- Molecular palladium precursors for Pd0 nanoparticle preparation by microwave irradiation: Synthesis, structural characterization and catalytic activity
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Two new palladium complexes [Pd(MEA)2Cl2] (1) and [Pd(MEA)2Br2] (2) [MEA = (2-methoxyethyl)amine] were synthesized by the reaction of 2 equiv. of MEA with PdCl2 or [(cod)PdBr2] (cod = cyclo
- Heinrich, Frank,Kebler, Michael T.,Dohmen, Stephan,Singh, Mrityunjay,Prechtl, Martin H. G.,Mathur, Sanjay
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Read Online
- Cyclic amidine hydroiodide for the synthesis of cyclic carbonates and cyclic dithiocarbonates from carbon dioxide or carbon disulfide under mild conditions
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Hydroiodides of amidines can catalyze the reaction of carbon dioxide and epoxides under mild conditions such as ordinary pressure and ambient temperature, and the corresponding five-membered cyclic carbonates were obtained in high yields. The reaction of epoxide with carbon disulfide was also examined under the same conditions. Detailed investigation showed that the catalytic activity was highly affected by the counter anions of the amidine salts; the iodides were effective catalysts for both of the reaction of epoxide with carbon dioxide and carbon disulfide, whereas the bromide, chloride and fluoride counterparts exhibited almost no catalysis.
- Aoyagi, Naoto,Furusho, Yoshio,Endo, Takeshi
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supporting information
(2019/12/09)
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- Palladium-Catalyzed Hydride Addition/C-H Bond Activation Cascade: Cycloisomerization of 1,6-Diynes
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The use of ammonium halide salts as metal hydride precursors in a new Pd-catalyzed cycloisomerization of 1,6-diynes, which affords unexplored silylated 2-azafluorenes, is reported. This cascade process includes the addition of a Pd-hydride species to a π-system, intramolecular carbopalladation, and C(sp2)-H bond activation. A variety of functional groups are tolerated, and the synthetic utility of the resulting products has been demonstrated by a series of derivatizations.
- Rodríguez, José F.,Burton, Katherine I.,Franzoni, Ivan,Petrone, David A.,Scheipers, Ina,Lautens, Mark
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supporting information
p. 6915 - 6919
(2018/11/21)
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- Deciphering a 20-Year-Old Conundrum: The Mechanisms of Reduction by the Water/Amine/SmI2 Mixture
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The reaction of SmI2 with the substrates 3-methyl-2-butanone, benzyl chloride, p-cyanobenzyl chloride, and anthracene were studied in the presence of water and an amine. In all cases, the water content versus rate profile shows a maximum at around 0.2 M H2O. The rate versus amine content profile shows in all cases, except for benzyl chloride, saturation behavior, which is typical of a change in the identity of the rate-determining step. The mechanism that is in agreement with the observed data is that electron transfer occurs in the first step. With substrates that are not very electrophilic, the intermediate radical anions lose the added electron back to samarium(III) relatively quickly and the reaction cannot progress efficiently. However, in a mixture of water/amine, the amine deprotonates a molecule of water coordinated to samarium(III). The negatively charged hydroxide, which is coordinated to samarium(III), reduces its electrophilicity, and therefore, lowers the rate of back electron transfer, which allows the reaction to progress. In the case of benzyl chloride, in which electron transfer is rate determining, deprotonation by the amine is coupled to the electron-transfer step.
- Maity, Sandeepan,Hoz, Shmaryahu
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p. 18394 - 18400
(2015/12/24)
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- Synthesis and properties of arsenic(III)-reactive coumarin-appended benzothiazolines: A new approach for inorganic arsenic detection
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The EPA has established a maximum contaminant level (MCL) of 10 ppb for arsenic (As) in drinking water requiring sensitive and selective detection methodologies. To tackle this challenge, we have been active in constructing small molecules that react specifically with As3+ to furnish a new fluorescent species (termed a chemodosimeter). We report in this contribution, the synthesis and spectroscopy of two small-molecule fluorescent probes that we term ArsenoFluors (or AFs) as As-specific chemodosimeters. The AFs (AF1 and AF2) incorporate a coumarin fluorescent reporter coupled with an As-reactive benzothiazoline functional group. AFs react with As3+ to yield the highly fluorescent coumarin-6 dye (C6) resulting in a 20-25-fold fluorescence enhancement at λem ~ 500 nm with detection limits of 0.14-0.23 ppb in tetrahydrofuran (THF) at 298 K. The AFs also react with common environmental As3+ sources such as sodium arsenite in a THF/CHES (N-cyclohexyl-2-aminoethanesulfonic acid) (1:1, pH 9, 298 K) mixture resulting in a modest fluorescence turn-ON (1.5- to 3-fold) due to the quenched nature of coumarin-6 derivatives in high polarity solvents. Bulk analysis of the reaction of the AFs with As3+ revealed that the C6 derivatives and the Schiff-base disulfide of the AFs (SB1 and SB2) are the ultimate end-products of this chemistry with the formation of C6 being the principle photoproduct responsible for the As3+-specific turn-ON. It appears that a likely species that is traversed in the reaction path is an As-hydride-ligand complex that is a putative intermediate in the proposed reaction path.
