Homogeneous Catalytic Cleavage of Saturated Carbon-Nitrogen Bonds

An evaluation of the catalytic reactivity of [CPD (CO)₂RuH]₂ (1) and (CPD)(CO)₃Ru (2) (where CPD = tetraphenylcyclopentadienone) with amines suggests that these complexes catalyze C-N bond cleavage by activating C-H bonds alpha to the nitrogen atom of tertiary, secondary and primary amines at ca. 140° C. When two different amines are used, transalkylation takes place. With secondary and primary amines, ammonia and tertiary amines are formed. A series of amine complexes (CPD)(CO)₂Ru.NR₃ (R = alkyl/H) was isolated from stoichiometric reactions of 1 or 2 with primary and secondary amines. It was found that tertiary amines do not generate complexes of the above type but rather unexpectedly give secondary amine complexes by cleavage of an alkyl group. The only isolatable tertiary amine complex is the moderately stable (CPD)(CO)₂RuNMe₃. All amine complexes were characterized by spectral and elemental analyses. Catalytic aspects of C-N bond cleavage were studied. Complexes (1) and (2) were found to react with primary, secondary and tertiary amines to generate imminium or eneamine species which subsequently undergo hydrolysis with water. This is in contrast to the Ru carbene mechanism previously proposed for cluster catalyzed C-N bond activation and cleavage. The two reactions are compared with respect to D for H exchange (with D₂O), water requirement and production of trace products during catalysis. A primary alcohol was found to substitute alkyl groups of a tertiary amine under the catalytic action of 1. A catalytic reaction cycle is proposed.     

Isocyanides as Influenza A Virus Subtype H5N1 Wild‐Type M2 Channel Inhibitors

Basic bulky amines such as amantadine are well‐characterized M2 channel blockers, useful for treating influenza. Herein we report our surprising findings that charge‐neutral, bulky isocyanides exhibit activities similar to—or even higher than—that of amantadine. We also demonstrate that these isocyanides have potent growth inhibitory activity against the H5N1 virus. The ?NH₂ to ?N≡C group replacement within current anti‐influenza drugs was found to give compounds with high activities at low‐micromolar concentrations. For example, a tenfold improvement in potency was observed for 1‐isocyanoadamantane ( 27 ), with an EC₅₀ value of 0.487 μm against amantadine‐sensitive H5N1 virus as determined by both MTT and plaque‐reduction assays, without showing cytotoxicity. Furthermore, the isocyanide analogues synthesized in this study did not inhibit the V27A or S31N mutant M2 ion channels, according to electrophysiology experiments, and did not exhibit activity against amantadine‐resistant virus strains.     

Influence of structure of amines on the properties of amines‐modified reduced graphene oxide/polyimide composites

Graphene oxide (GO), as an important precursor of graphene, was functionalized using alkyl‐amines with different structure and then reduced to prepare reduced amines grafted graphene oxide (RAGOs) by N₂H₄ · H₂O. The successful chemical amidation reaction between amine groups of alkyl‐amines and carboxyl groups of GO was confirmed by Fourier transform infrared (FTIR), X‐ray photoelectron spectroscopy (XPS), and thermal gravimetric analysis (TGA). Then RAGOs/polyimide nanocomposites were prepared via in situ polymerization and thermal curing process with different loadings of RAGOs. The modification of amine chains lead to homogenous dispersion of RAGOs in the composites and it formed strong interfacial adhesion between RAGOs and the polymer matrix. The mechanical and electrical properties of polyimide (PI) were significantly improved by incorporation of a small amount of RAGOs, the influence of structure of amines grafted on RAGOs on the enhancement effects of composites was discussed. The research results indicated that the proper structure of amine could effectively enhance the properties of composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43820.     

Reaction of alkyl isocyanides and dialkyl acetylenedicarboxylates in the presence of 5,5-diaryl thiohydantoins. Synthesis of functionalized imidazo[2,1-b][1,3]thiazines

The reaction of stoichiometric amounts of dialkyl acetylenedicarboxylates with alkyl isocyanides in the presence of 5,5-diaryl thiohydantoins afforded imidazo[2,1-b][1,3]thiazines in good overall yields.     

