Tetra-n-butylammonium Hydroxide:an Efficient Catalyst for N-Alkylation of Pyrimidines and Purines

An efficient procedure for N-alkylation of pyrimidines and purines in the presence of tetra-n-butylammonium hydroxide（TBAH） is described. The method is very practical and the alkylation can occur at room temperature and the yields of the N-alkyl pyrimidines and purines were found to be excellent.

A NEW ONE-STEP REDUCTIVE N-ALKYLATION OF AMINO ACIDS AND THEIR ESTERS

The reductive alkylation of amine with carbonyl compounds using sodium hydrogen telluride has been investigated in recent years. Application of this method to the synthesis of N-alkyl derivatives of biologically important amino acids and their esters is described.

Cascade N-Alkylation/Hemiacetalization for Facile Construction of the Spiroketal Skeleton of Acortatarin Alkaloids with Therapeutic Potentiality in Diabetic Nephropathy

The concise building of the spiroketal core of acortatarin-type alkaloids as potential therapeutic agents in diabetic nephropathy was established in four steps,through a tandem N-alkylation/hemiacetalization between pyrrole units and the corresponding halo alcohols generated by convenient halomethylation of chiral lactones from natural aldoses.

Synergistic roles of platinum nanoparticles and sodium ions within beta zeolites in N-alkylation of amines with aromatic alcohols

N-alkylation of amines with alcohols is a promising green route for the synthesis of N-alkylamines, but the designation of highly active and stable heterogeneous catalysts remains one challenge. In this work, we initiated the application of zeolite-encapsulated noble metal nanoparticles(NPs) in the N-alkylation of amines with aromatic alcohols. Platinum(Pt) NPs were directly confined into the framework of BEA zeolite with tunable Si/Al molar ratios and Na^(+) contents. The champion catalyst afforded the extremely high turnover number(TON) of 6,176 and turnover frequency(TOF) of 3,390 h^(-1) plus stable recyclability and broad substrate compatibility. The Na ions modulated the electronic state of Pt NPs to reach a moderate Pt–H strength, which wellbalanced the two crucial steps of dehydrogenation and H-transfer and accounted for the high catalytic performance. The encapsulation of zeolites provided spatial satisfaction for the synergy effect above and enhanced the stabilization of Pt NPs.

Practical N-alkylation via homogeneous iridium-catalyzed direct reductive amination

Direct reductive amination(DRA)is one of the most efficient methods for amine synthesis.Herein we report a practical homogeneous DRA procedure utilizing iridium catalysis.Applying simple,readily available and inexpensive PPh_(3)and alike ligands along with iridium at a low loading,aldehydes and ketones reductively coupled with primary and secondary amines to efficiently form structurally and functionally diverse amine products,including a set of drugs and compounds from late-stage manipulation.The reaction conditions were exceptionally mild and additive-free,in which oxygen,moisture,polar protic groups and multiple other functional groups were tolerated.For targeted products,this methodology is especially versatile for offering multiple possible synthetic options.The 10 gram-scale synthesis further demonstrated the potential and promise of this procedure in practical amine synthesis.DFT studies reveal an“outer-sphere”H-addition pathway,in whichπ-πinteractions and H-bonding play important roles.

Palladium-Catalyzed N-Alkylation of Amides and Amines with Alcohols Employing the Aerobic Relay Race Methodology

Possibly because homogeneous palladium catalysts are not typical borrowing hydrogen catalysts and ligands are thus ineffective in catalyst activation under conventional anaerobic conditions, they had not been used in the N-alkylation reactions of amines/amides with alcohols in the past. By employing the aerobic relay race methodol- ogy with Pd-catalyzed aerobic alcohol oxidation being a more effective protocol for alcohol activation, ligand-free homogeneous palladiums are successfully used as active catalysts in the dehydrative N-alkylation reactions, giving high yields and selectivities of the alkylated amides and amines. Mechanistic studies implied that the reaction most probably proceeds via the novel relay race mechanism we recently discovered and proposed.