- Ezeh, Vivian C.,Harrop, Todd C.
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p. 2323 - 2334
(2013/04/10)
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- Pd-catalysed oxidative carbonylation of amino alcohols to N,N′-bis(hydroxyalkyl)ureas under mild conditions using molecular oxygen as the oxidant
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A very simple method has been developed for the selective synthesis of symmetrical N,N′-bis(hydroxyalkyl)ureas, OC[NH-(CH2)x-OH]2 (x = 3-6), by oxidative carbonylation of α,ω-amino alcohols [3-aminopropanol (3-AP), 4-aminobutanol (4-AB), 5-aminopentanol (5-APe), 6-aminohexanol (6-AH)] with CO/O2 mixtures (O2 = 5 mol%) in the presence of Pd(II)/ligand/NEt3·HI catalytic systems. The catalytic process takes place under very mild conditions (p(CO/O2) = 0.1 MPa; 303-333 K). The target products can be isolated in high yield through a very simple and straightforward procedure. The catalytic system can be easily recovered and recycled for several times. The influence of a few reaction parameters (nature of ancillary ligand and iodide co-catalyst, I/Pd molar ratio, etc.) on the catalytic activity has also been investigated and the main mechanistic features of the catalytic process fully elucidated.
- Giannoccaro, Potenzo,Ferragina, Carla,Gargano, Michele,Quaranta, Eugenio
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experimental part
p. 78 - 84
(2010/09/06)
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- Preparation of mono- and di-arylphosphines
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Mono- and di-arylphosphines are prepared by reacting an aryl compound that has a leaving group attached to a carbon atom of the aromatic ring with phosphine in the presence of a Group VIII metal catalyst.
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- Reaction of N-alkylpyredinium salts with phosphorus trichloride
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1-Alkylpyridinium bromides 1 having activated N-methylene group react with phosphorus trichloride to give N-(dichlorophosphinomethylene)pyridinium ylides 2. The site of the reaction in 1,2-dialkylpyridinium halides 3 under these conditions is determined by the relative activation of 1- and 2-methylene groups; in the absence of sufficient activation of N-methylene group, reaction occurs at the 2-methylene group to give dichlorophosphinylated anhydrobases 5 and 11. 1,4-Dialkylpyridinium bromide 13 behaves analogously to give the corresponding dichlorophosphinylated anhydrobase 14.
- Bansal, Raj K.,Gupta, Neelima,Gupta, Rakhi,Pandey, Garima,Agarwal, Mamta
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p. 121 - 130
(2007/10/03)
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- AMINOLYSIS OF VINYLAMMONIUM SALTS. EFFECTS OF STRUCTURE AND MEDIUM
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The kinetics of the aminolysis of a series of vinylammonium salts ZCH=CHN+R3*X- were investigated in polar solvents and in water at 25 deg C.A quantitative assessment was made of the effect of the nature of the medium and the structure of activating group Z on the rate of the investigated processes.The aminolysis rate of the salts increases with increase in the donating characteristics of the solvent on account of the greater stabilization of the transition state compared with the initial state.Increase in the accepting characteristics of the medium leads to retardation of the process as a result of increase in the electrophilic solvation of the amine in the initial state.
- Kravchenko, V. V.,Popov, A. F.,Kotenko, A. A.
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p. 1332 - 1336
(2007/10/02)
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- Ethynylthiophenoxy derivatives of diphenylhexafluoropropane
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Ethynylphenyl derivatives of diphenylhexafluoropropane having the formula: STR1 where X is oxygen or sulfur and each of R, R1, or R2 is hydrogen or ethynyl. The compounds are useful in forming polymer structures, either homopolymers or copolymers.
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- REACTIVITY OF CONJUGATED BASES OF HYDRIDOPHOSPHORANES. SYNTHESIS OF UNUSUAL PHOSPHORANES BEARING P-S(-), P-Se(-), P-P-S(-) AND P-N- AS EXOCYCLIC BONDS
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Triethylammonium salts of spirophosphoranes having P-SH, P-SeH, P-P-SH and P-NH- bonds were prepared by reaction, in presence of triethylamine, of hydridophosphoranes on sulfur, selenium, Lawesson's reagent, tosylazide.With trimethylchlorosilane, trico-ordinated compounds was obtained instead of pentaco-ordinated derivatives.
