Search results for "phosphine"

Modular P-Chirogenic Phosphine-Sulfide Ligands: Clear Evidence for Both Electronic Effect and P-Chirality Driving Enantioselectivity in Palladium-Cat…

2015

Using the ephedrine methodology, modular stereoselective syntheses of a new class of P-chirogenic phosphines bearing a sulfur-chelating arm (P*,S-hybrid ligand) are described. A first series of syntheses based on a Fries-like rearrangement of P-chirogenic phosphinite-boranes, which are prepared from 2-bromobenzyl or 2-bromophenethyl alcohol and are mediated by metal–halide exchange, have been performed. This rearrangement affords phosphine-boranes stereospecifically with an o-hydroxyalkylphenyl substituent. The latter residue is subsequently converted into a sulfur-containing group. In a second series, the stereoselective syntheses were achieved according to a new strategy involving a react…

P-Chirogenic Secondary Phosphine Oxides: New Stereoselective Synthesis and Applications

2015

ortho-metallation of P(m-MeC6H4)3 in dirhodium(II) tetraacetate. Molecular structure of Rh2(O2CCH3)2[(m-MeC6H3)P(m-MeC6H4)2]2(HO2CCH3)2·CH3CO2H

1990

Abstract The thermal reaction of Rh2(O2CCH3)4(MeOH)2 and P(m-MeC6H4)3 in a 1:2 molar ratio in acetic acid yielded Rh2(O2CCH3)2[(m-MeC6H3)P(m -MeC6H4)2]2(HO2CCH3)2. Purple monoclinic crystals of this compound and one molecule of acetic acid, space group P21/c, were obtained by evaporation of a solution of the original reaction product in acetic acid/CH2Cl2 mixture. The unit cell parameters are a = 21.346(3), b = 11.909(2), c = 20.071 A, β = 97.98(1)° and Z = 4. The structure consists of a dinuclear rhodium core bridged by cisoid acetate groups and two ortho-metallated phosphine ligands. The ortho-metallation occurs at the least sterically hindered carbon atom which is trans to the methyl sub…

Unusual phosphine oxidation: new triazolopyridyl-quinolyl phosphine oxide fluorescent dyes

2015

3-(2-Pyridyl)-[1,2,3]triazolo[1,5-a]quinolylphosphines suffer an unusual phosphine oxidation due to their special geometry that allows a s-donation of the nitrogen (N1) lone pair to phosphorus. This family of compounds behaves as strong fluorophores with high quantum yields.

Complexation of phosphine ligands with peracetylated β-cyclodextrin in supercritical carbon dioxide: Effect of temperature and cosolvent on the equil…

2009

Abstract The interaction between peracetylated-β-cyclodextrin and tert-butyl and adamantyl functionalized triphenylphosphine derivatives was studied in supercritical carbon dioxide (scCO 2 ) based solvent media by UV–vis spectroscopy. The equilibrium constant for a 1:1 complexation reaction was obtained from titration spectra both in pure carbon dioxide and in the presence of methanol as a cosolvent in the temperature range 308–323 K to estimate the internal energy and entropy of the inclusion equilibrium. The values of the equilibrium constants were found significantly smaller than those obtained in aqueous solution with analogous phosphines and substantially independent of the nature of t…

Dirhodium(II) compounds with bridging thienylphosphines: studies on reversible P,C/P,S coordination.

2009

Monocyclometalated compound [Rh(2){(C(8)H(4)S)P(C(8)H(5)S)(2)}(CH(3)CO(2)H)(2)(O(2)CCH(3))(3)] (1 a) and bis-cyclometalated compound [Rh(2){(C(8)H(4)S)P(C(8)H(5)S)(2)}(2)(CH(3)CO(2)H)(2)(O(2)CCH(3))(2)] (2 a) have been isolated from the reaction of dirhodium tetraacetate and tris(2-benzo[b]thienyl)phosphine (2 BTP) using low acidic solutions. By contrast, in pure acetic acid the reaction of Rh(2)(O(2)CCH(3))(4) with 2 BTP and tris(2-thienyl)phosphine (2 TP), followed by replacement of the axial acetate ligands by chlorides, led to [Rh(2){(2-C(8)H(5)S)P(2-C(8)H(5)S)(2)}(2)Cl(2)(O(2)CCH(3))(2)] (3 b) and [Rh(2){(2-C(4)H(3)S)P(C(4)H(3)S)(2)}(2)Cl(2)(O(2)CCH(3))(2)] (5 b), respectively. These n…

Propriétés et performances de phosphines ferrocéniques dans le couplage C-O, C-S et C-N : nouvelles méthodologies de synthèse au palladium

2012

Multidentate ligands usually show great activities in low loading organometallic catalysis in palladium. Among these ligands, the use of ferrocenyl polyphosphane ligands give interesting results. Robust palladium-ferrocenyl triphosphane catalytic systems have permitted to obtain biarylamines and aryl-heteroaryl ethers in the presence of low catalytic loadings. DFT studies on catalytic cycle during formation of aryl-heteroaryl ethers were carried out. The presence of third phosphino group stabilizes a transition state which enhances the rate of the reductive elimination. Triarylamines were obtained with ferrocenyl diphosphane in the presence of 2 mol% of palladium loading. Moderate to excell…

ChemInform Abstract: Enantiocontrol in the Intermolecular Cyclopropanation Reaction Catalyzed by Dirhodium(II) Complexes with ortho-Metalated Aryl Ph…

2010

(P) and (M) dirhodium(II) complexes with ortho-metalated aryl phosphines are assessed as chiral catalysts in the enantioselective cyclopropanation of styrenes by ethyl diazoacetate; enantioselectivities up to 91% and up to 87%, respectively, for cis- and trans-2-arylcyclopropanecarboxylates are observed.

Efficient Synthesis of β-Halogeno Protected L-Alanines and Their β-Phosphonium Derivatives.

2003

Abstract Ring opening of oxazolines, prepared from l -serinates, with trimethylsilyl halides (TMSX) led to β-halogeno-N-benzoyl-α-amino esters in good to excellent yields. Quaternization of triphenylphosphine by the β-bromo or -iodo amino esters gave the corresponding β-phosphonium salts in overall yields of up to 93% and with e.e. >96%. Hydrolysis of the ester function afforded the phosphonium salt bearing an N-benzoyl-α-amino acid substituent, with partial racemization. However, the reaction of the TMSX with the carboxylic salt, prepared by saponification of the starting oxazoline ester, furnished the corresponding β-halogeno-N-benzoyl-α-amino acids in 70–95% yields. Quaternization of tri…

Embryonic Growth of Face-Center-Cubic Silver Nanoclusters Shaped in Nearly Perfect Half-Cubes and Cubes.

2016

Demonstrated herein are the preparation and crystallographic characterization of the family of fcc silver nanoclusters from Nichol’s cube to Rubik’s cube and beyond via ligand-control (thiolates and phosphines in this case). The basic building block is our previously reported fcc cluster [Ag14(SPhF2)12(PPh3)8] (1). The metal frameworks of [Ag38(SPhF2)26(PR′3)8] (22) and [Ag63(SPhF2)36(PR′3)8]+ (23), where HSPhF2 = 3,4-difluorothiophenol and R′ = alkyl/aryl, are composed of 2 × 2 = 4 and 2 × 2 × 2 = 8 metal cubes of 1, respectively. All serial clusters share similar surface structural features. The thiolate ligands cap the six faces and the 12 edges of the cube (or half cube) while the phosp…