Rhodium-catalyzed aerobic N-alkylation of sulfonamides with alcohols

By using the famous Wilkinson＇s catalyst, N-alkylation of sulfonamides can be easily realized under mild aerobic conditions by using alcohols as the alkylating reagent, giving monoalkylated sulfonamides in high yields and selectivities with water produced as the only byproduct. This advantageous aerobic method is potentially general in substrate scope that it can also be applied to other amides, amines and alcohols.

Iron（lll）-Catalyzed Direct N-Alkylation of Azoles via Oxidative Transformation of sp3 C H Bonds under Solvent-Free Conditions

A new approach to synthesize N-alkylation of azoles by iron（III）-catalyst under solvent-free conditions was de- veloped. The method is broad in scope and highly efficient.

Direct N-alkylation of amines with alcohols using AlCl_3 as a Lewis acid

A substitution reaction of amines with alcohols for N-alkylated amines has been developed using inexpensive AlCl3without any ligand or additive.Either aromatic or aliphatic amines and primary or secondary alcohols perform the AlCl3-mediated reaction smoothly to afford various N-alkylated amines in satisfactory yields.

A Study on Dynamics of Drug Release from N-alkyl Chitosan Derivative Membranes In Vitro

The diffusion coefficient of model drugs (Sodium benzoate, Lysozyme and Ribonuclease) through chitosan and N-alkyl chitosan membranes were measured by using ’lag time’ technique. The results indicate that the release mechanism for the drug with small molecular weight is predominantly of ’pore type’, and for the drug with high molecular weight is predominantly pf ’partition type’. The release of protein drug with higher hydrophobicity enhances as the size of N-alkyl group and its substitution degree of chitosan increase.

Synthesis and antibacterial evaluation of 2-substituted-4,5-diphenyl-N-alkyl imidazole derivatives

Objective:To synthesis 2-substituted-4,5-diphenyl-N- alkyl imidazole derivatives,and evaluate their antibacterial activity.Methods:A mixture of benzil（10 mmol） and ammonium acetate（0.1 mol）（immediately fused） in glacial acetic acid（25 mL） was stirred at 80-100℃for 1 h under nitrogen atmosphere（to prevent incorporation of any atmospheric impurities and moisture）. Substituted aldehydes（10 mmol） in glacial acetic acid（5 mL） was added drop-wise over a period of 15-20 min at the same temperature and stirred for another 4 h,the progress of the reaction was monitored by TLC test using ethyl acetate as eluent.The newly synthesized compounds were characterized by IR,1HNMR,13CNMR and by mass spectroscopy.Results:All the synthesized compounds were confirmed by spectroscopical techniques and evaluated for antimicrobial activity against Staphylococcus aureus（S.aurius）,Bacilus subtilus（B.subtilus）,and Escheria coli （E.coli）.These compounds showed antibacterial activity（zone of inhibition） against S.aurius ranged from 3 mm to 9 mmin diameter,B.subtilus,4 -8 mm,and E.coli 5 -12 mm.Out of 2a-2e, only 2a and 2b showed some sort of activity but none of them had considerable activity compared with that of the standard.Conclusions:All the synthesized compounds show moderate activity against the tested bacteria S.aurius,B.subtilus,and E.coli.So,further structural modification is necessary to improve the antibacterial action of 2-substituted-4,5-diphenyl-N-alkyl imidazole derivatives.

Synthesis and Crystal Structure of a New N-alkylated Azacrown Ligand

A new pendant arms macrocyclic ligand, N, N'-bis(2-cyanoethyl)-3,4: 9, 10-dibenzo-1, 12-diaza-5, 8-dioxacyclopentadecane (L), was synthesized in goodyield (93% ) by alkylating 3, 4: 9, 10-dibenzo-1, 12-diaza-5, 8-dioxacyclopentadecane(L') with acrylonitrile. Its crystal structure has been determined by X-ray diffraction.The ligand crystallizes in the orthorhombic system, space group Pbca, a=18. 143 (3),b=11. 206(2), c=22. 274(5)A, V=4528(2)A3, Mr=418. 55, Z= 8, F(000)=1792, Dc= 1. 228 gcm-3, T= 293K, μ= 7. 9 cm-1, final R=0.044 and Rw=0.067(w=1/(σ2 (F) + 0. 0005F2 ) ) based on 2291 independent reflections with F> 4. 0σ(F). The two benzene rings of the macrocyclic ligand are not in the same plane, andthe dihedral angle between them is 73. 6°, the molecule is in a folded state.

