Hydroxy-, Methoxymercuration and Lewis Acid Catalyzed Formyloxylation of Methyl Linoleate

Methyl linoleate (1) reacts by hydroxymercuration-demercuration to methyl hydroxyoctadecenoates (2) of the ricinolic acid type and tetrahydrofurans 4, 5. Good yields of 4,5 are favored by high concentrations of 1 and reagents and reflux temperature. Methyl ricinolate cyclizes in an analogous reaction nearly quantitatively to 4 with a high diastereoselectivity in favor of the syn-isomer. The methoxymercuration-demercuration leads to mono- and dimethoxy adducts. Mercury(II) acetate can be substituted for nontoxic electrophiles. 1 affords in formic acid with BF₃-etherate or HBF₄ as Lewis acids the mono- and diformiates in a ratio of 1:1 and 77% yield. In contrast to the oxymercuration, however, this addition is fairly regiounselective.     

Thermoinitiated cationic polymerization of epoxy resins by sulfonium salts

Catalytic activities of benzyl sulfonium salts with nonnucleophilic anions (BF₄^?,PF₆^?,AsF₆^?,SbF₆^?) for epoxy polymerization were examined. The order of reactivities correlated well with nonnucleophilicity of anions. Epoxy resins catalyzed by these salts are characterized by longer shelf-life and shorter gel time at high temperature. Some physical properties of cured product were compared with those cured by a commonly used BF₃ amine complex.     

1H, 19F and 11B nuclear magnetic resonance characterization of BF3: amine catalysts used in the cure of C fibre-epoxy prepregs

¹H, ¹⁹F and ¹¹B nuclear magnetic resonance studies are reported which characterize the complexes of boron trifluoride with monoethylamine and with piperidine, BF₃:NH₂C₂H₅ and BF₃:NHC₅H₁₀, respectively. These complexes are used as catalysts for the cure of high performance C fibre-epoxy composities from prepregs. The chemical compositions of commercial BF₃:amine complexes are variable and contain BF₄^? and BF₃(OH)^? salts together with other unidentified highly reactive species. The BF₃:amine complexes, which are susceptible to hydrolysis, also partially convert to the BF₄^? salt (i.e. BF₄^?NH₃⁺C₂H₅) upon heating. This salt formation is accelerated in dimethyl sulphoxide solution and in the presence of the epoxides that are present in commercial prepregs. Commercial C fibre-epoxy prepregs are shown to contain either BF₃:NH₂C₂H₅ or BF₃:NHC₅H₁₀ species together with their BF₄^? salts and a variety of boron-fluorine or carbon-fluorine prepreg species. Considerable variation in the relative quantities of BF₃:amine to its BF₄^? salt was observed from prepreg lot to lot, which will cause variable viscosity-time-temperature prepreg cure profiles. It is concluded that the chemically stable and mobile BF₄^? salt is the predominant catalytic species, acting as a cationic catalyst for the prepreg cure reactions. During the early stages of cure the BF₃:amine catalysts convert to the BF₄^? salts in the presence of epoxides, whereas the BF₃-prepreg species are susceptible to catalytic deactivation and immobilization.     

Luminescence of some simple tetracoordinate organoboron complexes in solution. Fluorescence from ligand to ligand CT states

The Lewis base–Lewis acid adducts with the Lewis bases pyrazine, triphenyphosphine, neocuproine (2,9-dimethyl-1,10-phenanthroline), cuproine (2,2′-diquinolyl) and triphenylborane as Lewis acid were prepared. Their electronic spectra are characterized by low-energy electronic transitions which are attributed to phenyl (BPh₃) to Lewis base, ligand to ligand charge transfer (LLCT) transitions. These Lewis base-BPh₃ complexes display a distinct blue to green fluorescence in solution which originates from the lowest-energy LLCT singlets.     