Introduction of quaternary amines onto a film surface by graft polymerization

Quaternary amines were introduced onto a poly(ethylene terephthalate) (PET) film surface by two different methods using UV-induced graft polymerization. The first involves a two-step reaction: graft polymerization of N,N′-(dimethylamino)ethyl methacrylate (DMAEMA) onto the PET film, followed by quaternization of the tertiary N,N′-dimethylamino groups of grafted chains using alkyl bromides (R_nBr). The second is direct graft polymerization of DMAEMA having pendant quaternary amines onto the PET film. The alkyl bromides used for quaternization of the monomers and graft chains include: n-propyl, n-butyl, n-octyl, n-lauryl, and n-cetyl bromide. The two-step method could quaternarize 90% of the pendant N,N′-dimethylamino groups of the graft chains when R₃Br was used. The extent of quaternization decreased with the increasing carbon number of alkyl bromide. The direct one-step method gave a graft amine density of 8 nmol/cm² when the monomer quaternized with R₃Br was used for the graft polymerization in the presence of 1 X 10^-3M sodium metaperiodate. The carbon number of alkyl chains in the quaternary amines estimated from XPS spectra was in good agreement with that of R_nBr used for quaternization. © 1996 John Wiley & Sons, Inc.     

Preparation and characterization of alkylamine-intercalated graphite oxides

Various n-alkylamine-intercalated graphite oxides were synthesized in the presence of a small amount of hexane and their compositions, chemical bonding and orientation of alkyl chains in them were characterized. The interlayer space of graphite oxide was saturated when about 11 mmol/g of n-hexadecylamine was included in it. Three types of alkylamines in GO were identified in the resulting intercalation compounds, hydrogen-bonded neutral amines, hydrogen-bonded protonated amines and ionically bound protonated amines, based on the infrared and XPS studies. The equilibrium between these species was established. Immersion of GO saturated by n-hexadecylamine in ethanol resulted in the de-intercalation of amines and the amount of residual amines was 3.0 mmol/g, which was rather similar to that of readily exchangeable protons in GO of 3.5 mmol/g. When alkyl chain length became shorter, the resulting intercalation compounds contained less alkylamine due to insufficient hydrophobic interaction between alkyl chains. The X-ray diffraction and polarized-infrared spectroscopic data indicated that alkyl chains of alkylamines took interdigitated monolayer and bilayer orientations for smaller and larger interlayer spacings, respectively.     

Organo-catalytic synthesis of oxathians from isocyanides,isothiocyanates, and oxiranes

ABSTRACT

A novel three-component reaction between isocyanides, isothiocyanates, and oxiranes has been developed. An array of substituted oxathianes have been obtained in acceptable to good yields. The reaction product could be modulated using Bu₃P or TBPAc as an organo-catalyst. This work offers an opportunity for the further implementation of isocyanides in library design.     

Gas-liquid chromatography of fatty derivatives

Summary The separation of fatty amines has been carried out with nonpolar substrates on solid supports of Chromosorb and Chromosorb W, which were previously treated with potassium hydroxide to overcome adsorptivity. In this manner well-resolved symmetrical peaks are obtained. Untreated supports give peaks which trail and prohibit precise quantitative measurements. Both Apiezon L on Chromosorb W and Silicone Grease on Chromosorb have proved effective, the latter at 176°C. and the former at 225°C. Relative detector sensitivity factors have been determined for the amines C₈ to C₁₈, thus permitting accurate analyses. The relative response for primary alkyl fatty amines is a linear function of molecular weight. The application of gas chromatography described in this paper was conceived and developed independently and simultaneously in the respective research laboratories of these two companies.     

