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11.
Afarin Moezzi Marylin M. Olmstead Doris C. Pestana Philip P. Power 《无机化学与普通化学杂志》1995,621(11):1933-1938
The reaction of either Li2PPh or Li2AsPh with the diborane(4) derivative B2(NMe2)2Br2 affords the compounds [PhP(BNMe2)2]2 ( 1 ) or [PhAs(BNMe2)2]2 ( 2 ) in good yield. Both 1 and 2 have cyclic structures featuring non-planar P2B4 or As2B4 six-membered rings which have chair configurations. Although all four borons in each ring have planar coordination, the two phosphorus or arsenic centers have different degrees of pyramidalization. Bond distances within the rings indicate that the B? B, B? P or B? As bonds are single, whereas the exo-B? N bond lengths are consistent with significant π-bonding. The ring structures of 1 and 2 are in sharp contrast to the related boron-nitrogen species (t-BuN)2N4Me4 which has a nido-N2B4 framework. The attempted synthesis of the nitrogen analogue of 1 or 2 by using a similar approach did not result in the isolation of [PhN(BNMe2)2]2, instead the tetramino diborane(4) species [B(NMe2)NHPh]2 ( 3 ), which has a structure similar to other tetramine diborane(4) compounds, was isolated. 相似文献
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14.
Franzén J Marigo M Fielenbach D Wabnitz TC Kjaersgaard A Jørgensen KA 《Journal of the American Chemical Society》2005,127(51):18296-18304
The development of a general organocatalyst for the alpha-functionalization of aldehydes, via an enamine intermediate, is presented. Based on optically active alpha,alpha-diarylprolinol silyl ethers, the scope and applications of this catalyst for the stereogenic formation of C-C, C-N, C-F, C-Br, and C-S bonds are outlined. The reactions all proceed in good to high yields and with excellent enantioselectivities. Furthermore, we will present mechanistic insight into the reaction course applying nonlinear effect studies, kinetic resolution, and computational investigations leading to an understanding of the properties of the alpha,alpha-diarylprolinol silyl ether catalysts. 相似文献
15.
Doris J. Bates Myron Rosenblum Sari B. Samuels 《Journal of organometallic chemistry》1981,209(3):C55-C59
CpFe(CO)2[C(OEt)R]BF4 complexes can be prepared by reaction of CpFe(CO)2(isobutylene)BF4 with monoalkylated acetylenes in methylene chloride/ethanol solutions. Methyl propiolate yields methyl trans-2-ethoxy-acrylate, in a reaction catalytic in CpFe(CO)2(isobutylene)BF4, and internal acetylenes can be transformed to CpFe(CO)2(vinyl ether)BF4 complexes. 相似文献
16.
The reaction of potassium-alkyl-cyanoimidodithiocarbonate 1 with α-CH-acid halo compounds to 4-aminothiazoles 3, with monochloramine to 3-amino-1,2,4-thiadiazoles 5, and with α-halocarboxylic acid anilides to 4-thiazolidinones derivatives 12 is described. Characteristics of mass- and IR-spectra of the synthesized compounds are discussed. 相似文献
17.
Augustin de Castries 《Tetrahedron》2007,63(41):10330-10336
Azamacrocycles bearing four arylsulfonyl or arylsulfinyl pendant arms have been synthesised with good yields through nucleophilic addition of 1,4,8,11-tetraazacyclotetradecane (cyclam) to phenylvinylsulfone, phenylvinylsulfoxide or (R)-tolylvinylsulfoxide in isopropanol/water media. The crystal structure of the tetraethylsulfonylphenyl substituted macrocycle has been determined by X-ray crystallography. Preliminary studies of the coordination properties of these functionalised macrocyles towards Cu(II) and Eu(III) indicate that pendant sulfoxide groups act as oxygen donor coordinating groups. 相似文献
18.