Formation of Polymeric Lewis Acid–Lewis Base Complexes with Well-defined Organoboron Polymers

The binding of Lewis bases to organoboron polymeric Lewis acids has been studied and the parameters that determine the complexation equilibrium have been investigated, which include (i) the strength of the individual Lewis acids and Lewis bases, (ii) concentration, and (iii) temperature. While the strongly Lewis acidic borane polymers poly(4-bis(pentafluorophenyl)borylstyrene) (PS-BPf) and poly(4-(di-2-thienylboryl)styrene) (PS-BTh) form isolable complexes with strong Lewis bases such as 4-t-butylpyridine (^tPy), a temperature dependent equilibrium is established with weaker bases such as THF. Similarly, the weakly Lewis acidic boronate polymer poly(4-diethoxyborylstyrene) (PS-BOEt) undergoes a temperature dependent equilibrium with the strong Lewis base 4-dimethylaminopyridine (DMAP), while poly(4-pinacolatoborylstyrene) (PS-BPin) does not significantly bind to pyridine bases. Decomplexation of PS-BTh· ^t Py is achieved by treatment with the stronger Lewis acid, B(C₆F₅)₃, thereby confirming the reversible nature of the polymeric Lewis acid–base adducts. This paper is dedicated to Professor Ian Manners in gratitude of his guidance throughout the years and recognition of his scientific accomplishments     

Polyaniline Salts and Complexes as Catalyst in Bisindole Synthesis

Polyaniline salts are prepared by doping of polyaniline base with different Bronsted acids (H₂SO₄, HNO₃ and H₃PO₄), organic acid — p-toluene sulfonic acid (PTSA) and Iodine (I₂). Polyaniline complexes are also prepared using Lewis acids (BF₃, AlCl₃ and SnCl₂). Polyaniline salts and polyaniline complexes are characterized by physical, electrical and spectral methods. Polyaniline salts and polyaniline complexes are used as catalyst for the first time in bisindole synthesis. Bisindole (3,3′-bis(indolyl)phenylmethane) is obtained in excellent yields with simple and more environmental benign procedure. The use of polyaniline catalysts are feasible because of their easy preparation, easy handling, stability, easy recovery, reusability, good activity and eco-friendly.     

A study on designing a paired electrolysis for electro-induced Michael addition using tetrafluoroborate-based ionic liquid as electrolysis medium and pre-catalyst in a divided cell

Simultaneous double electro-induced synthesis of Michael adducts in both the compartments of a divided cell has been achieved by galvanostatic electrolysis in 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid, exploiting the direct electro-generation of the enolate in the cathodic side and the electro-generation of the Lewis acid BF₃ in the anodic side of the cell.     

Effect of temperature,solvent, Lewis acid and additives on the polymerization of tert‐butyl vinyl ether using Lewis acid‐induced N‐methyleneamines as cationic initiators

N‐Methyleneamines, formed by treating 1,3,5‐trimethylhexahydro‐1,3,5‐triazines with Lewis acids, have been shown to be capable initiators in the cationic polymerization of tert‐butyl vinyl ether, yielding polymers with amine functionality at the chain ends. Previous work was limited to titanium(IV) chloride (TiCl₄) as the Lewis acid in dichloromethane solvent at 0 °C (with resulting polymers possessing relatively broad polydispersity index (PDI) values near 2), while this contribution details the effect of reaction parameters on the polymeric products; specifically, the role of temperature, solvent, Lewis acid and additives. Ultimately, performing the polymerization at ?78 °C in dichloromethane with TiCl₄ as the Lewis acid and tetra‐n‐butylammonium chloride (nBu₄NCl) as the additive afforded the best control over the system, with polymers formed possessing low PDI values (<1.2). Dramatic changes in number‐average molecular weight and PDI were observed in polymers formed by initiating systems of Lewis acid‐induced N‐methyleneamines, with temperature, solvent, Lewis acid and additives all playing a role. By varying single parameters, optimization of the system was achieved. Copyright © 2009 Society of Chemical Industry     

Amination of Polyethylene Glycol to Polyetheramine over the Supported Nickel Catalysts

Surface nickel (NiO _x ) species, surface NiAl _x O _y compound, and NiO crystallites are present on the Ni/Al₂O₃ catalysts, and the ratio of these nickel species is dependent on the nickel loading. Surface nickel interacts with the TiO₂ support to form a surface nickel titanate compound (NiTiO _x ) which has a lower reducibility. The weak interaction between the surface nickel and the silica support results in the formation of NiO crystallites on the SiO₂ surface. The Ni/Al₂O₃ and Ni/TiO₂ catalysts contain new surface Lewis acid sites and the amount of surface Lewis acid sites increases with increasing nickel concentration. The Ni/SiO₂ catalysts have no sign of the presence of the surface Lewis acid sites. Only the Ni/Al₂O₃ catalysts have shown the ammonia adsorption at temperature of 200°C. Supported nickel on alumina catalysts possess the highest amination conversion, and the amine yield increases with increasing nickel loading up to 15% and starts to level off. By comparing amination catalysis with quantitatively TPR studies of the H₂ consumed of the Ni/Al₂O₃ catalysts, it appears that the dispersed nickel species are the active sites for amination. In addition, the amination product is mainly the secondary amine due to the presence of water.     

