Simple Amines Research Articles

Simple Amine-Directed Meta-Selective C-H Arylation via Pd/Norbornene Catalysis.

Herein we report a highly meta-selective C-H arylation using simple tertiary amines as the directing group. This method takes advantage of Pd/norbornene catalysis, offering a distinct strategy to control the site selectivity. The reaction was promoted by commercially available AsPh3 as the ligand and a unique "acetate cocktail". Aryl iodides with an ortho electron-withdrawing group were employed as the coupling partner. A wide range of functional groups, including some heteroarenes, are tolerated under the reaction conditions. In addition, the amine directing group can be easily installed and transformed to other common versatile functional groups. We expect this C-H functionalization mode to have broad implications for developing other meta-selective transformations beyond this work.

From Isonitriles to Unsaturated NHC Complexes of Gold, Palladium and Platinum

AbstractIn a modular template synthesis, unsaturated NHC complexes of gold, palladium and platinum were synthesized from simple metal salts, isonitriles and amines with acetal or ketal groups. Upon the addition of amines with tethered acetal or ketal moieties to the metal‐activated isonitrile, first nitrogen acyclic carbene (NAC) complexes are formed. These undergo ring closure and elimination to the unsaturated NHC complexes upon addition of acid. This simple strategy opens an attractive and fast approach to NHC complexes of gold, palladium and platinum. The modular approach allows a fast modification and is well‐suited for the synthesis of unsymetrically and symmetrically substituted unsaturated NHC complexes.magnified image

Surface modification of Cu flakes through Ag precipitation for low-temperature pressureless sintering bonding

Cu flakes with surface modified by precipitated Ag nanoparticles (NPs) were investigated for potential use as a sinter joining material. The surface modification was conducted via a simple and green amine treatment process. The precipitated Ag inter-NPs improved the sintering ability of the Cu flakes by increased necking and grain growth at 250°C. The linked Ag network formed a dense microstructure of the sinter joining layer and contributed to the Cu flake connection. The surface-modified Cu flakes exhibit 30% less oxidation than the original flakes at temperatures as high as 200°C. The present surface modification expands the application of Cu flake paste to sinter joining for heat-resistant interconnections.

Michael Addition Initiated Substrate- or Catalyst-Controlled Chemodivergent Three-Component Construction of Fused and Bridged Polycyclic Heterocycles

The results on the multicomponent reaction between cyclic β-keto esters, enals, and simple primary aliphatic amines are reported. In thermal conditions in the presence of 4 Å molecular sieves, two different­ families of heterocyclic products (aminobicyclo[3.3.1]nonanones or cycloalka[<i>b</i>]piperidines) were obtained depending on the presence of a substituent in the α-position of the aldehyde. Moreover, preliminary results on the possibility to obtain these two bicyclic cores from the very same starting materials by introducing organocatalysts with different activation modes in the reaction are presented.

Localized template-driven functionalization of nanoparticles by dynamic combinatorial chemistry.

We have developed a method for the localized functionalization of gold nanoparticles using imine-based dynamic combinatorial chemistry. By using DNA templates, amines were grafted on the aldehyde-functionalized nanoparticles only if and where the nanoparticles interacted with the template molecules. Functionalization of the nanoparticles was controlled solely by the DNA template; only amines capable of interacting with DNA were bound to the surface. Interestingly, even though our libraries contained only a handful of simple amines, the DNA sequence influenced their attachment to the surface. Our method opens up new opportunities for the synthesis of multivalent, nanoparticle-based receptors for biomacromolecules.

Localized Template‐Driven Functionalization of Nanoparticles by Dynamic Combinatorial Chemistry

AbstractWe have developed a method for the localized functionalization of gold nanoparticles using imine‐based dynamic combinatorial chemistry. By using DNA templates, amines were grafted on the aldehyde‐functionalized nanoparticles only if and where the nanoparticles interacted with the template molecules. Functionalization of the nanoparticles was controlled solely by the DNA template; only amines capable of interacting with DNA were bound to the surface. Interestingly, even though our libraries contained only a handful of simple amines, the DNA sequence influenced their attachment to the surface. Our method opens up new opportunities for the synthesis of multivalent, nanoparticle‐based receptors for biomacromolecules.

Simple primary amine catalyzed aerobic reductive ring-cleavage of isoxazole motif

A clean and highly efficient catalytic aerobic reductive ring-cleavage of 3–methylanthra[1,2-c]isoxazole-6,11-dione to 1-amino-2-acetylanthraquinone was performed using simple organic amines as organocatalysts and water as a green reaction medium. This method provides a new clean transformation of isoxazole-containing compounds to the corresponding ortho-amino ketones. The catalytic performance of various organic amines was carefully screened, and simple organic primary amines were found to be promising practical catalysts with outstanding catalytic performance. Isopropylamine as the organocatalyst gave 97.2% conversion of 3–methylanthra[1,2-c]isoxazole-6,11-dione, with 97.2% selectivity to 1-amino-2–acetylanthraquinone, in the presence of oxygen only, using 1 equiv. of hydrazine hydrate at room temperature for 3 h. A possible mechanism is also proposed.

