comprehensive theoretical study of electron scattering from vinyl ether and its isomers. The electron–molecule quantum collision problem is solved through a complex optical potential approach. From the solution of the Schrödinger equation corresponding to this scattering problem, various cross sections were obtained for energies from ionization threshold of target to 5 keV. To deal with the non-spherical and complex structure, a multi-center group additivity approach is used. Furthermore, geometrical screening correction is applied to compensate for the overestimation of results due to electron charge density overlap. We found an interesting correlation between maximum ionization cross section with polarizability and ionization energy of the target molecule. The fitting of the total cross section as a function of the incident electron energy is reported in this article. The correlation between the effective diameter of the target and the projectile wavelength at maximum ionization energy is also reported for vinyl ether and its isomers. The data presented here will be useful to biomedical field, mass spectrometry, and chemical database for military range applications. The cross sections are also important to model Mars’s atmosphere due to their presence in its atmosphere. The gas-kinetic radius and the van der Waals coefficients are estimated from the electron-impact total scattering cross sections. In addition, the current study predicts the presence of isomeric effects in the cross section.

Inclusion of a silyl ketene acetal in the non-living cationic polymerisations of methyl and isobutyl vinyl ether provides polymers with ester end groups. The use of an ab initio approach produces materials with high degrees of chain end functionality provided the reaction temperature, monomer concentration and concentration of silyl ketene acetal are optimised. Optimisation, studied mainly by the use of MALDI-ToF mass spectrometry, involved obtaining reaction conditions in which the dominant termination reaction was alkylation of the silyl ketene acetal then rapid desilation produced the ester end groups. [ABSTRACT FROM AUTHOR]

Three bidentate phosphoramidite ligands were synthesized, characterized, and employed in Rh‐catalyzed hydroformylation of vinyl ethers. The complex Rh(acac)(2,2′‐bis{(di[1H‐indol‐1‐yl]phosphanyl)oxy}‐1,1′‐binaphthalene} (acac = acetylacetone) (Rh‐L4) was also synthesized and characterized. Rh‐L4 showed good regioselectivity for the hydroformylation of vinyl ethers under mild reaction conditions: 2 MPa of syngas, 1:1 (H2/CO) substrate/catalyst molar ratio 1000:1, and 60 °C. The linear selectivity was up to 98%, and in most cases was about 80%, with no hydrogenation product formation observed, which could be a potential way to synthesize 1,3‐propanediol. A mechanism study including density functional theory computational analysis showed that both Rh–H and CO insertion steps in the hydroformylation of vinyl ether were linear‐preferred in our catalyst system. [ABSTRACT FROM AUTHOR]

The use of calcium carbide (in the presence of H2O) as a source of acetylene in the reaction with methyl 2-amino-4,6-O-benzylidene-2-deoxy-β-d-glucopyranoside under superbasic conditions (KF, KOH, DMSO, 130 °C, 3 h) led to the corresponding vinyl ether in 78% yield. The vinylation does not affect other reaction centers. Replacement of water with deuterium oxide in the reaction mixture gave a stable deuterated analog of this vinyl ether in 72% yield. The one-step isotopic enrichment was practically quantitative (isotopic purity >96%). Introduced deuterium atoms can be used as a convenient label in further transformations. [ABSTRACT FROM AUTHOR]

The transformations of 7-dimethylaminomethyl-6-hydroxyaurone and 5-dimethylaminomethyl-6-hydroxy-7-methylurone in the inversed electron-demand hetero-Diels–Alder reaction were studied. As a result of in situ thermal formation of o-quinone methides containing the benzofuranone moiety and cycloaddition of cyclic vinyl esters, 2-benzylidene derivatives of difuro[2,3-b:2',3'-f]chromen-3(2H)-one, furo[2,3-f]pyrano[2,3-b]chromen-3(2H)-one, difuro[2,3-b:3',2'-g]chromen-3(2H)-one, and furo[3,2-g]pyrano[2,3-b]chromen-3(2H)-one heterocyclic systems were synthesized. A similar reaction with cyclic enamines, accompanied by subsequent transformation of hemi-aminals, led to the formation of partially hydrogenated derivatives of furo[2,3-a]xanthen-3(2H)-one and furo[3,2-b]xanthen-3(2H)-one. [ABSTRACT FROM AUTHOR]