Synthesis and evaluation of micellar properties and antimicrobial activities of imidazole‐based surfactants

The synthesis of two types of imidazole‐based surfactants, [(ROCOCH₂MIm)Br] and [(RNHCOCH₂MIm)Br], of varying chain lengths (C₁₀, C₁₂ and C₁₆), was conducted in the present work. The synthesis involves an initial reaction of bromoacetic acid with fatty alcohols or fatty amines, followed by quaternization with N‐methyl imidazole. The micellar properties of all the synthesized compounds were determined using surface tensiometry and compared with [(RMIm)Br], a well‐studied alkyl‐substituted imidazole‐based surfactant. Within the same homologous series, a decrease in critical micelle concentration (cmc) was observed with increasing alkyl chain length in all three types of cationic surfactants. Introduction of an ester [(ROCOCH₂MIm)Br] or an amide group [(RNHCOCH₂MIm)Br] in the alkyl chain lowers the cmc when compared to a cationic surfactant without functional group, [(RMIm)Br]. The synthesized surfactants were also assayed for antimicrobial activities and found to possess good activities against selected strains.     

Grafting PEG and alkyl comb polymers onto bleached wood pulp fibres

Comb polymers were prepared by reacting a poly(ethylene-alt-maleic anhydride) with alkyl amines or poly(ethylene glycol) (PEG) amines. The resulting polymers were used to modify bleached softwood kraft pulp fibre surfaces by catalyst-free grafting in a process suitable for pulp mill implementation. Pulp fibres were impregnated with a polymer solution and cured above 100°C. High grafting yields were obtained despite having up to 88% of the anhydride groups consumed by amine derivatization. Grafting yields were more than 90% when the polymer dosage was <13 g/kg (dry polymer/dry fibre) for alkyl derivatives and < 38 g/kg for PEG derivatives. We propose that the upper dosage limit for efficient grafting reflects the need for direct contact between cellulose and every polymer chain for ester linkage formation. For a given polymer dosage, the cured pulp sheets had a maximum wet tensile index, TI_max, when either curing time or temperature was increased. Both the alkyl and PEG derivatives fit the power law for the wet TI_max~βΓ_ru^0.54–0.62 where β values were the estimated conversion of succinic acid moieties to anhydrides when the pulp sheets were cured, and Γ_ru is the dimensionless polymer content that is numerically equal to the amount of applied polymer in mmol repeat units/g dry fibre. However, high polymer dosages give experimental TI_max values that fall below the power law, irrespective of curing intensity, because the pulp sheets contain unfixed polymer chains that lubricate fibre/fibre joints, lowering wet strength.     

Description of the thermodynamic properties and fluid-phase behavior of aqueous solutions of linear,branched, and cyclic amines

The SAFT-γ Mie group-contribution equation of state is used to represent the fluid-phase behavior of aqueous solutions of a variety of linear, branched, and cyclic amines. New group interactions are developed in order to model the mixtures of interest, including the like and unlike interactions between alkyl primary, secondary, and tertiary amine groups (NH₂, NH, N), cyclic secondary and tertiary amine groups (cNH, cN), and cyclic methine-amine groups (cCHNH, cCHN) with water (H₂O). The group-interaction parameters are estimated from appropriate experimental thermodynamic data for pure amines and selected mixtures. By taking advantage of the group-contribution nature of the method, one can describe the fluid-phase behavior of mixtures of molecules comprising those groups over broad ranges of temperature, pressure, and composition. A number of aqueous solutions of amines are studied including linear, branched aliphatic, and cyclic amines. Liquid–liquid equilibria (LLE) bounded by lower critical solution temperatures (LCSTs) have been reported experimentally and are reproduced here with the SAFT-γ Mie approach. The main feature of the approach is the ability not only to represent accurately the experimental data employed in the parameter estimation, but also to predict the vapor–liquid, liquid–liquid, and vapor–liquid–liquid equilibria, and LCSTs with the same set of parameters. Pure compound and binary phase diagrams of diverse types of amines and their aqueous solutions are assessed in order to demonstrate the main features of the thermodynamic and fluid-phase behavior.     

