Presence Of 4-dimethylaminopyridine Research Articles

One-Step Conversion of Potassium Organotrifluoroborates to Metal Organoborohydrides.

This letter describes the one-step conversion of heteroatom-substituted potassium organotrifluoroborates (KRBF3) to metal monoorganoborohydrides (MRBH3) using alkali metal aluminum hydrides. The method tolerates a variety of functional groups, expanding MRBH3 diversity. Hydride removal with Me3SiCl in the presence of dimethylaminopyridine (DMAP) affords the organoborane·DMAP (RBH2·DMAP) adducts.

FLAVONOID COMPOUNDS FROM ARTEMISIA GLABELLA KAR. ET. KIR., SYNTHESIS ON THEIR BASIS AND BIOLOGICAL ACTIVITY

As a result of complex chemical processing of medicinal raw materials of Artemisia glabella Kar. et Kir., including CO2 extraction and lactones isolation, we have investigated the chemical composition of flavonoids to select the biologically active ones and carry out modifications on their basis. Two flavonoids pectolinaringenin and cirsilineol have been isolated by partition chromatography from the secondary raw materials of Artemisia glabella Kar. et. Kir. and identified. To obtain new biologically active compounds, we have synthesized new amino derivatives of cirsilineol by the Mannich reaction with secondary amines (piperidine and N-methylpiperazine) in isopropanol with the presence of dimethylaminopyridine. In proton NMR spectrum of the synthesized compounds there are proton signals of the initial cirsilineol fragment; however, there is no N-8 proton signal, besides other signals typical for amines’ benzene ring have been observed at 1.53–3.90 ppm. It means that reaction occurred at the C-8 position of carbon in ring A. The synthesized compounds have been studied for various types of biological activity typical for this class, including hepatoprotective and anti-inflammatory activities. Amino derivatives of cirsilineol exhibit a moderate activity against HepG2 cell line, while cirsilineol at a dose of 5 mg/ml expresses a pronounced hepatoprotective activity. Moreover, all samples at a dose of 25 mg/kg show poor anti-inflammatory effects on the model of acute exudative reaction in vivo.

Improved ionic conductivity in guar gum succinate–based polymer electrolyte membrane

Guar gum succinate (GGS) was chemically modified by reacting guar gum with succinic anhydride in the presence of 4-dimethylaminopyridine. Succination was confirmed by Fourier transform infrared (FTIR) spectroscopy with carbonyl bands at 1724 cm−1 and ester linkage at 1567 cm−1 of the succinate group. The resulting amorphous, GGS was used as a polymer host to prepare cost-effective solid polymer electrolyte (SPE) films via incorporating a blend of ethylene carbonate (EC), carboxymethyl cellulose (CMC), lithium triflate (LiTf) and lithium iodide (LiI). SPE system for GGS:EC (1.0:0.6) with 30 wt% LiTf showed highest conductivity of 6.29 × 10−5 S cm−1 and GGS:CMC:EC (0.5:0.5:0.6) with 25 wt% LiI showed highest conductivity of 2.10 × 10−4 S cm−1. FTIR revealed multiple complexation sites for ion mobility indicating that GGS possesses high prospects as a conductive SPE.

Asymmetric Conjugate Addition of α,α-Disubstituted Aldehydes to Nitroalkenes Organocatalyzed by Chiral Monosalicylamides from trans-Cyclohexane-1,2-Diamines.

Primary amine-salicylamides derived from chiral trans-cyclohexane-1,2-diamines are used as organocatalysts for the enantioselective conjugate addition of α,α-disubstituted aldehydes to arylated and heteroarylated nitroalkenes. The reaction is performed in the presence of 4-dimethylaminopyridine as an additive in dichloromethane as a solvent at room temperature. The corresponding enantioenriched γ-nitroaldehydes are obtained with enantioselectivities up to 95%. Theoretical calculations are used to justify the reasons of the stereoinduction.

High-Tg, Low-Dielectric Epoxy Thermosets Derived from Methacrylate-Containing Polyimides.