Epoxy/imidazolium-based ionic liquid systems: The effect of the hardener on the curing behavior,thermal stability,and microwave absorbing properties

A new transparent microwave absorbing coating was developed by compounding 1-butyl-3-methyl imidazolium tetrafluoroborate (bmim.BF₄) ionic liquid (IL) with diglycidyl ether of bisphenol A-type epoxy resin. The systems were crosslinked with the IL alone or combined with conventional hardeners, as anhydride or aromatic amine. The curing behavior was investigated by thermal and spectroscopic analysis performed at high temperatures. Neat bmim.BF₄ was able to cure epoxy resin, giving rise to networks with outstanding thermal stability compared with the systems cured with anhydride or aromatic amine. bmim.BF₄ accelerated the curing process in the presence of aromatic amine but retarded this event when anhydride was used as an external curing agent. The glass-transition temperature evaluated by dynamic mechanical analysis decreased when the amount of IL increased, which can be attributed to side reactions during the curing process, as well as the plasticizing effect of IL. The epoxy networks cured with bmim.BF₄ alone or in combination with anhydride or aromatic amine were transparent and presented considerable microwave absorbing properties in the X-band frequency range (8–12 GHz), being the best performance observed for the systems cured with bmim.BF4/anhydride curing system, with reflection loss value around −16 dB at 11.3 GHz. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48326.     

Removal of aldehydes by amino acids and their salts in ambient air

The removal of gaseous aldehydes by amino acids and by their sodium salts and hydrochlorides was studied in ambient air with the relative humidity of 30% at 25°C. Amino acid sodium salts, diamino acids, sodium p-aminobenzoate (PABANa), and o-aminobenzoate (OABANa), and p-aminobenzoic acid (PABA) on sepiolite, both having a carboxylato functionality (? COO^?) together with an amino (? NH₂) group, were highly reactive with aldehydes. In contrast, PABA which has free carboxylic acid functionality (? COOH: dimeric) was not so reactive with aldehydes. Normal amino acids and their hydrochlorides having ammonio (? NH₂⁺) and ? COO^? or ? COOH (dimeric) groups were less reactive with aldehydes. The reactivity was closely related to the degree of dissociation of carboxylate anion; as the degree of dissociation increases, the compound becomes more reactive. p-Aminobenzoic acid hydrochloride (PABA · HCl), having ? NH₃⁺ and ? COOH (monomeric) groups, was the most reactive (with ethanal) of all the amino acids and their salts examined. Amino acid sodium salts, diamino acid, PABANa, OABANa, and PABA on sepiolite are proved to be excellent removers of aldehydes in ambient air. Among them, PABA · HCl is particularly good for ethanal.     

Polymer‐Supported Lewis Bases for the Baylis–Hillman Reaction

The use of polymer‐supported Lewis bases such as PEG₄₆₀₀‐(PPh₂)₂ and poly(DMAP) in the Baylis–Hillman reactions of N‐tosylimines (ArCHNTs) 1 or the corresponding arenecarbaldehydes with α,β‐unsaturated ketones has been investigated. The corresponding Baylis–Hillman adducts are obtained in good yields. The polymer‐supported Lewis bases can be easily recovered by filtration and the Lewis base PEG₄₆₀₀‐(PPh₂)₂ can be reproduced by reduction with LiAlH₄ and CeCl₃.     