A comparative kinetics study of CO2 absorption into aqueous DEEA/MEA and DMEA/MEA blended solutions

The kinetics of CO₂ absorption into aqueous solutions of N,N‐diethylethanolamine (DEEA), and N,N‐dimethylethanolamine (DMEA), and their blends with monoethanolamine (MEA) have been studied in a stopped‐flow apparatus. The kinetics experiments were carried out at the concentrations of DEEA and DMEA varying from 0.075 to 0.175 kmol/m³, respectively, and that of MEA ranging between 0.0075 and 0.0175 kmol/m³, over the temperature range of 293–313 K. Two kinetics models are proposed to interpret the reaction in the blended amine systems and the results show that the model which incorporates the base‐catalyzed hydration mechanism and termolecular mechanism resulted in a better prediction. Furthermore, the kinetics behaviors of CO₂ absorption into two blended systems are comprehensively discussed according to their molecular structures. It can be concluded that the interaction between tertiary amines and primary amines as well as the alkyl chain length of tertiary amines have a significant influence on the kinetics. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1350–1358, 2018     

Untersuchungen zur intramolekularen C?C-Verknüpfung von Dienen durch Basenkatalyse. III. [1] Cyclisierung von Diallylaminen

Attempts to Intramolecular C C-Connexions of Dienes by Base-catalysis. III. Cyclization of Diallyl Amines Diallyl alkyl amines 1 are isomerized to the corresponding dipropenyl alkyl amines with potassium on alumina catalyst. The trans, trans-isomers are thermodynamically prefered. If the alkyl group in the diallyl alkyl amines is replaced by an electron-attracting group a cyclization to tetrahydropyridines takes place. The base-catalysed isomerization of diallyl ether 3 does not give a cyclic product. Diallyl sulfide 4 can be isomerized to 5-methyl thiacyclohexen-(2) 4a .     

Control of ionic interactions in sulfonated polystyrene ionomers by the use of alkyl-substituted ammonium counterions

Polystyrenes containing up to about 20 mol % sulfonic acid are reproducibly and readily prepared by the sulfonation of polystyrene at 50°C with acetyl sulfate in 1,2-dichloroethane solution. The metal salts of sulfonated polystyrene possess extremely high melt viscosities and are soluble in single solvents such as toluene and THF only at very low sulfonate levels. Such properties are the result of the very strong ion-dipole interactions among the metal sulfonate groups. Such strong interactions can be substantially reduced through the neutralization of the sulfonic acid with ammonia and, most especially, relatively simple low molecular weight amines. Sulfonated polystyrenes varying in sulfonic acid content from about 1 mol % to about 20 mol % were neutralized with various mono-, di-, and tri-substituted alkyl amines ranging in alkyl chain length from H (ammonia) to C₂₀, and their rheological and thermal properties were measured. As the number of substituents on the nitrogen increased, the glass transition temperature and the melt viscosity decreased. The tributylamine sulfonates possessed viscosities almost as low as unsulfonated polystyrene and the longer chain amines behaved as if internally plasticized. The properties of amine neutralized sulfonated polystyrenes are concluded to be primarily a function of amine size. Increasing the size of the amine reduces the strength of the ion-dipole interaction by preventing close approach of the amine sulfonate groups.     

1,2,5, 6‐Tetrazocines from Nitrile Imines and tert‐Butyl Isocyanide

tert‐Butyl isocyanide ( 2 ) reacts with acceptor‐substituted nitrile imines to give derivatives of tetrahydro‐1,2,5,6‐tetrazocines 3 along with substituted 5‐hydrazonoyl‐1,2,4‐triazoles 4 . Replacement of 2 with aryl or sec‐alkyl isocyanides leads to substituted a‐hydrazonoamides ( 6B ) rather than to analogues of 3 ; removal of the acceptor group in 1 is likewise detrimental. — The structure of 3 has been established by means of an X‐ray diffraction analysis of 3d .     