Three methacrylate-containing polyimides (Px–MMA; x = 1–3) were prepared from the esterification of hydroxyl-containing polyimides (Px–OH; x = 1–3) with methacrylic anhydride. Px–MMA exhibits active ester linkages (Ph–O–C(=O)–) that can react with epoxy in the presence of 4-dimethylaminopyridine (DMAP), so Px–MMA acted as a curing agent for a dicyclopentadiene-phenol epoxy (HP7200) to prepare epoxy thermosets (Px–MMA/HP7200; x = 1–3) thermosets. For property comparisons, P1–OH/HP7200 thermosets were also prepared. The reaction between active ester and epoxy results in an ester linkage, which is less polar than secondary alcohol resulting from the reaction between phenolic OH and epoxy, so P1–MMA/HP7200 are more hydrophobic and exhibit better dielectric properties than P1–OH/HP7200. The double bond of methacrylate can cure at higher temperatures, leading to epoxy thermosets with a high-Tg and moderate-to-low dielectric properties.

TEMPO-Mediated Synthesis of Tetrahydropyridinofullerenes: Reaction of [60]Fullerene with α-Methyl-Substituted Arylmethanamines and Aldehydes in the Presence of 4-Dimethylaminopyridine.

A series of scarce tetrahydropyridinofullerenes were synthesized by the metal-free-mediated reaction of [60]fullerene with cheap and easily available α-methyl-substituted arylmethanamines and aldehydes in the presence of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and 4-dimethylaminopyridine (DMAP) in moderate to good yields comparable to the previously reported data for most monoadducts. The in situ generation of azadienes played a crucial role in the successful synthesis of tetrahydropyridinofullerenes. A plausible reaction mechanism was proposed to elucidate the reaction process.

Template-Free Electroless Plating of Gold Nanowires: Direct Surface Functionalization with Shape-Selective Nanostructures for Electrochemical Applications.

Metal nanowires (NWs) represent a prominent nanomaterial class, the interest in which is fueled by their tunable properties as well as their excellent performance in, for example, sensing, catalysis, and plasmonics. Synthetic approaches to obtain metal NWs mostly produce colloids or rely on templates. Integrating such nanowires into devices necessitates additional fabrication steps, such as template removal, nanostructure purification, or attachment. Here, we describe the development of a facile electroless plating protocol for the direct deposition of gold nanowire films, requiring neither templates nor complex instrumentation. The method is general, producing three-dimensional nanowire structures on substrates of varying shape and composition, with different seed types. The aqueous plating bath is prepared by ligand exchange and partial reduction of tetrachloroauric acid in the presence of 4-dimethylaminopyridine and formaldehyde. Gold deposition proceeds by nucleation of new grains on existing nanostructure tips and thus selectively produces curvy, polycrystalline nanowires of high aspect ratio. The nanofabrication potential of this method is demonstrated by producing a sensor electrode, whose performance is comparable to that of known nanostructures and discussed in terms of the catalyst architecture. Due to its flexibility and simplicity, shape-selective electroless plating is a promising new tool for functionalizing surfaces with anisotropic metal nanostructures.

Towards phosphine-free Pd(II) pincer complexes for catalyzing Suzuki-Miyaura cross-coupling reaction in aqueous medium

Pincer complexes can act as efficient catalysts for many industrially important organic transformations under environmentally benign and mild conditions. The NNN pincer ligands have been prepared from the reactions between pyridine-2,6-dicarbonyldichloride and benzylamine or its derivatives in the presence of 4-dimethylaminopyridine (DMAP). Pd(II) complexes containing NNN pincer ligand and acetonitrile/triphenylphosphine have been synthesized and characterized by analytical, spectroscopic (FT-IR, UV-Visible, 1H, 13C &31P NMR and Mass) and single crystal X-ray diffraction techniques. Single crystal X-ray analysis reveals a distorted square planar geometry around Pd in all the complexes. These pincer complexes have been used as catalysts in Suzuki-Miyaura cross-coupling reaction. The effect of ancillary ligands (CH3CN and PPh3) in the complexes has been investigated towards the coupling reaction. The conversions have been determined from GC analyses. Scope of the system has been extended with various substituted halides.