Stimuli responsive reversible high contrast off–on fluorescence switching of simple aryl-ether amine based aggregation-induced enhanced emission materials

Aryl-ether amine based simple Schiff base molecules showed rare stimuli responsive off–on fluorescence switching with high contrast.

Diastereoselective synthesis of substituted diaziridines from simple ketones and aldehydes.

Diastereopure substituted diaziridines from simple ketones, aldehydes and amines are here reported. These important chemical scaffolds are obtained in the presence of a weak inorganic base and hydroxylamine O-sulfonic acid (HOSA). This method introduces three stereocenters in one step to provide a wide variety of substituted diaziridines with high yields and diastereoselectivities.

Oxime formation from hydroxylamine and ketone: a (computational) reality check on stage one of the mechanism.

Oxime formation from hydroxylamine and ketone: a (computational) reality check on stage one of the mechanism.

Amines functionalized C60 as solid base catalysts for Knoevenagel condensation with high activity and stability

Amines functionalized C60 were prepared through a simple amination reaction of C60 with organic amines, and they showed high activity and stability for Knoevenagel condensation.

Optimization of selection of chain amine scrubbers for CO2 capture

In order to optimize the selection of a suitable amine molecule for CO2 scrubbers, a series of ab initio calculations were performed at the B3LYP/6-31+G(d,p) level of theory. Diethylenetriamine was used as a simple chain amine. Methyl and hydroxyl groups served as examples of electron donors, and electron withdrawing groups like trifluoromethyl and nitro substituents were also evaluated. Interaction distances and binding energies were employed as comparison operators. Moreover, natural bond orbital (NBO) analysis, namely the second order perturbation approach, was applied to determine whether the amine-CO2 interaction is chemical or physical. Different sizes of substituents affect the capture ability of diethylenetriamine. For instance, trifluoromethyl shields the nitrogen atom to which it attaches from the interaction with CO2. The results presented here provide a means of optimizing the choice of amine molecules for developing new amine scrubbers.

Iron catalysed direct alkylation of amines with alcohols.

The selective conversion of carbon-oxygen bonds into carbon-nitrogen bonds to form amines is one of the most important chemical transformations for the production of bulk and fine chemicals and pharma intermediates. An attractive atom-economic way of carrying out such C-N bond formations is the direct N-alkylation of simple amines with alcohols by the borrowing hydrogen strategy. Recently, transition metal complexes based on precious metals have emerged as suitable catalysts for this transformation; however, the crucial change towards the use of abundant, inexpensive and environmentally friendly metals, in particular iron, has not yet been accomplished. Here we describe the homogeneous, iron-catalysed, direct alkylation of amines with alcohols. The scope of this new methodology includes the monoalkylation of anilines and benzyl amines with a wide range of alcohols, and the use of diols in the formation of five, six- and seven- membered nitrogen heterocycles, which are privileged structures in numerous pharmaceuticals.

Sustainable synthesis of thioimidazoles via carbohydrate-based multicomponent reactions.

The synthesis of diversely functionalized thioimidazoles through a modern variant of the Marckwald reaction is presented. This new protocol utilizes unprotected carbohydrates as well as simple amine salts as sustainable and biorenewable starting materials. Importantly it was discovered that a bifurcated reaction pathway results from using aldoses and ketoses respectively, yielding distinct reaction products in a highly selective manner.

Asymmetric enamine catalysis with β-ketoesters by chiral primary amine: divergent stereocontrol modes.

α-Branched ketones remain a challenging type of substrates in aminocatalysis due to their congested structures as well as the associated difficulties in controlling chemo- and stereoselectivity. In this work, we have explored asymmetric aminocatalysis with α-substituted β-ketoesters. A simple chiral primary amine catalyst was identified to enable unprecedentedly effective catalysis of β-ketoesters in α-hydrazination and Robinson annulation reaction with good yields and high enantioselectivities. Stoichiometric experiments with preformed enamine ester intermediates revealed their enamine-catalytic nature as well as the critical roles of acidic additives in facilitating catalytic turnovers and in tuning the chemo- and stereoselectivity. With the identical catalytic system, the two reactions demonstrated opposite chiral inductions in terms of the absolute configurations of the newly formed stereogenic centers. Investigations into this intriguing issue by DFT have revealed divergent stereocontrol modes. For α-hydrazination, H-bonding-directed facial attack determines the stereoselectivity, whereas a steric model is applied to the Robinson annulation where dual activations of both β-ketoester and vinyl ketone/aldehyde are involved.