- Lamande, Lydia,Munoz, Aurelio,Garrigues, Bernard
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p. 181 - 184
(2007/10/02)
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- Infrared Spectroscopic Studies of Hydrogen Bonding in Triethylammonium Slats. Part 4. Rearrangement of Hydrogen-bonded Ion Pairs of Triethylammonium Salts caused by Interaction with Tetrabutylammonium Salts in Solution
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Rearrangement of triethyl- and tetrabutylammonium salts in chloroform solution has been revealed from the characteristic features of the ν(N+H) bands caused by Fermi resonance interaction.Temperature changes of the i.r. spectra show this process to be reversible.Rearrangement constant K1 and K-1 and enthalpies -ΔH (for some cases only) of this process have been determined by measuring the total integrated intensities of the ν(N+H) bands of complexes which are in equilibrium.K1 values of the tetrabutylammonium salts increase with decreasing hydrogen bonding strength in triethylammonium salts.The measured enthalpies of rearrangement and those calculated from the ν(N+H) bands of hydrogen-bonded complexes studied are in agreement.It has also been shown that tetrabutylammonium salts anions can participate in the rearrangement of hydrogen-bonded ion pairs like the organic bases studied previously.
- Mashkovsky, Alexander A.,Nabiullin, Ahat A.,Odinokov, Stanislav E.
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p. 1879 - 1884
(2007/10/02)
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- 1,2-Halohydrincarboxylic acid esters and a process for their preparation
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1,2-Halohydrincarboxylic acid esters of the formula STR1 wherein R1, R2, R3, and R4 are identical or different and represent hydrogen, cyano and optionally substituted alkyl, alkenyl, aralkyl, aryl, alkoxycarbonyl, acyloxy, alkoxy and aryloxy, and furthermore R1 and R2 and/or R3 and R4, or R1 and R3 and/or R2 and R4 can be linked, forming a ring with the carbon atoms to which they are bonded; R5 represents hydrogen and optionally substituted alkyl, alkenyl, aralkyl, aryl, alkoxy and alkoxycarbonyl and X represents fluorine, chlorine, bromine and iodine; a process for preparing such 1,2-halohydrincarboxylic acid esters by reacting a cyclobutane-cis-1,2-diol of the formula STR2 with an orthoester of the formula STR3 wherein R1 -R5 have the previously ascribed significance and R6 -R8 are identical or different and represent optionally substituted alkyl, alkenyl, aralkyl and aryl, (or a ketene-acetal corresponding thereto) to give a 1,3-dioxolane and reacting the resultant 1,3-dioxolane with a halogenosilane or an acid halide. Also disclosed is a process for preparing compounds of the formula STR4 by contacting a 1,2-halohydrin ester of the formula given above with a base suitably at a temperature of 20° to 150° C.
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- Polymonoolefin quaternary ammonium salts of triethylenediamine
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High molecular weight N-hydrocarbyl-substituted quaternary ammonium salts in which the hydrocarbyl group has a molecular weight of from about 350-3000 such as a polybutene ammonium chloride are effective detergents and dispersants for gasoline and lubricating oils.
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- Lubricant additive
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High molecular weight N-hydrocarbyl-substituted quaternary ammonium salts in which the hydrocarbyl group has a molecular weight of from about 350-3000 such as a polybutene ammonium chloride are effective detergents and dispersants for gasoline and lubricating oils.
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- Boron-nitrogen compounds. XXXIV. Preparation and some properties of 2-halo-1,3,2-diazaboracycloalkanes
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A series of 2-halo-1,3,2-diazaboracycloalkanes has been prepared by (a) the interaction of trialkylamine-trihaloboranes with alphatic α,ω-diamines, (b) displacement of dimethylamino groups of 2-dimethylamino-1,3,2-diazaboracycloalkanes with halogen through interaction with boron trihalides, and (c) a transhalogenation reaction. The 2-halo-1,3,2-diazaboracycloalkanes are thermally rather stable but are very reactive toward moisture and oxygen. The boron-bonded halogen is readily replaced by organic groups through interaction with Grignard reagents. All compounds have a characteristic BN absorption in the 1510-1540-cm-1 region of their infrared spectra and the proton magnetic resonance spectra are consistent with their structure. In the mass spectra, the parent peaks P+ are generally less abundant than the (P - 1)+ peaks.
- Wang, Tai-Tzer,Busse, Paul J.,Niedenzu, Kurt
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p. 2150 - 2152
(2008/10/08)
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