Interactions Balancing Competition and Cooperation between Covalent-Organic Framework Additives and PEG Base Oil toward Advanced Lubrication.

Severe competition between nanolubricant additives and polar lubricating oil molecules for the formation of lubricant films has been hindering the progress of green and advanced lubricants. In this work, based on the tautomerism of cyanuric acid molecule (trione and triol configurations), two kinds of triazine-based covalent-organic frameworks (COFs), that is, Ton-COFs and Tol-COFs, were synthesized as additives of the polar PEG 400 oil, realizing compromise between them by providing delicate interactions. The triazine matrix bonding with intense polar groups in the framework of additives offers more powerful interactions to competitively form the adsorbed lubricant film on the surface of the metal substrate over PEG 400 oil and also bolts PEG 400 oil molecules by the hydrogen bonding inside the pore of the framework to cooperatively bear against the load. Molecular quantum chemical calculations further confirm that Ton-COFs can produce a more intense interaction with Fe atoms in the form of coordination and ions···π than Tol-COFs, far beyond PEG 400, and the cross-sectional profile of the worn surface definitely exhibits a protective lubricant film only composed of Ton-COFs. Consequently, at the low concentration of 0.3 wt %, the excellent friction reduction (41.2%) and antiwear property (97.4%) are achieved for the Ton-COFs compared to pure PEG 400 oil; moreover, 28.6% and 79.0% for Tol-COFs at the essential concentration of 0.7 wt % are achieved. This finding provides a novel insight from molecules to materials into guiding the development of additives for advanced lubricants.

Ester Oils Prepared from Fully Renewable Resources and Their Lubricant Base Oil Properties.

The work reports on the physicochemical and tribological properties of gallate ester oils prepared from fully renewable resources, such as gallic acid and fatty acids. The ester structures were identified by proton nuclear magnetic resonance spectroscopy (1H NMR), carbon nuclear magnetic resonance spectroscopy (13C NMR) and high-resolution mass spectra (HRMS) data. The density at 20 °C (d 20), kinematic viscosity (KV), viscosity index (VI), pour point (PP), flash point (FP), thermal and oxidative stabilities, friction-reducing and antiwear properties of gallate ester oils were evaluated. The tribological properties of gallate ester oils as lubricants for steel, copper, and aluminum tribo-pairs can be compared with those of the commercially available lubricating oil tris(2-ethylhexyl) trimellitate (Phe-3Ci8), but their viscosity-temperature characteristics, thermal and oxidative stabilities are better than those of Phe-3Ci8. More importantly, they have much higher biodegradabilities than Phe-3Ci8. The study of the lubrication mechanism shows that the physical and/or chemical adsorption film formed by gallate ester molecules between friction pairs is the key factor for them to obtain friction-reducing and antiwear properties.

Multilayer Tribofilm: An Unique Structure to Strengthen Interface Tribological Behaviors.

Tribofilm configuration under the boundary lubrication region is an essential concern to gain insight into the tribological enhancement of the two-dimensional (2D) nano materials toward base oils. In this work, several alkyl carboxylic acids modified 2D triazine-based covalent organic frameworks (ATC) nano platelets were fabricated and served as lubrication additives. When carbon atoms add up to 16, the best lubricating performance is exhibited at an additive concentration of 0.05 wt % and the friction coefficient and wear volume are, respectively, reduced by 56.0% and 89.6% as compared to those of pure PAO 10 base oil. The analysis of the focused ion beam-transmission electron microscope (FIB-TEM) on the worn surface reveals that an alternately multilayer tribofilm consisting of 2D platelet additives and oxides and/or metallic soap salts is formed on the frictional interface of steel substrate, with a well-ordered arrangement along the sliding direction, which dominates the contributions of the excellent lubrication.

Iron-Catalyzed Cycloaddition of Amides and 2,3-Diaryl-2H-azirines To Access Oxazoles via C-N Bond Cleavage.

A novel and efficient iron-catalyzed cycloaddition reaction using readily available 2,3-diaryl-2H-azirines and primary amides is reported. A wide range of trisubstituted oxazoles could be achieved in good yields with good functional group compatibility. In this transformation, two C-N bonds were cleaed and new C-N and C-O bonds were formed.

Solvothermal Reaction and Piezoelectric Response of Oriented KNbO3 Polycrystals.