Investigations into the mechanism of the liquid-phase hydrogenation of nitriles over Raney-Co catalysts

The co-hydrogenation of acetonitrile and butyronitrile over Raney-Co was investigated in order to obtain insight into the mechanism underlying the formation of secondary amines. Acetonitrile was reduced much faster to the corresponding primary amine due to stronger adsorption on the catalyst surface. In parallel, dialkylimines were formed and subsequently converted to secondary amines. It is suggested that the dialkylimines are formed by reaction of partially hydrogenated intermediate species on the cobalt surface with amines. In this respect, n-butylamine was found to react much faster than ethylamine. The stronger inductive effect of the butyl chain is thought to facilitate nucleophilic attack of the amine at the α-C-atom of the surface species. By comparing the C₂ and C₄ balance for dialkylimines and dialkylamines, it was found that direct hydrogenation of the dialkylimine cannot be the only way of dialkylamine formation. Instead, it is suggested that alkyl group transfer occurs by reaction of a monoalkylamine with a dialkylimine and cross-transfer between two dialkylimines.     

Catalytic activation of hydrazine hydrate by gold nanoparticles: Chemoselective reduction of nitro compounds into amines

Supported gold nanoparticles (< 1 mol%) catalyze for the first time the activation of NH₂NH₂ as a transfer hydrogenation agent. Aryl and alkyl nitro compounds are cleanly and selectively reduced into the corresponding amines in the presence of 4 equivalents of hydrazine. The reaction tolerates other potentially reducible functionalities such as carboxylate, carbonyl, cyano or halides which remain intact.     

SOLVENT EXTRACTION OF GOLD IN THIOSULFATE SOLUTIONS WITH AMINES

ABSTRACT

The solvent extraction of gold from thiosulfate solutions with alkyl amines was studied. The experimental results showed that with both aliphatic and aromatic hydrocarbons as diluent, the power of amines for extraction of gold decreased in the order: primary > secondary > tertiary amine. Further study indicated that the initial gold concentration and ionic strength in aqueous phase had no significant influence on the extraction of gold with primary amine N₁₉₂₃. The extraction of gold at high pH values increased with an increase of the extractant concentration. The enthalpy change for the extraction with N₁₉₂₃ was calculated ?120.8 kJ mol^?1. From these experimental results, the equations of extraction of gold with N₁₉₂₃ from thiosulfate solution with and without the presence of ammonia have been derived respectively.     

Mono- and diquaternary ammonium cellulose cottons prepared in nonaqueous media

Mono- and diquaternary ammonium cellulose anion exchangers in fabric form were prepared in nonaqueous media by reacting diethylaminoethyl (DEAE)-cotton with an alkyl halide, RX, or a dihaloalkane, X(CH₂)_nX, respectively. The alkyl group was varied from CH₃ to C₁₈H₃₅, and n varied from 5 to 10 in the dihaloalkanes. Electron emission spectroscopy for chemical analyses (ESCA) showed that approximately 70% of the amino groups in the original DEAE-cotton were free amines. ESCA data showed that highest degree of quaternization of the free amine groups was obtained with CH₃I but that diiodo and dibromo pentanes and decanes were also effective. Diquaternary ammonium cellulose exchangers of high nitrogen content had high wet and conditioned wrinkle recoveries, whereas the monoquaternary ammonium cellulose exchangers showed no improvement in wet or conditioned wrinkle recoveries. The monoquaternaries, like unmodified cottons and DEAE-cottons, were soluble in cupriethylenediamine hydroxide (cuene), and cross sections of their fibers expanded when subjected to layer expansion techniques. All diquaternaries were insoluble in cuene, and their cross sections did not layer.     

GOLD EXTRACTION FROM THIOSULFATE SOLUTIONS USING MIXED AMINES

ABSTRACT

The extraction of gold from thiosulfate solutions with amine oxide and its mixture with amines has been studied, the results show that the amine oxide (TRAO) has a higher extraction ability for gold compared with tertiary amine. It can extract gold from neutral and weakly alkaline thiosulfate solutions, similar to the primary amine as extractant. The addition of TRAO enhances the extent of gold extraction with primary, secondary, and tertiary alkyl amines, respectively. The stoichiometry for the extraction of gold from thiosulfate solutions using the mixed solvent containing the primary amine N₁₉₂₃ and the amine oxide TRAO was investigated using slope analysis. The compositions of the gold extraction species with mixed organic solvents are proposed.