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Showing 1 to 20 of 44 for “"isocyanates"”.
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Capillary Zone Electrophoresis Analysis of Isocyanates in Spray-Painting Operations
Various diisocyanate monomers and polyisocyanate oligomers exist in spray painting formulations and are known to be harmful to workers who are exposed to a spray-painting environment. Several methods were used for the sampling and analysis of airborne 1,6- hexamethylene diisocyanate (HDI) monomer …
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New Sampling and Analysis Method for Isocyanates in Spray-Painting Operations
… diisocyanate monomers. The measurement of isocyanates in air is a challenging sampling and analytical problem for several reasons. Isocyanates can exist in air as vapor, or as aerosol (with a wide range of particle sizes). Isocyanates are very reactive, hence, unstable. To detect …
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Intermolecular [3+2] Cycloadditions of Imino-isocyanates to Access β-Amino Carbonyl Compounds
… value in synthesis. In Chapter 1, N-isocyanates and other heterocumulenes are introduced as versatile amphoteric reagents. Their amphoteric properties are valuable in the discovery of new synthetic approaches, especially in cycloaddition reactions. While C-isocyanates are bulk …
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Microencapsulation of reactive amines and isocyanates and their application to self-healing systems
Microcapsule-based self-healing systems enable repair of crack damage in polymers and polymer matrix composites. Existing self-healing chemistries are limited by relatively weak chemical bonding between the matrix and the healing material, temperature stability, and side reactions that degrade the …
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Diastereoselectivity of the metallo-enamine condensation; addition and cyclization reactions of vinyl isocyanates
The diastereoselectivity of the metallo-enamine condensation was examined using a variety of imines and aldehydes. The highest selectivity (5:95, anti:syn) was observed in the reaction of the lithium enamine of propylidene-t-butylamine with pivaldehyde. Therefore, high diastereoselectivities can be …
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Nickel-catalyzed preparation of acrylamides from alpha olefins and isocyanates ; Synthetic studies toward ripostatin A
… reaction of a-olefins and branched aliphatic isocyanates provides c,-unsaturated amides arising from preferential C-C bond formation at the 2-position of the olefin. This sense of regioselectivity contrasts with the observed carboxamidation at the 1-position of the olefin when phosphine …
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The synthesis of perloline and some reactions of α, β unsaturated isocyanates with activated olefins / by Stephen Thomas Were
Enclosed reprints of author's articles: `A 'biogenetic like' synthesis of perloline` and `The synthesis of perloline` published in Aust. J. Chem., 1983, 36
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Preparation of benzoenyne -allenes, enyne -isocyanates and enyne -carbodiimides and their applications in the synthesis of polycyclic aromatic hydrocarbons and heterocycles
… 4,5-diarylphenanthrenes.;Thermolysis of enyne-isocyanates represents a new way of generating biradicals and/or zwitterions from unsaturated molecules having nitrogen and oxygen atom in the conjugated system. Due to the ring strain, cycloaromatization of cyclopentene-based enyne-isocyanates and …
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New methods for synthesis and modification of peptides and proteins
… and utilization of unprotected peptide isocyanates in water was developed. It was shown that easily accessible C-terminal peptide isocyanates can be conjugated to a number of strong nucleophiles in the presence of unprotected amino acid side chains for peptides and proteins of various …
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Synthesis and structure-activity relationship studies of novel anti-infectives for cross screening in tuberculosis and malaria disease models
… of diverse commercially available (sulfonyl) isocyanates, as well as the instability of isocyanates in general are drawbacks. A method that generates a vast selection of (sulfonyl) isocyanates from a range of commercially available starting materials would, hence, be very useful. A new …
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Investigations of catalyst behaviour in the formation of polyurethanes
… urethane reactions, the mechanism for aliphatic isocyanates is different to that for aromatic isocyanates. For aliphatic isocyanates, the carboxylate ligand contributes to the reaction rate in non-polar media; however this is not found in aromatic systems. The addition of carboxylic acid at low …
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Hyperbranched polyesters for polyurethane coatings: their preparation, structure and crosslinking with polyisocyanates
… microphase separation during their reaction with isocyanates, in contrast to poly-BHMPAs. The poly-BHPPA and the polyurethane networks made from them display higher Tg values than analogous poly- BHMPA compounds. Because of the high Tg of the reacting and final systems, curing must occur at …
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Part I. Cleavage of Carbamates to Isocyanates: Selectivity, Extension to the Solid Support, and Synthesis of Multivalent Glycoforms With Inter-Saccharide Carbamate Linkages. Part II. Conjugation of Carbohydrate Moieties to a Rigid Aromatic Linker for the Study of Glycoside Internal Dynamics
Part II. A synthetic protocol for the synthesis of carbohydrate-linker moieties that will allow conjugation of a saccharide to a protein is reported. This approach was demonstrated in the synthesis of the saccharide-linker moieties of the four glucopyranosyl-beta-D-glucopyranosides. The results …
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UV-initiated synthesis of novel urethane polymers
… through a photopolymerisation reaction with isocyanates has been discovered. The nitrite esters were synthesised from nitrous acid produced in situ from sodium nitrite and sulfuric or nitric acid. Yields of 79.5 and 76.4% were obtained in the synthesis of the mononitrite esters butyl- and …
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Novel N-heterocyclic activations mediated by magnesium reagents having sterically hindered ligands
… magnesiates to promote the hydroamination of isocyanates and carbodiimides, show that homoleptic [NaMg(CH2SiMe3)2] 32 can effectively catalyse at room temperature the reactions of HNPh2 with several aliphatic isocyanates to yield the relevant ureas [(NHR)C(=O)(NPh2)] (R = tBu, 29, R = Cy, 39, …
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Mild [Pd(OAc)2/PPh3] catalyzed cyclization reactions of N-Alkyl-2-vinylazetidines with heterocumulenes.
… have been acquired in reactions with isocyanates, diarylcarbodiimides, and arylisothiocyanates. Unoptimized results in reactions with ketenes and ketenimines indicate a variety of carbon electrophiles could be used for the insertion and suggest great potential for these methods in …
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Synthesis and biological evaluation of aeruginosin based compounds and self-assembly of glucosamine based compounds
… from the corresponding acid chloride and isocyanates. The self-assembling properties of these compounds were studied in several solvents, including water and aqueous solutions. Most of these compounds were found to be efficient low molecular weight hydrogelators (LMHGs) for aqueous …
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ΣΧΕΔΙΑΣΜΟΣ ΚΑΙ ΣΥΝΘΕΣΗ ΝΕΩΝ ΠΥΡΕΘΡΟΕΙΔΩΝ
… ALSO PREPARED BY THE REACTION OF THE SUITABLE ISOCYANATES (RN=C=O. R:ME,ET,ISO-PR) WITH THE OXIMES, IN ORDER TO INVESTIGATE THE VIEW THAT PYRETHROIDS MAY POSSESS CHOLINERGIC ACTION.
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Substituent Effects: A Computational Study on Stabilities of Cumulenes and Low Barrier Hydrogen Bonds
… of cumulenes-ketenes, allenes, diazomethanes and isocyanates and related systems-alkynes, nitriles and nitrile oxides is studied using the density functional theory (B3LYP, SVWN and BP86) and ab initio (HF, MP2) calculations at the 6-31G* basis set level. Using isodesmic reactions, correlation …
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Polyurethane foams containing renewable castor oil replacement
… foams are made from petroleum-based polyols and isocyanates. Due to the shortage of fossil resources, renewable biobased materials are studied as alternatives to petroleum. In this project, castor oil was chosen as a renewable biobased polyol in order to replace the nonrenewable petroleum-based …
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