Novel one-component molecular glass photoresist based on cyclotriphosphazene containing t-butyloxy carbonyl group for i-line lithography

Hexakis(4-formylphenoxy) cyclotriphosphazene (HAPCP), substitution reaction product of hexachlorotriphosphazene (HCTP) with p-hydroxybenzaldehyde, was reduced by sodium borohydride to afford hexakis[4-(hydroxymethyl) phenoxyl] cyclotriphosphazene (HHPCP). The hydroxyl group of this compound was then protected by the reaction with di-tert-butyl dicarbonate ester (DBDC) in the presence of 4-dimethylaminopyridine (DMAP) as catalyst to give t-butyloxy carbonyl (tBOC) protected HHPCP. Fourier-transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (1H NMR) were employed to characterize the chemical structure, indicating that the synthesis was successful. Thermal behavior was characterized by thermogravimetric analysis (TGA), the results showed that the initial thermal decomposition temperature occurred at approximately 170 °C, X-ray diffraction analysis (XRD) results showed that the tBOC protected HHPCP derivatives had amorphous form, and performed excellent film-forming property. Upon irradiation to 365 nm exposure, the photoacid generated proton H+, which can catalyze the deprotection of acid labile tBOC group. This type of novel molecular glass photoresist based on hexachlorotriphosphazene showed high sensitivity, making it possible to fabricate 1 μm line and space pattern under i-line exposure.

Synthesis and properties of carboxy derivative of Epidian 6 monomethacrylate

We present the synthesis of an oligomer with carboxy and methacrylic groups based on Epidian 6. The effect of the catalyst nature and amount, solvent nature and process temperature on the rate of the reaction between Epidian6 monomethacrylate and adipic acid was examined at 313, 323 and 333 K in the presence of 4-dimethylaminopyridine, 1,4-diazobicyclo[2.2.2]octane, and benzyltriammonium chloride. The synthesized oligomer was characterized using chemical and IR-spectroscopic analyses. We suggest the use of the synthesized product as an active additive to epoxy-oligoesteric blends based on Epidian 5. The chemistry of the film forming process has been determined using IR-spectroscopy.

One-pot synthesis of molecular glass photoresists based on β-cyclodextrin containing a t-butyloxy carbonyl group for i-line lithography

Positive chemically amplified molecular glass with pendant t-butyloxy carbonyl (t-BOC) groups based on β-cyclodextrin (β-CD) was prepared. The β-CD derivatives were obtained from the reaction of β-CD and di-tert-butyl dicarbonate (DBDC) in the presence of 4-dimethylaminopyridine, and the protecting ratio was controlled using various feed amounts of DBDC. Fourier-transform infrared spectroscopy and proton nuclear magnetic resonance were employed to characterize the chemical structure, indicating that the synthesis was successful. Thermal behavior was characterized by thermogravimetric analysis; the results showed that the initial thermal decomposition temperature occurred at approximately 160 °C, which could satisfy the lithography process. Ultraviolet–visible spectrophotometer indicated that the t-BOC-protected β-CD derivatives had low absorbance at 365 nm wavelength. Additionally, X-ray diffraction analysis results showed that the β-CD derivatives had amorphous form, and exhibited excellent film-forming property. The photoresists consisting of different t-BOC protecting groups showed high sensitivity when exposed to 365 nm light and post-baked at 105 °C for 90 s, followed by developing in 2.38 wt% aqueous tetramethylammonium hydroxide solution at room temperature. An enhanced line and space positive patterns with 1 μm resolution were delineated according to digital microscope.

Donor/Acceptor-Stabilized 1-Silaketene: Reversible [2+2] Cycloaddition with Pyridine and Evolution by an Olefin Metathesis Reaction.

The reaction of silacyclopropylidene 1 with benzaldehyde generates a 1-silaketene complex 2 by a formal atomic silicon insertion into the C=O bond of the aldehyde. The highly reactive 1-silaketene 2 undergoes a reversible [2+2] cycloaddition with pyridine to give sila-β-lactam 3. Of particular interest, in the presence of 4-dimethylaminopyridine (DMAP), 1-silaketene complex 2 evolves through an intramolecular olefin metathesis reaction, generating a new 1-silaketene complex 8 and cis-stilbene. Theoretical studies suggest that the reaction proceeds through the formation of a transient silacyclobutanone, a four-membered-ring intermediate, similar to that proposed by Chauvin and co-workers for the transition-metal-based olefin metathesis.