Diazotization–cyanation of aromatic amines with crosslinked poly(4-vinylpyridine)-supported cyanide ions

A simple, mild, and efficient method for the cyanation of stable arenediazonium salts was developed with polymer-supported cyanide. Arenediazonium hydrogen sulfate (Ar N₂⁺HSO₄⁻) was obtained by the reaction between a primary aryl amine and sodium nitrite in the presence of concentrated sulfuric acid (H₂SO₄) at low temperature (0–5°C). By an ion-exchange reaction between Ar N₂⁺HSO₄⁻ and NaBF₄, the stable arenediazonium tetrafluoroborate, Ar N₂⁺BF₄⁻, was prepared. Ar N₂⁺BF₄⁻ was then converted to aryl nitrile with crosslinked poly(4-vinylpyridine) supported cyanide ion in acetonitrile at room temperature. The spent polymeric reagent was regenerated and reused several times without any loss in its activity. This procedure offered advantages, including a higher isolated yield, shorter reaction time, and simple reaction workup. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Linoleate hydroperoxides are cleaved heterolytically into aldehydes by a Lewis acid in aprotic solvent

Treatment of isomeric methyl linoleate hydroperoxides with a Lewis acid, BF₃, in anhydrous ether led to a carbon-to-oxygen rearrangement that caused cleavage into shorter-chain aldehydes. Methyl (9Z,11E)-13-hydroperoxy-9,11-octadecadienoate afforded mainly hexanal and methyl (E)-12-oxo-10-dodecenoate, whereas methyl (10E,12Z)-9-hydroperoxy-10,12-octadecadienoate cleaved into 2-nonenal and methyl 9-oxononanoate. The 2 aldehydes obtained from each hydroperoxide isomer were uncharacteristic of the complex volatile profile usually obtained by β-scission of oxy radicals derived from homolysis of the hydroperoxide group. Rather, the reaction resembled the one catalyzed by the plant enzyme, hydroperoxide lyase. Presented in part at the American Oil Chemists' Society Meeting, Chicago, Illinois, May 8–12, 1983. The mention of firm names or trade products does not imply that they are endorsed or recommended by the USDA over other firms or similar products not mentioned.     

Meerwein's Catalytic Beckmann Rearrangement

Meerwein recommended nitrilium salts ( 2 ) as catalysts for the Beckmann rearrangement of oximes ( 1 ) under neutral and water-free conditions. For the first time, primary adducts (Z)–( 3 ) of oximes to nitrilium salts have been isolated. Reported are activation energies for Beckmann rearrangements of these adducts, and an X-ray structural analysis of (Z)– 3a . Rearrangement of 3 produces mixtures of up to four different N-acylamidinium salts 5 – 8 , which arise from fast reactions of primary-formed secondary amides ( 4 ) with nitrilium salts ( 2 ). Because of their ambident electrophilic character the N-acylamidinium salts react with excess of oxime not only to amides ( 4 ) but to mixtures of products. It is shown that nitrilium salts cannot be used as catalysts for the Beckmann rearrangement.     

Cationic Polymerization Using Heteropolyacid Salt Catalysts

Acid catalysts are used in the production of several commercially important lubricant additives, including dispersants and antioxidants. While the use of conventional mineral and Lewis acids still dominate existing production, heterogeneous solid acid catalysts provide a future option for cost reduction and pollution prevention. The heteropolyacids discussed in this presentation are based on the parent phosphotungstic acid, H₃PW₁₂O₄₀, which has been studied for many years as solid acid catalysts especially by Japanese researchers. A particular class of heterpolyacid salts of the formula (M⁺)_2.5H_0.5PW₁₂O₄₀ exhibit enhanced catalytic activity, which is believed to be due to the formation of a phase with nano-sized crystallites, as has been reported by Misono and coworkers. This class of heteropolyacid salts has been successfully applied by Lubrizol researchers to the production of high-reactivity polyisobutylene, a polymer used in the production of dispersants for commercial lubricants. Most notably, the catalyst of the formula (NH₄ ⁺)_2.5H_0.5PW₁₂O₄₀ provides high conversion to the desired reactive vinylidene isomer and a unique polymer molecular weight distribution, which results in improved performance characteristics when compared to existing commercial AlCl₃ and BF₃ catalysts. Catalyst performance is effectively optimized by catalyst concentration in a slurry reactor, catalyst calcination temperature and loading on a silica support. This class of catalysts has also been successfully applied to a number of other acid-catalyzed processes for the production of additives, including for the antioxidant nonyl diphenylamine.     

