Electrooxidation-Induced Multicomponent Cascade Cyclization via Selective Cleavage of Tertiary Amine C-N Bond.

Nitriles were found to be highly effective alkylating reagents for the selective N-alkylation of amines under catalytic hydrogenation conditions. For the aromatic primary amines, the corresponding secondary amines were selectively obtained under Pd/C-catalyzed hydrogenation conditions. Although the use of electron poor aromatic amines or bulky nitriles showed a lower reactivity toward the reductive alkylation, the addition of NH(4)OAc enhanced the reactivity to give secondary aromatic amines in good to excellent yields. Under the same reaction conditions, aromatic nitro compounds instead of the aromatic primary amines could be directly transformed into secondary amines via a domino reaction involving the one-pot hydrogenation of the nitro group and the reductive alkylation of the amines. While aliphatic amines were effectively converted to the corresponding tertiary amines under Pd/C-catalyzed conditions, Rh/C was a highly effective catalyst for the N-monoalkylation of aliphatic primary amines without over-alkylation to the tertiary amines. Furthermore, the combination of the Rh/C-catalyzed N-monoalkylation of the aliphatic primary amines and additional Pd/C-catalyzed alkylation of the resulting secondary aliphatic amines could selectively prepare aliphatic tertiary amines possessing three different alkyl groups. According to the mechanistic studies, it seems reasonable to conclude that nitriles were reduced to aldimines before the nucleophilic attack of the amine during the first step of the reaction.

The preparation of PVC compounds bearing primary aliphatic and/or aromatic amine groups exhibit several challenges which have been faced in this work. On the one hand, this polymer has never before been modified with aliphatic amine groups in a controlled manner or with a tailored degree of substitution. In this work we present a way to obtain, for the first time in a very selective way and with high degrees of substitution, PVC bearing aliphatic primary amine groups by chemical modification of the polymer. The modifier used for this purpose is 4-aminomethylthiophenol that has been synthesized starting from inexpensive benzyl chloride that is reacted with potassium phthalimide yielding a protected amine functionality. The aromatic thiol functionality, required for the introduction of the modifier molecule by nucleophilic substitution of PVC chlorine atoms is achieved by chlorosulfonation in para-position of the aromatic ring and reduction of the chlorosulfonyl group using sodium borhydride. This compound is used to modify PVC bearing a protected primary amine. The free amine is obtained after deprotection of the phthalimide moiety using hydrazine. On the other hand, the synthesis of primary aromatic amines has been described in the past using expensive precursors. In this work, 2-aminothiophenol or 3-aminothiophenol are used in order to modify the polymer with primary aromatic amine groups using inexpensive starting material.

Selective recognition of ammonia and aliphatic amines by C-N fused phenazine derivative: A hydrogel based smartphone assisted ‘opto-electronic nose’ for food spoilage evaluation with potent anti-counterfeiting activity and a potential prostate cancer biomarker sensor

Synergistic CO2 Mediation and Photocatalysis for α-Alkylation of Primary Aliphatic Amines

Selective spectrophotometric determination of some primary amines using 2,4-dinitrofluorobenzene reagent

We previously reported the novel efficient proton/heat-promoted four-component reactions (4CRs) of but-2-ynedioates, two same/different primary amines, and aldehydes for the synthesis of tetra- and pentasubstituted polyfunctional dihydropyrroles. If aromatic and aliphatic amines were used as reagents, four different series of products should be obtained via the permutation and combination of aromatic and aliphatic primary amines. However, only three/two rather four different series of tetra-/pentasubstisuted dihydropyrroles could be prepared via the proton/heat-promoted 4CRs. Herein, Cu(OAc)2·H2O, a Lewis acid being stable in air and water, was found to be an efficient catalyst for the 4CR synthesis of all the four different series of tetra-/pentasubstisuted dihydropyrroles. The copper-catalyzed 4CR could produce target products at room temperature in good to excellent yields. Interestingly, benzaldehyde, in addition to being used as a useful reactant for the synthesis of pentasubstituted dihydropyrroles, was found to be an excellent additive for preventing the oxidation of aromatic amines with copper(II) and ensuring the sooth conduct of the 4CRs for the synthesis of tetrasubstituted dihydropyrroles with aryl R(3). In addition, salicylic acid was found to be needed to increase the activities and yields of the copper-catalyzed 4CRs for the synthesis of petasubstituted diyhydropyrroles. On the basis of experimental results, the enamination/amidation/intramolecular cyclization mechanism was proposed and amidation is expected to be the rate-limited step in the copper-catalyzed 4CRs.