Synthesis, Characterization, and Crystal Structure of Two Novel Diiron Dithiolate Complexes Bearing Thiolate-Bridged-Carboxy Functionality

Two new diiron dithiolate complexes [(μ-SCH2)2CHCO2R][Fe2(CO)6] (R = -C10H7-β, 1; -C6H4Me-m, 2) bearing thiolate-bridged-carboxy functionality, which are closely related to the active site of [FeFe]-hydrogenase, have been synthesized by esterification reaction of parent complex [(μ-SCH2)2CHCO2H][Fe2(CO)6] (A) and C10H7OH-β or HOC6H4Me-m in the presence of 4-dimethylaminopyridine (DMAP) and dicyclohexylcarbodiimide (DCC). These new complexes were characterized by elemental analysis, FTIR, as well as 1H (13C) NMR spectroscopy, and particularly for 1 by X-ray crystallography. Furthermore, the thiolate-bridged-carboxy functionality (namely, the ester group) resides in an equatorial position in the chair conformation of the six-membered rings (FeS2C3) in crystal structure of 1.

Guar gum succinate as a carrier for colon-specific drug delivery

A novel type of pH-sensitive colon-specific controlled drug delivery carrier based on guar gum succinate (GGS) was prepared by reacting guar gum (GG) with succinic anhydride (SA) in the presence of 4-dimethylaminopyridine (DMAP). The formation of GGS was confirmed by FT-IR and 1H NMR and characterized using XRD techniques. GGS microparticles with 460–740μm in size were prepared using sodium trimetaphosphate (STMP) as a cross-linking agent. The size and morphologies of GGS microparticles were assessed by scanning electron microscopy (SEM). The swelling degree of the GGS microparticles was found to be higher in pH 7.4 than in pH 1.2. In addition, GGS microparticles showed a pH dependent drug release profile when compared to the GG microparticles. The MTT assay revealed that there is no apparent cytotoxicity of GGS against a mouse mesenchymal stem cell line at a concentration range of 0–200μg/ml. These results confirm that GGS could be used as a carrier for colon-specific drug delivery.

On the Functional Group Tolerance of Ester Hydrogenation and Polyester Depolymerisation Catalysed by Ruthenium Complexes of Tridentate Aminophosphine Ligands.

The synthesis of a range of phosphine-diamine, phosphine-amino-alcohol, and phosphine-amino-amide ligands and their ruthenium(II) complexes are reported. Five of these were characterised by X-ray crystallography. The activities of this collection of catalysts were initially compared for the hydrogenation of two model ester hydrogenations. Catalyst turnover frequencies up to 2400 h(-1) were observed at 85 °C. However, turnover is slow at near ambient temperatures. By using a phosphine-diamine Ru(II) complex, identified as the most active catalyst, a range of aromatic esters were reduced in high yield. The hydrogenation of alkene-, diene-, and alkyne-functionalised esters was also studied. Substrates with a remote, but reactive terminal alkene substituent could be reduced chemoselectively in the presence of 4-dimethylaminopyridine (DMAP) co-catalyst. The chemoselective reduction of the ester function in conjugated dienoate ethyl sorbate could deliver (2E,4E)-hexa-2,4-dien-1-ol, a precursor to leaf alcohol. The monounsaturated alcohol (E)-hex-4-en-1-ol was produced with reasonable selectivity, but complete chemoselectivity of C=O over the diene is elusive. High chemoselectivity for the reduction of an ester over an alkyne group was observed in the hydrogenation of an alkynoate for the first time. The catalysts were also active in the depolymerisation reduction of samples of waste poly(ethylene terephthalate) (PET) to produce benzene dimethanol. These depolymerisations were found to be poisoned by the ethylene glycol side product, although good yields could still be achieved.

Sustainable alternative protocols for the multicomponent synthesis of spiro-4H-pyrans catalyzed by 4-dimethylaminopyridine

Green approaches to the synthesis of spiro-4H-pyrans are reported based on the one-pot and three-component condensation via a domino Knoevenagel/Michael/cyclization sequence. These approaches involve evaluation of the activity of several organocatalysts in water as a reaction media and also under solvent-free in both microwave irradiation and ball milling conditions. Extensive experiments were carried out to optimize the reaction parameters including type and amount of catalyst, reaction temperature and time. Microwave irradiation in presence of 4-dimethylaminopyridine (DMAP) was observed as the best procedure with good yields, short reaction time, environmental friendliness, and convenient operation.

Stereoselective synthesis of chiral sulfilimines from N-mesyloxycarbamates: metal-nitrenes versus metal-nitrenoids species.