Kinetic studies of POSS–DGEBA precursors derived from monoamine functional POSS using dynamic dielectric sensing and nuclear magnetic resonance

Incorporation of pre‐reacted monofunctional polyhedral oligomeric silsesquioxane (POSS)–epoxy adducts dramatically improves dispersion of POSS in epoxy–amine networks. The relationship between reaction kinetics and mechanism for formation of POSS–epoxy adducts versus reaction temperature was investigated. Reactivities of epoxy–monoamine functional POSS molecules were determined using in situ reaction monitoring by dynamic dielectric sensing and ²⁹Si NMR spectroscopy. The amine‐functional POSS–epoxy isothermal reaction showed reduced reactivity due to reduced molecular mobility, that is, diffusion limitations. Kinetic parameters were determined by fitting ²⁹Si NMR data to the model of Kamal that was extended to include diffusion. Fitting of this model to experimental data showed very good agreement over the entire conversion range for pre‐reaction between amine‐functionalized POSS and epoxy. An autocatalytic mechanism, the same as that for the neat epoxy–amine systems, was indicated. Gel permeation chromatography, scanning electron microscopy and transmission electron microscopy were used to investigate molecular weight evolution and morphology of final networks cured by 4,4′ diaminodiphenyl sulfone using pre‐reacted POSS–epoxy adducts. POSS aggregate size decreased with increased pre‐reaction temperature; more homogenous POSS dispersion was observed with higher pre‐reaction temperature. Dynamic mechanical analysis demonstrated that T_g of composites decreased slightly compared to that of the neat matrix and there appeared to be little change in microstructural heterogeneity. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45994.     

The Catalytic Diastereo‐ and Enantioselective Claisen Rearrangement of 2‐Alkoxycarbonyl‐Substituted Allyl Vinyl Ether

The catalytic asymmetric Claisen rearrangement of 2‐alkoxycarbonyl‐substituted allyl vinyl ethers that contain two stereogenic double bonds is described. A combination of the highly Lewis acidic [Cu{(S,S)‐tert‐Bu‐box}](H₂O)₂(SbF₆)₂ complex and molecular sieves served as catalyst and afforded the Claisen rearrangement products, substituted and functionalized α‐keto esters, in high yield with a remarkable diastereo‐ and enantioselectivity. The influence of ligand structure, counterion and allyl vinyl ether double bond configuration on the stereoselectivity of the rearrangement was briefly investigated. We propose an explanation for the rate accelerating effect of the Lewis acid as well as a stereochemical model which serve to explain and predict the stereochemical course of the copper bis(oxazoline) catalyzed Claisen rearrangement.     

Synthesis and characterization of methyl methacrylate/styrene hyperbranched copolymers via living radical mechanism

Free‐radical copolymerizations of N,N‐diethylaminodithiocarbamoylmethylstyrene (inimer: DTCS) with a methyl methacrylate (MMA)/zinc chloride (ZnCl₂) complex were carried out under UV light irradiation. DTCS monomers play an important role in this copolymerization system as an inimer that is capable of initiating living radical polymerization of the vinyl group. The reactivity ratios (r₁ = 0.56 and r₂ = 0.52: DTCS [M₁]; MMA [M₂]) obtained for this copolymerization system were different from a corresponding model system (alternating copolymer) of a styrene and MMA/ZnCl₂ complex (r₁ = 0.25 and r₂ = 0.056). It was found that the hyperbranched copolymers produced exhibited a random branching structure. It was found that the Lewis acid ZnCl₂ formed the complex not only with MMA but also with the carbamate group of inimer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2490–2495, 2003     

Preparation and epoxy curing of novel dicyclopentadiene‐derived Mannich amines

Phenol/dicyclopentadiene (DCPD) adducts were prepared from the BF₃‐catalyzed reaction of p‐nonylphenol and dicyclopentadiene at molar ratios of 2 : 1 and 3 : 2. The phenol‐terminating adducts were consequently reacted with diethylenetriamine and formaldehyde using Mannich reaction conditions. These products containing phenol, amine and tricyclodecane functionalities in the same molecule can be used as epoxy curing agents. The diethylenetriamine was add to the phenol via Mannich reaction at approximately 50% theoretical equivalent. The multiple N H groups in amines and the O H groups in phenols provide crosslinking sites for epoxy resins. The cured epoxy resins show improvement in tensile strength and elongation in comparison with those cured by the poly(oxypropylene) diamine (400 molecular weight) or diethylenetriamine. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2129–2139, 1999