In this work, the thiol‐ene click reaction is employed to fabricate polymer‐dispersed liquid crystal (PDLC) films by photoinitiated polymerization. The PDLC films are prepared by systematic variation of key conditions: variety and content of ‐ene monomer, liquid crystal (LC) content, curing time, and curing light intensity. We find that both the morphologies and electro‐optic properties of these films are adjustable. When increasing the length of alkyl main chain of ‐ene monomers, the driving voltages reduce, but in turn, the contrast ratio decreases. Increasing ‐ene monomer content raises the driving voltages as well as the response time, and the increase of LC content lowers the driving voltages but has a negative effect on the contrast ratio. The changes to the curing conditions (both curing time and UV light intensity) can be used to modify the driving voltages, response time, and contrast ratios of PDLC films. These comparative studies will elucidate new insights in commercial applications of intelligent PDLC films. [ABSTRACT FROM AUTHOR]

Naphthalene- and phenanthrene-fused [22]smaragdyrin BF 2 -complexes were synthesized by 1) Suzuki-Miyaura coupling of β-brominated [22]smaragdyrin BF 2 complexes with 2-formylarylboronates, 2) Witting-type methoxymethylenation of the formyl group, and 3) methanesulfonic acid-catalyzed cyclization reaction. Subsequently these BF 2 complexes were deboronized and oxidized to the corresponding antiaromatic [20]smaragdyrin free bases. The installed fused structures led to decrease of the aromatic characters of the [22]smaragdyrin BF 2 complexes and the antiaromatic characters of the [20]smaragdyrin free bases., (© 2023 Wiley-VCH GmbH.)

Vibrio campbellii is a major pathogen in aquaculture. It is a causative agent of the so-called “luminescent vibriosis,” a life-threatening condition caused by bioluminescent Vibrio spp. that often involves mass mortality of farmed shrimps. The emergence of multidrug resistant Vibrio strains raises a concern and poses a challenge for the treatment of this infection in the coming years. Inhibition of bacterial cell-to-cell communication or quorum sensing (QS) has been proposed as an alternative to antibiotic therapies. Aiming to identify novel QS disruptors, the 9H-fluroen-9yl vinyl ether derivative SAM461 was found to thwart V. campbellii bioluminescence, a QS-regulated phenotype. Phenotypic and gene expression analyses revealed, however, that the mode of action of SAM461 was unrelated to QS inhibition. Further evaluation with purified Vibrio fischeri and NanoLuc luciferases revealed enzymatic inhibition at micromolar concentrations. In silico analysis by molecular docking suggested binding of SAM461 in the active site cavities of both luciferase enzymes. Subsequent in vivo testing of SAM461 with gnotobiotic Artemia franciscana nauplii demonstrated naupliar protection against V. campbellii infection at low micromolar concentrations. Taken together, these findings suggest that suppression of luciferase activity could constitute a novel paradigm in the development of alternative anti-infective chemotherapies against luminescent vibriosis, and pave the ground for the chemical synthesis and biological characterization of derivatives with promising antimicrobial prospects.

