Search results for "Phosphine"
showing 10 items of 618 documents
Allylester als selektiv abspaltbare Carboxyschutzgruppen in der Peptid- undN-Glycopeptidsynthese
1983
Allylester eignen sich als Schutz der Carboxyfunktion bei Peptid- und N-Glycopeptidsynthesen und konnen von Aminosauren einfach hergestellt werden. Unter den Bedingungen der Boc- und Z-Gruppenabspaltung im Sauren sind die Allylester bestandig. Durch Behandlung mit katalytischen Mengen von Tris(triphenylphosphan)rhodium(I)-chlorid in Ethanol/wasser (9:1) werden sie im neutralen bis schwach basischen Milieu schonend gespalten. Der N-terminale Schutz und die N-glycosidische Bindung bleiben dabei unverandert erhalten. Die dadurch mogliche selektive Deblockierung der α-Carboxyfunktion geschutzter N-glycosylierter Asparagin-Derivate 15 wird zur gezielten C-terminalen Kettenverlangerung zu N-Glyco…
1970
Two mechanisms are feasible in the anionic polymerization of virtually anhydrous formaldehyde initiated by uncharged LEWIS-bases such as tertiary amines and phosphines: 1. Direct initiation with formation of macrozwitterions the conventional mechanism in which an impurity such as water or methylene glycol acts as a cocatalyst. The investigations were carried out mainly by end group analysis. With triethyl amine as initiator the cocatalysis mechanism is the only or, at least, the predominant mechanism (at 20°C in dimethyl formamide). Quaternary ammonium ions – if any – are present in concentrations much below the concentrations of anionic chain ends. The latter were determined by termination…
Competitive and Selective Csp3Br versus Csp2Br Bond Activation in Palladium-Catalysed Suzuki Cross-Coupling: An Experimental and Theoretical Study …
2010
Phosphine ligands have been demonstrated to have an effect on reactivity and selectivity in the competitive intramolecular palladium-catalysed Suzuki-Miyaura coupling of dibromo sulfoxide 1a possessing two different hybridised electrophilic carbons. It was found that the bromine bond to the sp(3)-hybridised carbon is selectively replaced in the presence of unhindered phosphines such as PPh(3) or xantphos. The use of hindered phosphine ligands such as P(o-tol)(3) and P(1-naphthyl)(3) reversed the selectivity, conducting the cross-coupling at the Csp(2)-Br. Identical trends were observed in external competition experiments carried out with bromomethyl sulfoxide and different substituted bromo…
Amine functionalized ZrO2 nanoparticles as biocompatible and luminescent probes for ligand specific cellular imaging
2015
Surface functionalized ZrO2 nanoparticles show strong photoluminescence and are a versatile tool for cellular targeting due to their chemical functionality. They are highly photostable, biocompatible and amenable to coupling with bioligands (e.g. secondary goat anti-rabbit antibody (GAR) and tri-phenyl phosphine (TPP)) via carbodiimide chemistry. Antibody (GAR) functionalized ZrO2 nanoparticles were used to image the nuclear protein Sirt6, whereas triphenyl phosphonium ion (TPP) functionalized ZrO2 nanoparticles specifically targeted the mitochondria. The versatility and easiness of the ZrO2 surface modification opens up new possibilities for designing non-toxic water dispersible and photos…
CCDC 2074194: Experimental Crystal Structure Determination
2022
Related Article: Charline Sire, Hélène Cattey, Anthonia Tsivery, Jean‐Cyrille Hierso, Julien Roger|2022|Adv.Synth.Catal.|364|440|doi:10.1002/adsc.202101211
Stereoselective synthesis of o-bromo (or iodo)aryl P-chirogenic phosphines based on aryne chemistry.
2012
The efficient synthesis of chiral or achiral tertiary phosphines bearing an o-bromo (or iodo)aryl substituent is described. The key step of this synthesis is based on the reaction of a secondary phosphine borane with the 1,2-dibromo (or diiodo)arene, owing to the formation in situ of an aryne species in the presence of n-butyllithium. When P-chirogenic secondary phosphine boranes were used, the corresponding o-halogeno-arylphosphine boranes were obtained without racemization in moderate to good yields and with ee up to 99%. The stereochemistry of the reaction, with complete retention of the configuration at the P atom, has been established by X-ray structures of P-chirogenic o-halogenopheny…
Vibrational Spectrum of Phosphine Molecule
2004
Coumarin-Phosphine-Based Smart Probes for Tracking Biologically Relevant Metal Complexes: From Theoretical to Biological Investigations
2016
International audience; Ten metal-based complexes and associated ligands have been synthesized and characterized. One of the metal ligands is a coumarin-phosphine derivative, which displays tunable fluorescence properties. The fluorescence is quenched in the case of the free ligand and ruthenium and osmium complexes, whereas it is strong for the gold complexes and phosphonium derivatives. These trends were rationalized by theoretical calculations, which revealed non-radiative channels involving a dark state for the free ligands that is lower in energy than the emissive state and is responsible for the quenching of fluorescence. For the Ru-II and Os-II complexes, other non-radiative channels…
α-Aminophosphonates, Phosphinates, and Phosphine Oxides as Extraction and Precipitation Agents for Rare Earth Metals, Thorium, and Uranium : A Review
2022
α-Aminophosphonates, -phosphinates, and -phosphine oxides are a group of organophosphorus compounds that were investigated as extraction agents for rare earth (RE) metals and actinoids for the first time in the 1960s. However, more systematic investigations of their extraction properties towards REs and actinoids were not started until the 2010s. Indeed, recent studies have shown that these α-amino-functionalized compounds can outperform the commercial organophosphorus extraction agents in RE separations. They have also proven to be very efficient extraction and precipitation agents for recovering Th and U from RE concentrates. These actinoids coexist with REs in some of the commercially im…
CCDC 139658: Experimental Crystal Structure Determination
2001
Related Article: P.Lahuerta, E.Moreno, A.Monge, G.Muller, J.Perez-Prieto, M.Sanau, S.-E.Stiriba|2000|Eur.J.Inorg.Chem.||2481|doi:10.1002/1099-0682(200012)2000:12<2481::AID-EJIC2481>3.0.CO;2-M