KNbO3 (KN) piezoelectric polycrystals were prepared by a two-step solvothermal reaction process with the managed organic solvents as reaction mediums at a low temperature for a short time. In the solvothermal reaction system, the formation mechanism of polycrystalline KN is mainly the dissolution-deposition mechanism. The influences of alkalinity, viscosity, and the polarity for reaction mediums on the formation of the niobates were investigated. The chemical reaction mechanisms of niobate products and formation mechanism of niobate crystals from the precursor were clarified. The regulating and controlling mechanism of the phase compositions, the morphologies, and the lattice constants for the niobates obtained in varied reaction mediums were revealed. The obtained KN piezoelectric polycrystals are constructed from oriented KN nanocrystals. Piezoelectric hysteresis loops of cuboid KN polycrystals were detected for the first time. A prepared cuboid KN polycrystal shows an average d33* value of 32 pm/V. The study provides a strategy for the development of oriented KN piezoelectric materials to apply the orientation engineering.

Toxic effect of three imidazole ionic liquids on two terrestrial plants.

To determine the toxic effect of three imidazole ionic liquids (IILs) in terrestrial monocotyledonous and dicotyledonous plants, three IILs (1-butyl-3-methylimidazole tetrafluoroborate, 1-butyl-3-methylimidazole hexafluorophosphate, and butyl-3-methylimidazolium bi-[(trifluoromethyl)sulfonyl]imide) were investigated using rice and capsicum as target toxicity models. In hydroponic experiments, increasing the concentration of the IILs led to a decrease in the seed germination rate, a decrease in the reduced stem and root lengths, and an increase in the inhibition rate of the stem and root lengths; in addition, as the concentration increased, the reducing sugar content of rice and capsicum seedling leaves and roots first increased and then decreased, while permeability of the cell membranes of the stems and roots of the two plants also gradually increased. In terms of the effects on these indices in rice, the ranking of these three IIL anions was [TF2N]- > [PF6]- > [BF4]-; in terms of the effects on capsicum, the sequence was [BF4]- > [TF2N]- > [PF6]-. These findings provide a theoretical reference for the next step in the synthesis and the use of green ionic liquids.

Ni-Catalyzed Redox-Neutral Ring-Opening/Radical Addition/Ring-Closing Cascade of Cycloketone Oxime Esters and Vinyl Azides.

A nickel-catalyzed iminyl radical-triggered C-C bond cleavage/radical addition/cyclization cascade of oxime esters and vinyl azides is described. This protocol enables rapid access to the cyanoalkylated 3,4-dihydro-2 H-pyrroles and phenanthridines in good yields via adjustment of the substrate's properties. Moreover, these reactions proceed under mild and redox-neutral conditions with a board substrate scope and excellent functional group tolerance.

Brønsted-Acid-Catalyzed Synthesis of 3-Alkoxy and 3-Sulfamido Indanones via a Tandem Cyclization.

Brønsted-acid-catalyzed allylic substitution reactions of the in situ generated 3-hydroxy indanones with alcohols and sulfamides were investigated, which provided a facile route for the synthesis of a large variety of 3-alkoxy and 3-sulfamido indanones. The key intermediates, 3-hydroxy indanones, were obtained through the intramolecular Meyer-Schuster rearrangement of o-propargyl alcohol benzaldehydes. The resulting 3-benzyloxy indanone could be selectively modified by allylic sulfonamidation and reduction reactions.

K2S2O8/TEMPO-Induced Cascade Oxidative Cyclization/1,2-Migration of Electron-Deficient Groups: Strategy for the Construction of 1 H-Pyrrol-2(3 H)-ones.

A K2S2O8/TEMPO-induced oxidative cyclization of N-unprotected enaminoesters and enaminones that gave 1 H-pyrrol-2(3 H)-ones in good yields with broad functional group compatibility is reported. This method provides easy access to 1,2-carbon migration of ester or acyl group under transition-metal-free conditions.

KI-catalyzed oxidative cyclization of α-keto acids and 2-hydrazinopyridines: efficient one-pot synthesis of 1,2,4-triazolo[4,3-a]pyridines.

A one-pot approach to substituted 1,2,4-triazolo[4,3-a]pyridines has been developed that is based on a KI-catalyzed oxidative cyclization of α-keto acids and 2-hydrazinopyridines. This transition-metal-free procedure was highly efficient and shows good economical and environmental advantages.

Synthesis of Substituted 2-Amino-1,3-oxazoles via Copper-Catalyzed Oxidative Cyclization of Enamines and N,N-Dialkyl Formamides.