Mixtures of a weak protonic acid and a trace amount of superstrong protonic acid were used for the simple control of the cationic polymerization of vinyl ethers via a degenerative chain-transfer mechanism, in which the former acid works as a precursor of the chain transfer agent (CTA) or the dormant species and the latter works as a source of the cationic propagating species. The addition of mixtures of phosphoric acid dibutyl ester ((n-BuO)2PO2H) or 1-octanethiol (n-C8H17SH) and a trace amount of trifluoromethanesulfonic acid (TfOH) to a solution of isobutyl vinyl ether (IBVE) at −78 °C resulted in polymers with controlled molecular weights, which were basically determined by the feed ratio of IBVE to the weak protonic acid, and narrow molecular weight distributions (Mw/Mn ≈ 1.1). These results were almost the same as those obtained using their prepared adducts of IBVE as CTAs in the presence of a trace amount of TfOH under similar conditions. Methanesulfonic acid (CH3SO3H), whose adduct of IBVE has not been isolated due to instability, was similarly used in conjunction with trace TfOH to result in controlled molecular weights but slightly broader MWDs (Mw/Mn = 1.2–1.8). These results indicate that the sulfoxonium ion is also an effective intermediate in the cationic DT polymerization in addition to the phosphonium and sulfonium intermediates derived from (n-BuO)2PO2H and n-C8H17SH, respectively. The simple living cationic polymerization was thus achieved by using a combination of a weak protonic acid and a trace amount of TfOH, which are both easily available, low cost, free from metal, and easy to handle, without need for preparation of the initiator. [ABSTRACT FROM AUTHOR]

The intramolecular asymmetric photocycloaddition between 1,4‐naphthoquinone and vinyl ether with a small (R)‐point‐chiral group on the tether was studied. Under photoirradiation, [2+2] cyclobutane products were exclusively obtained for this intramolecular system. The effect of solvent polarity on the stereoselectivity was significant, with predominant formation of the (2R,S3) over the (2R,R3) isomer in non‐polar solvents being reversed in slightly polar dichloromethane. The detailed temperature‐dependent study revealed the dominant diastereo‐differentiating processes, which were switched between the ground‐state equilibrium, the relative rate of bond formation in the triplet manifold, as well as deactivation processes between the pro‐(S3) and pro‐(R3) precursors, depending on the temperature domain examined. The enthalpic contribution (ΔΔH≠) was always compensated by the entropic factor (ΔΔS≠), implying the importance of solvation on the diastereo‐differentiation steps. The mechanism of photocycloaddition, especially for the face‐selective processes, is thoroughly discussed, which is supported by quantum chemical calculations on the ground‐state circular dichroism (CD) spectral behavior as well as on the diastereomeric transition states in the triplet excited state. [ABSTRACT FROM AUTHOR]

Background. Vinyl esters of carboxylic acids are widely used as solvents in the chemical industry, additives in the food industry, monomers in the preparation of composite materials, initial compounds in organic synthesis. Carboxylic acids and polymers based on them have adhesion properties and are used in the preparation of materials that protect various surfaces. On the basis of divinyl ethers low-toxic biomaterials are synthesized by photopolymerization. Purpose. Synthesis of the corresponding vinyl esters in homogeneous conditions based on the reaction of benzoic anhydride containing various substituents in the aromatic ring with vinyl acetate. The study of the influence of the nature of substances on the product yield was carried out. Methodology. Vinyl ether by reacting aromatic carboxylic anhydride with potassium vinyl acetate, obtained by reacting potassium tertiary butylate (t-BuOK) with vinyl acetate was synthesised. The structure of the synthesized compounds was confirmed by spectral analysis of FTIR, 1H-NMR, 13C-NMR. Originality. As a result of the reaction of benzoyl anhydrides containing various substituents in the aromatic ring, with vinyl potassium vinyl acetate, vinyl ethers were synthesized without catalysis. The mechanism of influence of ions of vinyloxide is grounded. Findings. Vinyl esters of benzoic acid, which contain various substituents in the aromatic ring, have been synthesized. The influence of the nature of the compounds and their molar ratio on the yield of vinyl ether is determined. [ABSTRACT FROM AUTHOR]