Synthesis of 3-Alkyl-5-Benzylidene-2,4-Thiazolidinedione Under Microwave Irradiation

Microwave irradiation of aromatic aldehyde and 2,4-thiazolidinedione provides a fast and high-yield access to 5-benzylidene-2,4-thiazolidinedione. Seven 3-alkyl-5-benzylidene-2,4-thiazolidinedione compounds were produced with high yield by reacting 5-benzylidene-2,4-thiazolidinedione with different alkylating agents under microwave irradiation.

^(13)C NMR STUDIES ON DYNAMICS OF POLY (n - ALKYL METHACRYLATES)

The dynamics of a series of poly(n-alkyl methacrylates) is investigated by means of ^(13)C spin-lattice relaxation experiments. The results show that the dynamics has the polymer property dependence.

Analogs of Antifungal Indoles Isolated from Aporpium Caryae with Activity Against Sudden-Death Syndrome of Soybean

Based on the precedent discovery of a weak antifungal indole isolated from Aporpium caryae, which increased its activity when changing the N-alkyl chain, nineteen N-alkyl indoles, with alkyl chains from one to ten carbons and one or two hydroxyls, one amine or bromine functional groups, were prepared and fully characterized by spectroscopic methods. The aim of this study is the search for new synthetic agrochemical leads derived from natural products. The antifungal activity of the synthesized compounds against three fungal strains was measured in vitro. Six compounds presented good activity against Fusarium virguliforme, the causal agent of sudden-death syndrome (SDS) in soybean, in a bioautography assay. Four of them were tested in a germination test and in a greenhouse experiment. All tested compounds, applied as seed treatment, showed antifungal properties being effective to control SDS when there was low level of fungal contamination. Results indicate that some of the tested compounds are acting as growth inhibitors and represent new leads for the treatment of SDS for which no specific treatment has been previously reported.

Iron-nickel alloy particles with N-doped carbon “armor” as a highly selective and long-lasting catalyst for the synthesis of Nbenzylaniline molecules

A scalable strategy for the convenient and rapid preparation of nitrogen-doped carbon-coated iron-based alloy catalysts was developed.By controlling the type and amount of metal salts in the precursor,various types of nitrogen-doped carbon-coated alloy catalysts can be prepared in a targeted manner.Fe_(2)Ni2@CN materials with small particle sizes and relatively homogeneous basic sites showed promising results in the N-alkylation reaction of benzyl alcohol with aniline(optimum yield:99%).It is worth noting that the catalyst can also be magnetically separated and recovered after the reaction,and its performance can be regenerated through simple calcination.Furthermore,it was confirmed by kinetic experiments that the activation of C–H at the benzyl alcohol benzylic position is the rate-determining step(RDS).According to density flooding theory calculations,Fe_(2)Ni2@CN catalysts require less energy than other materials(Fe@CN and Ni@CN)for the RDS(dehydrogenation reaction)process.Therefore N-alkylation reactions are more easily carried out on Fe_(2)Ni2@CN catalysts,which may be the reason for the best catalytic activity of Fe-Ni alloy materials.These carbon-coated alloy materials will show great potential in more types of heterogeneous catalysis.

Tuning the Johari-Goldstein β-Relaxation and Its Separation from α-Relaxation of Poly(n-alkyl methacrylate)s by Small Molecule-bridged Hydrogen Bonds