Formation of Air Stable Graphene p–n–p Junctions Using an Amine‐Containing Polymer Coating

An ultrathin layer of a polymer containing simple aliphatic amine groups, polyethylenimine ethoxylated (PEIE), is deposited on a back‐gated field effect graphene device to form graphene p–n–p junctions. Characteristic I–V curves indicate the superposition of two separate Dirac points, which confirms an energy separation of neutrality points within the complementary regions. This is a simple approach for making graphene p–n–p junctions without a need for multiple lithography steps or electrostatic gates and, unlike, the destructive techniques such as substitutional doping or covalent functionalization, it induces a minor defect, if any, as there is no discernible D peak in the Raman spectra of the graphene films after creating junctions and degradation in the charge carrier mobilities of the graphene devices. This method can be easily processed from dilute solutions in environmentally‐friendly solvents such as water or methoxyethanol and does not suffer any change upon exposure to air or heating at temperatures below 100 °C.

Dynamic CO2 adsorption performance of internally cooled silica‐supported poly(ethylenimine) hollow fiber sorbents

The dynamic adsorption behavior of CO2 under both nonisothermal and nearly isothermal conditions in silica supported poly(ethylenimine) (PEI) hollow fiber sorbents (Torlon®‐S‐PEI) is investigated in a rapid temperature swing adsorption (RTSA) process. A maximum CO2 breakthrough capacity of 1.33 mmol/g‐fiber (2.66 mmol/g‐silica) is observed when the fibers are actively cooled by flowing cooling water in the fiber bores. Under dry CO2 adsorption conditions, heat released from the CO2‐amine interaction increases the CO2 breakthrough capacity by reducing the severity of the diffusion resistance in the supported PEI. This internal resistance can also be alleviated by prehydrating the fiber sorbent with a humid N2 feed. The CO2 breakthrough capacity of prehydrated fibers is adversely affected by the release of the adsorption enthalpy (unlike the dry fibers); however, active cooling of the fiber results in a constant CO2 breakthrough capacity even at high CO2 delivery rates (i.e., high adsorption enthalpy delivery rates). In full RTSA cycles, a purity of 50% CO2 is achieved and the adsorption enthalpy recovery rate can reach ∼72%. Studies on the cyclic stability of uncooled fiber sorbents in the presence of SO2 and NO contaminants indicate that exposure to NO at 200 ppm over 120 cycles does not lead to a significant degradation of the sorbents, but SO2 exposure at a similar high concentration of 200 ppm causes 60% loss in CO2 breakthrough capacity after 120 cycles. A simple amine reinfusion technique is successfully demonstrated to recover the adsorption capacity in poisoned fiber sorbents after deactivation by exposure to impurities such SO2. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3878–3887, 2014

Unusual pH-responsive fluid based on a simple tertiary amine surfactant: the formation of vesicles and wormlike micelles

A novel pH-responsive viscoelastic micellar system was prepared by N,N-dimethyl oleoaminde-propylamine without the addition of hydrotropes. The micellar system undergoes a gradual transition from vesicles to spherical micelles to wormlike micelles by adding an HCl solution. Rheology, Cryo-TEM and dynamic light scattering (DLS) results revealed that the pH-responsive flow behavior is attributed to the microstructural transition among the spherical micelles, vesicles and worm-like micelles. In this paper, we found out that a vesicle is extremely pH sensitive because the degree of protonation and the concentration of Cl− strongly affect the pH areas which could form worm-like micelles. The notable advantages of vesicles and worm-like micelles can be utilized to prepare pH-responsive viscoelastic fluids in the desired pH areas.

ChemInform Abstract: Asymmetric Aldol Reaction Using a Very Simple Primary Amine Catalyst: Divergent Stereoselectivity by Using 2,6‐Difluorophenyl Moiety.

AbstractSimple chiral amine catalysts (I) are successfully employed for the asymmetric aldol reaction of aromatic aldehydes and isatins with aliphatic ketones and aldehydes.

ChemInform Abstract: Asymmetric Organocatalytic Conjugate Addition of Dialkyl Phosphites to N‐Unprotected Isatylidene Malononitriles: Access to 3‐Phospho‐2‐oxindoles with Chiral Quaternary Stereocenters.

Abstract The enantioselective Michael addition of dialkyl phosphites to N-unprotected isatylidene malononitriles has been established for the first time by using a simple bifunctional tertiary amine–thiourea catalyst. The corresponding adducts, 3-phospho-2-oxindoles, containing a chiral quaternary carbon center at the 3-position of the oxindole, were obtained in good to excellent yields (up to 98%) with moderate to excellent enantioselectivities (up to 95% ee). In addition, optically active 3,3′-disubstituted oxindoles bearing carboxylate and phosphonate groups were facilely obtained by the oxidative degradation of the Michael adducts.