Reactions of N-polyfluorophenylcarbonimidoyl dichlorides with primary and secondary amines. Kinetics and mechanism. Synthesis of polyfluorinated carbodiimides, chloroformamidines, guamidines and benzimidazoles.

Selective separation of aliphatic tertiary amines and aromatic amines by using CO2

Selective cleavage of Csp3–N bonds in aliphatic tertiary amines enabled by difluorocarbene to access esters and thioethers

In many practical processes, separation of aliphatic amines from aromatic amines in water is imperative to obtain the desired products. In this work, a novel strategy was proposed for selective separation of aliphatic amines from aromatic amines with CO2 switchable ionic liquids (ILs) aqueous two-phase systems (ATPSs). It was shown that upon introduction of CO2 into an aqueous solution containing the IL, aliphatic amine and aromatic amine at 25 °C and atmospheric pressure, an ATPS could be formed with an IL-rich top phase and an ammonium-salt-rich bottom phase. Under these circumstances, the aromatic amine was largely partitioned in the IL-rich phase, while the aliphatic amine was transformed into the ammonium salt by the reaction with CO2. Thus the aliphatic amine was well separated from the aromatic amine in aqueous solution. The distribution ratios of aromatic amines between the two phases were found to increase with increasing hydrophobicity of ILs and aromatic amines, pKa values of aliphatic amines and tie-line length of the systems. Moreover, aliphatic amines retained in the ammonium-salt-rich phases were regenerated by bubbling N2 under heating, while aromatic amines in the IL-rich phases were removed by simple steam distillation. The recovery efficiency for aliphatic amines was as high as 99.0%. The regenerated ILs could then be reused in the next separation process, and no decrease in the distribution ratios of aromatic amines was observed after six cycles.

The reduction of CO2 (1 atm) with 9-BBN in DMSO in the presence of amines at 90 °C selectively gave N-formamides in good to excellent yields. This method works with a range of substrates, including heterocyclic secondary amines and primary and secondary aliphatic and aromatic amines. Remarkably, the same CO2 (1 atm) reduction in the presence of a catalytic amount of DMSO and aromatic primary and secondary amines in toluene at room temperature afforded N-methylamine products isolated in 44-97% yields, representing the first room temperature method using hydroborane. Interestingly, the reduction of CO2 (1 atm) in the presence of carbazole and indole derivatives gave the N-hydroxymethylated products in good to excellent yields, representing the hitherto unknown direct conversion of CO2 under mild conditions. More interestingly, the addition of indole or N-methylindole to the reaction mixture containing the hydroxymethylated products at 60 °C resulted in the formation of new C-N-coupled products. The proposed mechanism, based on several control experiments, suggests that the transfer of a formyl group from the formoxyborane occurs, which then leads to the N-methylation after reduction with 9-BBN. Another possible route is the nucleophilic attack of formoxy- or methoxyborane on the aminoborane formed in the reaction mixture.