Introducing small molecule-bridged hydrogen bonds(HBs)between polymer chains has been reported to effectively reduce the interchain cooperativity despite of strengthening the intermolecular interaction.Here,a systematic investigation on tuning the Johari-Goldsteinβ(βJG)relaxation by adding various low-molecular-weight phenols in poly(n-alkyl methacrylate)s is carried out to further clarify the anomalous dynamics.Given these small molecules capable of coupling the motion with pendent groups of host polymers due to forming at least two HBs per molecule,poly(n-alkyl methacrylate)mixtures exhibit rich dynamic changes in theβJG-properties andα,βJG separations.An increased loading of phenols with a small size and strong inter-HB strength(Δυi)clearly benefits for significant retardation and suppression of theβJG-relaxation,narrows theα,βJG separation and converges theβJG-peak with theα-peak,which demonstrates the alleviation of inter-chain topological constraints.However,small molecules with a relatively big size and weakΔυi are found to amplify the magnitude of theα,βJG separation of poly(butyl methacrylate),even though experimental results of changes inα-dispersion and dynamic fragility confirm a reduction of the coupling factor n in all of these hybrids.The counterintuitive phenomenon suggests that the crossover time tc in the Coupling Model is no longer a universal quantity if the inter-chain interaction of polymers is strengthened by HBs.These compelling findings shed vital insights into the HBinduced anomalous dynamics,and provide essential guidance for tailoring theβJG behavior and designing glassy polymeric materials.

Limited Fraction of Crystallized Side Chains in Bottlebrush Poly(n-alkyl methacrylate)s

Crystallinity of bottlebrush polymers due to side chain crystallization has been considered to be related to the length of the side chains only under the assumption of complete participation of crystallization by all sidechains.Recent experimental results revealed that in poly(n-alkyl methacrylate)s a fraction of side chains could not crystallize due to constraints imposed by the trapped main chain entanglements and required expansi on of main chain-main chain distanee.This result renders the original simplified con sideration of the origin of crystallinity in bottlebrush polymers questionable.In this work,we introduce a new parameter f_(c),the fraction of crystallizable side chains,to better describe the crystallinity of bottlebrush polymers.A lin earrelati on ship between the meltingenthalpy and the number of alkyl groups in side chains for bottlebrush polymers reported repeatedly indicates that f_(c) remains essentially unchanged when bottlebrush polymers had the same main chain structure and grafting degree but different side chain lengths.The slope of the above-mentioned linear relationship is thus △H_(CH2)xf_(c),where △H_(CH2) stands for the melting enthalpy of one mole alkyl group packed into the crystal.With a known value of f_(c),it is possible to estimate the value of △H_(CH_(2)).In case of poly(n-alkyl methacrylate)s,we estimated △H_(CH_(2)) of hexagonal crystal being at most 5.74 kJ/mol with the knowledge of possibly smallest f_(c) of 0.67 obtained from small angle X-ray scattering data.Therefore,the crystallinity of bottlebrush polymer would be calculated based on the equati on X_(c)=f_(c)×N_(c)/N with N and N_(c) being the nu mber of alkyl groups in a side chain and those packed in the crystalline structure,respectively.Both chemical structure and grafting degree of bottlebrush polymers affect f_(c).

Synthesis of chiral N-alkylated indoles through replacement of aniline nitrogen by natural amino acids

Chiral N-alkylated indoles are privileged structural motifs found in many natural products and pharmaceuticals and a search for effective methods with which to prepare chiral N-alkylated indoles is ongoing.Efficient syntheses of enantioenriched N-alkylated indoles has been developed but not with standing these advances,the develop-ment of a facile method to prepare chiral N-alkylated indoles from simple and available starting materials under mild conditions is still needed.In this paper,we report a nitrogen replacement process driven by dearomatization that directly incorporates naturalα-amino acids into 2-alkynylanilines leading to the formation of a variety of multi-functional chiral N-alkylated indoles.

Strong dual-state emission of unsymmetrical and symmetrical thiazolothiazole-bridged imidazolium salts

A novel thiazolothiazole-bridged imidazole derivative(1) was found to exhibit blue fluorescence in gaseous state or in methanol and yellow fluorescence in solid state. The N-alkylation of imidazole subunit(s) in 1 using n-propyl iodide generated unsymmetrically or symmetrically alkylated thiazolothiazolebridged imidazolium salts with good water solubility and remarkably strong emission in solution. Furthermore, the replacement of iodide counter-anion by triflate or bis(trifluoromethane sulfonyl)imide achieved remarkably strong emission in solid state and in solution as well as good water solubility. The strong fluorescence of dicationic salts with triflate and NTf_(2)^(-)counter-anions in solid state can be ascribed to their twisted and rigid structures induced by interionic C-H···F hydrogen bonding.