A facile synthesis of 2-amino-1,3-oxazoles via CuI -catalyzed oxidative cyclization of enamines and N,N-dialkyl formamides has been developed. The reaction proceeds through an oxidative C-N bond formation, followed by an intramolecular C(sp2 )-H bond functionalization/C-O cyclization in one pot. This protocol provides direct access to useful 2-amino-1,3-oxazoles and features protecting-group-free nitrogen sources, readily available starting materials, a broad substrate scope and mild reaction conditions.

Synthesis of Polycarbonyl Pyrroles via K2S2O8-Mediated Oxidative Cyclization of Enamines.

A novel K2S2O8-promoted oxidative cyclization of enamines is described. A variety of enamines having diverse functional groups and substitution patterns react well using K2S2O8 as the oxidant in the absence of catalyst. This protocol provides a very simple route for the synthesis of polycarbonyl pyrroles and has the advantages of readily available starting materials, mild reaction conditions, and a wide scope of substrates.

Regioselective Intermolecular [2 + 2]-Cycloaddition of α-Iodo-Unsaturated Ketones Promoted by Diisobutylaluminum Hydride.

The development of intermolecular [2 + 2]-cycloaddition of α-iodo-unsaturated ketones in the presence of diisobutylaluminum hydride (Dibal-H) is reported to produce various trispirocyclic derivatives containing a cyclobutane ring. This sequential lactonization/[2 + 2]-cycloaddition proceeds in high regioselectivity under mild conditions.

Thermoreversible gel lubricants through universal supramolecular assembly of a nonionic surfactant in a variety of base lubricating liquids.

The present paper investigates a new type of thermoreversible gel lubricant obtained by supramolecular assembly of low-molecular-weight organic gelator (LMWG) in different base oils. The LMWG is a nonionic surfactant with polar headgroup and hydrophobic tail that can self-assemble through collective noncovalent intermolecular interactions (H-bonding, hydrophobic interaction) to form fibrous structures and trap base oils (mineral oils, synthetic oils, and water) in the as-formed cavities. The gel lubricants are fully thermoreversible upon heating-up and cooling down and exhibit thixotropic characteristics. This makes them semisolid lubricants, but they behave like oils. The tribological test results disclosed that the LMWG could also effectively reduce friction and wear of sliding pairs compared with base oils without gelator. It is expected that when being used in oil-lubricated components, such as gear, rolling bearing, and so on, gel lubricant may effectively avoid base oil leak and evaporation loss and so is a benefit to operation and lubrication failure for a long time.

Laxative inspired ionic liquid lubricants with good detergency and no corrosion.

1-Alkyl-3-methylimidazolium bis(2-ethylhexyl)sulfosuccinate (L-DOSS10n, n = 2, 4, 8) ionic liquids (ILs) were synthesized from dioctyl sodium sulfosuccinate (NaDOSS), which is a cheap, bulk available laxative medicine used for the treatment of constipation. The ILs showed lower corrosion levels and higher hydrolysis stabilities than conventional ILs such as 1-butyl-3-methyl imidazolium tetrafluoroborate (L-B104) and 1-butyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)imide (L-F104) due to their halogen-free characteristic. The tribological properties of the ILs were also better than those of L-B104 and L-F104 for various contacts. Thus, they can be used as replacements for conventional IL lubricants, which may solve the problems of corrosion and high cost to put conventional IL lubricants into industrial application. Coking test results indicated that the synthesized ILs have high deterging ability. Thus, these ILs may be used as lubricants that restrain carbonaceous deposition as well as oil sludge and varnish formation on the metal contacts during the sliding process. Moreover, the synthesized ILs can disperse, loosen, and remove the already formed harmful substances and keep the metal contacts clean.

In situ formed ionic liquids in synthetic esters for significantly improved lubrication.

A novel way of in situ forming ionic liquids (ILs) in synthetic esters is presented. Lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) can form ILs with synthetic esters, [Li(synthetic ester)]TFSI, by the donation of lone pairs on carbonyl oxygen atoms of an ester molecule to a lithium ion to form a weakly Lewis-acidic complex cation [Li(synthetic ester)](+) and following interaction with the weakly Lewis-basic anion TFSI(-) to generate [Li(synthetic ester)]TFSI. LiTFSI has high solubility in synthetic esters because of the complex formation. The physicochemical and tribological properties of [Li(synthetic ester)]TFSI as lubricant additives were investigated. The easy preparation, extremely good solubility and excellent tribological properties of the type of ILs make them great advantages as compared with conventional ILs that can hardly be used as lubricant additives in synthetic esters due to their low solubility. The lubrication mechanism of these ILs is tentatively discussed.