Albert Günter Herrmann und Doris Knake 《Fresenius' Journal of Analytical Chemistry》1973,266(3):196-201
Zusammenfassung Für die Bestimmung von Gesamt-, Carbonat- und Nichtcarbonat-Kohlenstoff in magmatischen, metamorphen und sedimentären Gesteinen (auch bei höheren Anteilen an organischem C) ist ein Verfahren nach dem Prinzip der coulometrischen Titration geeignet. Der Gesamt-Kohlenstoff wird ermittelt durch Erhitzung der auf <0,125 mm zerkleinerten Probe bei etwa 1250°C im Sauerstoffstrom ohne irgendwelche Zusätze. Zur Bestimmung von Nichtcarbonat-Kohlenstoff wird eine bestimmte Menge Gesteinspulver mit Salzsäure versetzt und auf einem Aluminiumblock HCl abgeraucht. Der Carbonat-Kohlenstoff entweicht als CO2. Zurück bleibt der Nichtcarbonat-Kohlenstoff, welcher wie der Gesamt-Kohlenstoff coulometrisch bestimmt wird. Der Carbonat-Kohlenstoff bzw. die äquivalente Menge CO2 ergibt sich dann aus der Differenz von Gesamt- zu Nichtcarbonat-Kohlenstoff. Das Verfahren ist anwendbar auf Kohlenstoffgehalte in Gesteinen von etwa 10 ppm bis 20 Gew.-% bei mittleren Standardabweichungen von etwa 0,0002–0,05% C (Richtwerte). Die Analysendauer für eine Probe beträgt etwa 3–5 min.
Coulometric method for the determination of total, carbonate, and non-carbonate carbon in igneous, metamorphic, and sedimentary rocks
For the measurement of total carbon the sample, ground finer than 0.125 mm and without the addition of any reagents, is ignited in a current of oxygen at about 1250°C. Non-carbonate carbon can be analysed after another portion of the sample is treated with conc, hydrochloric acid and evaporated on a hot plate; the carbonates are decomposed and the carbonate carbon is removed as carbon dioxide. The residue is non-carbonate carbon which is also determined by the coulometric method. The difference between total carbon and non-carbonate carbon corresponds to carbonate carbon or its equivalent as carbon dioxide. The method is applicable to carbon contents in rocks from 10 ppm to 20 wt.-%. The standard deviation is approximately 0.0002 to 0.05% C. Each carbon analysis takes about 3 to 5 min.相似文献
19.
Disodium salt 2 reacts with hydrogen peroxide to give 1,2,4-trithiolane 3, whereas treatment with methyl chloroformate yields 1,3-dithietane 4. Adding diluted NaOH to 3 leads to a mixture of an isothiazole 7 and 4. By chlorination of 2 isothiazole 8 is available. S-amination of 2 or 9 and following cyclization gives the isothiazoles 10 and 12, respectively. 3-Mercapto-acrylonitrile 14 reacts with quinones to condensed oxathioles 16 or 17. 相似文献
20.
Kremzow D Seidel G Lehmann CW Fürstner A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(6):1833-1853
Oxidative insertion of [Pd(PPh3)4] or [Ni(cod)2]/PPh3 into the C-Cl bond of various 2-chloroimidazolinium- and other -amidinium salts affords metal-diaminocarbene complexes in good to excellent yields. This procedure is complementary to existing methodology in which the central metal does not change its oxidation state, and therefore allows to incorporate carbene fragments that are difficult to access otherwise. The preparation of a variety of achiral as well as enantiomerically pure, chiral metal-NHC complexes (NHC = N-heterocyclic carbene) and metal complexes with acyclic diaminocarbene ligands illustrates this aspect. Furthermore it is shown that oxidative insertion also paves a way to prototype Fischer carbenes of Pd(II). Since the required starting materials are readily available from urea- or thiourea derivatives, this novel approach allows for substantial structural variations of the ligand backbone. The catalytic performance of the resulting library of nickel- and palladium-carbene complexes has been evaluated by applications to prototype Suzuki-, Heck-, and Kumada-Corriu cross-coupling reactions as well as Buchwald-Hartwig aminations. It was found that even Fischer carbenes show appreciable catalytic activity. Moreover, representative examples of all types of neutral and cationic metal-carbene complexes formed in this study have been characterized by X-ray crystallography. 相似文献