The synthesis of a variety of chiral sulfilimines and sulfoximines is described. The amination of thioethers with a chiral N-mesyloxycarbamate was achieved in high yields and stereoselectivities using Rh2[(S)-nttl]4 as catalyst in the presence of 4-dimethylaminopyridine (DMAP) and a pyridinium salt, such as bis(DMAP)CH2Cl2 or a viologen salt. These additives proved instrumental to enhance both the yield and the stereochemical discrimination of the reaction. Mechanistic studies and control experiments have elucidated the role of these additives. DMAP served as an apical ligand for the rhodium catalyst: an X-ray crystal structure of the (DMAP)2·[Rh2{(S)-nttl}4] complex was obtained. This complex displayed a lower and irreversible redox potential. Control experiments with preformed Rh(II)-Rh(III) complex suggested such a catalytically active species in the thioether amination process. Diastereoselectivities were influenced by the sulfonyloxy leaving group, ruling out the possibility of a common metal nitrene species and instead suggesting a rhodium-nitrenoid complex. It is believed that the bispyridinium salt played the role of a phase transfer catalyst, influencing both the yield and the diastereoselectivity of the reaction.

Synthesis, crystal structures and electrocatalytic properties of bridgehead-C-functionalized diiron dithiolate complexes

To investigate the influence of bridgehead-C functionality in diiron dithiolate complexes on the molecular structure and electrocatalytic properties of [FeFe]-hydrogenase models, three new bridgehead-C-functionalized model complexes 1–3 have been synthesized and structurally characterized. Treatments of parent complex [(μ-SCH2)2CHCO2H][Fe2(CO)6] (A) with the esterification agents o-MeC6H4OH, p-ClC6H4OH, or p-HOC6H4CHO in the presence of 4-dimethylaminopyridine and dicyclohexylcarbodiimide in CH2Cl2 at room temperature resulted in formation of [(μ-SCH2)2CHCO2R][Fe2(CO)6] (R = o-MeC6H4–, 1; p-ClC6H4–, 2; p-OHCC6H4–, 3) in 53–55% yields. The new complexes 1–3 were characterized by elemental analysis, IR and NMR spectroscopy, and especially determined by X-ray crystallography. The electrochemical properties of 1–3 and the electrocatalytic H2 evolution catalyzed by 1 have been investigated by cyclic voltammetry, where 1 is a catalyst for HOAc proton reduction to H2 under electrochemical conditions.

Green methacrylated lignin model compounds as reactive monomers with low VOC emission for thermosetting resins

AbstractMethacrylated lignin model compounds (LMCs, i.e., eugenol and guaiacol) monomers are ideal candidates as styrene replacements because they have low volatilities and can free-radically polymerize with vinyl ester resins. This article reports the synthesis of methacrylated eugenol (ME), methacrylated guaiacol (MG) using LMCs and methacrylic anhydride in the presence of 4-dimethylaminopyridine (DMAP) as a catalyst. ME and MG were characterized using FT-IR,

Mono/multinuclear cobaloxime and organocobaloxime-catalyzed conversion of CO2 and epoxides to cyclic organic carbonates: Synthesis and characterization

The synthesis and characterization of the mono- and multinuclear cobaloxime and organocobaloxime complexes bearing bidentate dimethyl glyoxime ligands are presented. All mono- and multinuclear cobaloxime and organocobaloxime complexes are used as catalysts for the cycloaddition of CO2 to various epoxides, especially epichlorohydrin, in the presence of 4-dimethylamino pyridine (DMAP) as a cocatalyst. In the catalytic applications, DMAP was a more active base with higher yield compared to other Lewis bases. Complexes (1) and (3), which have two dimethyl glyoxime per cobalt center (mononuclear complexes), are better catalytic systems than the corresponding multinuclear cobaloxime and organocobaloxime complexes (2–5) and (7–10) with two dimethyl glyoxime per cobalt center and one linked ligands per copper center. In addition, the organocobaloxime complex (6) showed the highest activity for the cycloaddition of CO2 with epichlorohydrin in the presence of 4-dimethylamino pyridine (DMAP) as cocatalyst. The used as catalysts mono- and multinuclear cobaloxime and organocobaloxime complexes were characterized by 1H and 13C NMR spectra, FT-IR spectra, UV–vis spectra, LC-MS spectra, molar conductivity measurements, melting point measurements and magnetic susceptibility measurements.