Design and regioselective synthesis of a new generation of targeted therapeutics. Part 3: Folate conjugates of aminopterin hydrazide for the treatment of inflammation.

Efficient syntheses of folate receptor (FR) targeting conjugates of the anti-inflammatory, aminopterin hydrazide, are described. 2-{4-Benzoylamino}-5-oxo-5-{N'-[2-(pyridin-2-yldisulfanyl)-ethoxycarbonyl]-hydrazino}-pentanoic acid is synthesized from commercially available 4-[(2-amino-4-imino-3,4-dihydro-pteridin-6-yl-methyl)-amino]-benzoic acid. Conjugation of this novel, activated aminopterin hydrazide to folic acid through cysteine-terminating (C-terminus), peptide/carbohydrate spacers results in highly water soluble conjugates which allow for the release of free aminopterin hydrazide within the endosomes of targeted cells.

Properties influencing the relative binding affinity of pteroate derivatives and drug conjugates thereof to the folate receptor.

PURPOSE: Using in vitro competition assays, determine salient chemical features of pteroates and pteroate-drug conjugates which afford high affinity to the folate receptor. MATERIALS AND METHODS: Both folate binding protein-coated polystyrene plates and adherent human cell-based assays were used to evaluate the effects of assay temperature and buffer composition on pteroate/pteroate-drug conjugate binding affinity. Following assay selection and optimization, the relative binding affinities of ten vitamers and derivatives as well as seven pteroate-drug conjugates were evaluated. RESULTS: Compared to polystyrene plates containing immobilized folate binding protein, adherent KB cells were determined to be an equally effective, more desirable source of folate receptor for such analyses. Using the latter method, we discovered that a charged group positioned in close proximity to the pteroate's aryl moiety is critical for retaining high binding affinity. We also found that a diverse set of bioactive small molecule agents can be attached to folic acid in a manner that does not appreciably disturb this vitamin's intrinsic high affinity for the folate receptor. However, conjugation of lipophilic, high protein-binding agents to folate was sometimes found to dramatically reduce affinity, which is a finding that best exemplifies the need for having a reliable in vitro assay for determining a compound's RA. CONCLUSION: Molecules which bind best to the human folate receptor are those that contain hydrophilic regions distal to the ligand's aryl group, and for drug conjugates, an extended hydrophilic spacer placed in-between the pteroate and drug cargo moieties.

Folate-targeted dinitrophenyl hapten immunotherapy: effect of linker chemistry on antitumor activity and allergic potential.

Targeting of malignancies with folate-linked therapeutics has proven to be a promising endeavor due to the preferential expression of folate receptors (FR) on human tumors. We have shown that folic acid (pteroyl-glutamate) can be used to deliver an antigenic hapten, fluorescein, to the surface of tumor cells to promote their opsonization within a fluorescein-immunized host. Here, we investigate structure-activity relationships among members of another class of folate-hapten conjugates ( EC57, EC63, EC0293, and EC0294), namely, those containing the dinitrophenyl (DNP) group as the antigenic hapten. We report that despite exhibiting similar affinities for the FR, the antitumor activity and allergic potential of these DNP conjugates varied depending on their linker chemistries and abilities to bind anti-DNP IgG/IgE antibodies. Unlike EC57 and EC63, both EC0293 and EC0294 (i) share the identical DNP bridging chemistry to that found in keyhole limpet hemocyanin (KLH)-DNP (i.e., the immunogen), (ii) efficiently recognize DNP-specific IgG, and (iii) mediate more pronounced antitumor responses. However, EC0293 and EC0294 were also found to recognize DNP-specific IgE, and they displayed a greater risk of allergy when evaluated in a passive cutaneous anaphylaxis assay. Nonetheless, upon co-stimulation with the appropriate cytokines (IL-2/IFN-alpha), the folate-targeted "haptenization" process allowed for tumor rejection and protective antitumor immunity without causing any visible allergy in immunized mice. Our data further support the concept that folate-hapten-targeted immunotherapy may offer an effective therapeutic option for treatment of FR-positive cancers, but such treatment should proceed with caution given the risk of a potential allergic reaction.

DABCO-catalyzed reaction of alpha-halo carbonyl compounds with dimethyl acetylenedicarboxylate: a novel method for the preparation of polysubstituted furans and highly functionalized 2H-pyrans.

[Chemical reaction: see text] Polysubstituted furans and highly functionalized 2H-pyrans were prepared in good yields by DABCO-catalyzed reactions of alpha-halo carbonyl compounds with dimethyl acetylenedicarboxylate (DMAD) at room temperature.