Chromaticity sensor for discriminatory identification of aliphatic and aromatic primary amines based on conformational changes of polyacetylene

Reactions of 4-substituted 5 H-1,2,3-dithiazoles with primary and secondary amines: fast and convenient synthesis of 1,2,5-thiadiazoles, 2-iminothioacetamides and 2-oxoacetamides

A simple colorimetric method for the determination of vaporous aliphatic amines has been developed. Importantly, the recognition of vaporous aliphatic amines could be observed by naked eyes owing to color change of the synthesized azobenzothiazole-polyene dye from orange to dark blue in the solution. The results revealed that primary amines can form 1:2 and secondary amines 1:1 complexes with the dye, respectively. The sensing of this chemosensor is capable over a dynamic linear ranges between $10^{\mathrm {-2}}$ – $10^{\mathrm {-6}}\text{M}$ for primary aliphatic amines and $10^{\mathrm {-2}}$ – $10^{\mathrm {\mathbf {-4}}}\text{M}$ for secondary aliphatic amines. The response of the dye to tertiary amines or aromatic amines was not strong enough to make a strong color change. Validation of the assay method revealed excellent performance characteristics, including high repeatability and highly recognizable color change.

Most polymer-polymer pairs are immiscible. However, if one polymer is properly dispersed within another, unique morphologies can be created with synergistic properties.1 For example, sheets of a low permeability polymer can greatly increase the barrier performance of a layered composite,2 while submicron size droplets of a rubbery phase can improve toughness 10-fold3 in a glassy or semicrystalline plastic. The key to these property improvements is creation and stabilization of the desired composite morphology. Intensive mixing as the polymers melt can create thin sheets, and subsequently fine droplets,4 of the minor component. However, these small droplets rapidly coalesce since they are far from thermodynamic equilibrium.4,5 The most successful strategy for stabilizing or compatibilizing these nonequilibrium structures is to fix complementary functional groups on the two polymers that can couple at the interfaces forming a graft or block copolymer during mixing.6 This copolymer provides a physical barrier against coalescence5,7-10 and also increases adhesion between the two phases, improving mechanical properties.11,12 In most previous studies and commercial processes graft or cross-linked copolymers were produced.6 Such branched and network structures tend to inhibit interfacial deformation, thereby restricting further area generation. We have prepared polymer chains with a single functional group on just one end. These terminally functional polymers can only form diblock copolymers. With a moderate chemical reactivity these functional groups produce relatively fine, stable droplets7 similar to results with reactively formed graft or crosslinked copolymers.3,5,6,9,13 However, we have recently discovered that very fast reaction rates lead to coupling of all the reactive chains when the mixture is shear processed. The resulting block copolymer self-assembles into a nanostructured morphology. Three different types of heterogeneous blends were studied in our experiments, each prepared with 70 wt % polystyrene (I) and 30 wt % of polyisoprene (II) (or polybutadiene). The first set of blends did not contain functional groups, while the second set involved a cyclic anhydride (III) attached to the polydiene,14 reacting with a primary aromatic amine (IV) at the terminus of the polystyrene.15 For the third set a primary aliphatic amine (V) was substituted for the aromatic amine of the second mixture.16 The blends were prepared by shear mixing in the molten state.17 The polydiene minor phase is expected to break up into droplets.4,5 Conversion of the reaction was determined by gel permeation chromatography (GPC) using a UV detector sensitive only to the polystyrene as it eluted from the columns. Since the polymers were relatively monodisperse,18 the amount of coupled chains could easily be distinguished and quantified.7 Phenyl isocyanate was added to the samples before dissolving in THF to quench all remaining amino groups. This prevented further reaction in solution and prevented adsorption of the amino groups to the chromatographic columns. At high temperatures a primary amine reacts essentially irreversibly with a cyclic anhydride to produce a cyclic imide plus water.19 The reaction of the aromatic amine with cyclic anhydride is relatively slow, while the reaction of the aliphatic amine is extremely fast compared to the blending process time scale. Comparative rates of reaction were measured by preparing homogeneous blends of reactive polystyrene containing the complementary functional groups in a stoichiometric ratio. The aromatic amine reaction reached a maximum conversion of 36% at 180 °C over the 20 min mixing time employed in these experiments. The aliphatic amine reaction reached essentially complete conversion to coupled chains in less than 1 min, i.e., when the first sample was removed from the mixer (see Figure 1a). Approximate rates of generation of block copolymer can be determined from the data in Figure 1a using the initial slopes. For the aromatic amine reaction we get