Highlights • Non-phenolic lignin model dimer gives vinyl ether and C β =O monomer. • Vinyl ether is readily hydrolyzed into C β =O monomer. • Phenolic dimer decomposes in different pathways. • Vinyl ether from phenolic dimer gives C α =C β monomer. • Formation of homovanillin and cinnamyl alcohols from natural lignin. Abstract Radical chain reactions of a β-ether-type lignin model dimer, 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)-1-propanol, were reinvestigated at 350 °C in closed ampoule reactors under the influence of wood (Japanese cedar) pyrolysis. The formation of vinyl ether dimers and C β =O monomers was observed in addition to previously reported C α =C β and C α =O monomers and veratraldehyde. The vinyl ether dimer was readily hydrolyzed to the C β =O monomer, which suggests that the formation of the C β =O-type monomers, such as homovanillin from natural lignin pyrolysis, originates from the vinyl ether intermediates. Unlike the non-phenolic dimer, the corresponding phenolic dimer did not form the vinyl ether dimer and C β =O monomer. The results, when using C β -deuterium-labeled dimers, suggest that a portion of the C α =C β monomer from the phenolic dimer forms via the vinyl ether intermediate, probably through conversion into quinone methide, in which the bond dissociation energy of C β ‒O is reduced (19.1 kcal mol−1 by density functional theory calculations). This leads to the simultaneous homolytic cleavage of the C β ‒O bond to form the C α =C β monomer. Such reactions did not proceed in the pyrolysis of the non-phenolic dimer, which is not able to form the stable quinone methide intermediate. This study can provide insight into the pyrolytic conversion of lignin, particularly the formation of C β =O- and C α =C β -types monomer. [ABSTRACT FROM AUTHOR]

Vibrio campbellii is a major pathogen in aquaculture. It is a causative agent of the so-called "luminescent vibriosis," a life-threatening condition caused by bioluminescent Vibrio spp. that often involves mass mortality of farmed shrimps. The emergence of multidrug resistant Vibrio strains raises a concern and poses a challenge for the treatment of this infection in the coming years. Inhibition of bacterial cell-to-cell communication or quorum sensing (QS) has been proposed as an alternative to antibiotic therapies. Aiming to identify novel QS disruptors, the 9H-fluroen-9yl vinyl ether derivative SAM461 was found to thwart V. campbellii bioluminescence, a QS-regulated phenotype. Phenotypic and gene expression analyses revealed, however, that the mode of action of SAM461 was unrelated to QS inhibition. Further evaluation with purified Vibrio fischeri and NanoLuc luciferases revealed enzymatic inhibition at micromolar concentrations. In silico analysis by molecular docking suggested binding of SAM461 in the active site cavities of both luciferase enzymes. Subsequent in vivo testing of SAM461 with gnotobiotic Artemia franciscana nauplii demonstrated naupliar protection against V. campbellii infection at low micromolar concentrations. Taken together, these findings suggest that suppression of luciferase activity could constitute a novel paradigm in the development of alternative anti-infective chemotherapies against luminescent vibriosis, and pave the ground for the chemical synthesis and biological characterization of derivatives with promising antimicrobial prospects. [ABSTRACT FROM AUTHOR]

The reaction of [(Cp*Ir)2(μ-dmpm)(μ-H)][OTf] (2) [Cp* = η5-C5Me5, dmpm = bis(dimethylphosphino)methane] with 2,3-dihydrofuran gives [(Cp*IrH)2(μ-dmpm){μ-(2,3-dihydrofuranyl)}][OTf] (3) in an isolated yield of 70% via the C−H bond activation at the 5-position of 2,3-dihydrofuran. Complex 3 is slowly converted into [(Cp*Ir)2(μ-dmpm)(μ-C=C(H)CH2CH2OH)][OTf] (4) quantitatively via the proton-mediated C−O bond activation. The reaction of 2 with ethyl vinyl ether gives [(Cp*Ir)2(μ-dmpm)(μ-CH=CH2)][OTf] (5) in the isolated yield of 64% via the successive activation of C−H and C−O bonds.