Search results for "Salt"
showing 10 items of 1157 documents
Convenient Synthesis of Biologically Important Retinoids
1995
The toxic and teratogenic effects caused by the highly biologically active (all-E)-retinoic acid and its derivatives prompted us to synthesize a number of retinoids. We developed synthetic approaches to (all-E)-retinyl β-D-glucuronide 3, methyl (retinoyl β-D-glucopyranoside)uronate 5, (all-E)-retinoic acid β-D-glucopyranosyl ester 8 and (all-E)-retinoyl β-D-glucuronide 6 in high purity and yield. Compound 3 was synthesized under Koenigs-Knorr conditions from (all-E)-retinol and an α-halogenose. Compounds 5 and 8 were prepared by esterification of a silver salt of (all-E)-retinoic acid with an α-glycosyl halide in pyridine. (all-E)-Retinoyl β-D-glucuronide 6 was prepared by reaction of (all-…
Configuration of Enolates of β-Ketocarboxylic Acid Esters — Carbocation-Carbanion Salts
1996
Deprotonation of (Z)- or (E)-3-hydroxy-2,3-dimesitylpropenoic acid methyl ester (1a) with tetrakis(dimethylamino)-methane (3) led to stable salt (E)-2a, which belongs to a very rare species of salts that consist of a heteroatom-stabilized carbocation and a heteroatom-stabilized carbanion. An analogous guanidinium salt (E)-2b was formed in the reaction of 3-oxo-2,3-diphenylpropanoic acid methyl ester (1b) and 3. The molecular structures of these enolates were studied by NMR spectroscopy and an X-ray analysis of (E)-2a {MC[N(CH3)2]3} and compared with those of the corresponding alkali enolates.
Counterion's Effect on the Catalytic Activity of Zn-Prolinamide Complexes in Aldol Condensations
2012
The catalytic activity of complexes involving organic ligands and Lewis acids can be modulated by changing any of their components. In this work we have studied the influence on the stereoselectivity and catalytic activity exerted by the counterion of zinc salts employed as cocatalysts of L-prolinamide in aldol condensations. The structures of the complexes have been determined both in solution and in the solid state.
Organo-phosphorus compounds—LXVI
1970
Abstract The recemization kinetics of (+)-methyl-n-propylphenylphosphine were studied in several solvents of widely varying polarity. The recemization followed first order kinetics in every solvent with approximately equal activation energies of 30 ±3 kcal/mole. The rate of racemization showed no dependence on solvent polarity and could not be correlated with any known solvent parameters. The unusually slow racemization in caproic acid and in tributyl borate were attributed to partial salt and adduct formation respectively.
Physico-chemical investigation of nanostructures in liquid phases: Nickel chloride ionic clusters confined in sodium bis(2-ethylhexyl) sulfosuccinate…
2009
The confinement of finite amounts of nickel chloride in the hydrophilic core of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles dispersed in n-heptane has been investigated by FT-IR, UV-vis-NIR and fluorescence spectroscopies. The analysis of experimental data consistently leads to hypothesize that NiCl(2) forms small size ionic clusters stabilized by a monolayer of oriented surfactant molecules. Due to confinement and interfacial effects, these ionic clusters show peculiar photophysical properties, which are different from those possessed by the bulk material. From NiCl(2)/AOT/n-heptane solutions, by evaporation of the organic solvent, interesting salt/surfactant nanocomposi…
Bis(oxamato)palladate(II) complexes: synthesis, crystal structure and application to catalytic Suzuki reaction
2015
New bis(oxamato)palladate(II) complexes, [Pd(H2O)4][Pd(2,6-Me2pma)2]·2H2O (1), (n-Bu4N)2[Pd(2,6-Me2pma)2]·2H2O (2a), and (n-Bu4N)2[Pd(2,6-Me2pma)2]·2CHCl3 (2b) (2,6-Me2pma = N-2,6-dimethylphenyoxamate and n-Bu4N+ = tetra-n-butylammonium), have been synthesized and the structures of 1 and 2b characterized by single-crystal X-ray diffraction. Complex 1 is a double salt constituted by tetraaquapalladium(II) cations and bis(oxamato)palladate(II) anions interlinked by hydrogen bonds. The palladium(II) ions in 1 are four-coordinate with two oxygens and two nitrogens from two fully deprotonated oxamate ligands (anion), and four water molecules (cation) building centrosymmetric square-planar surrou…
Isolation of enantiomerically pure organometallic palladium compounds: synthesis of the triangles prepared from enantiopure [cis-Pd2(C6H4PPh2)2(NCCH3…
2009
Reaction of the racemic [Pd(C(6)H(4)PPh(2))Br](4) () with the silver salt of 1R-(1alpha,2beta,3alpha)]-3-methyl-2-(nitromethyl)-5-oxocyclopentaneacetate, (R)-AgO(2)CR*, results in the formation of a mixture of diastereoisomers (RRR)- and (SRR)- of the formula Pd(2)(C(6)H(4)PPh(2))(2)(O(2)CR*)(2) that were separated by standard chromatographic methods. Each diastereoisomer was readily converted into the tetrametallic stereoisomers (SS)- and (RR)-, of the formula [Pd(C(6)H(4)PPh(2))Br](4) that were isolated and characterized by X-ray crystallography. The R enantiomer of the solvated cationic species [cis-Pd(2)(C(6)H(4)PPh(2))(2)(NCCH(3))(4)](2+), obtained from (RR)-, was reacted with ammonium…
ChemInform Abstract: Reactions of the Hydrofluoroborate Salts of Open-Chain Analogues of Reissert Compounds with Some α,β-Ethylenic Esters.
2010
The reaction of the hydrofluoroborate salt of an open-chain analogue of a Reissert compound with some α,β-ethylenic esters does not give a [4 + 2] cycloadduct, as previously described in the case of ethyl acrylate. The reaction starts with a 1,3-dipolar cycloaddition of a munchnone imine 5c, d. The [3 + 2] cycloadducts 13 evolve via a rearrangement–condensation sequence to give a substituted 2-pyridone derivative 18 or 19. The proposed mechanism has been verified by the isolation and structural X-ray analysis of some compounds of the reaction sequence.
Metallic Charge‐Transfer Salts of Bis(ethylenedithio)tetrathiafulvalene with Paramagnetic Tetrachloro(oxalato)rhenate(IV) and Tris(chloranilato)ferra…
2014
The synthesis, crystal structure and physical characterization of three radical salts of the donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) and tetrachloro(oxalato)rhenate(IV) {[ReCl4(C2O4)]2–} or tris(chloranilato)ferrate(III) {[Fe(C6O4Cl2)3]3–} anions are reported. The isolated salts with ReIV are (ET)[ReCl4(C2O4)] [1, monoclinic, space group C2/c with a = 18.3409(3) A, b = 10.8414(2) A, c = 11.1285(3) A, β = 99.9714(7)°, V = 2179.38(8) A3, Z = 4] and (ET)4[ReCl4(C2O4)]·C6H5CN [2, monoclinic, space group P21/c with a = 11.8549(2) A, b = 32.9079(5) A, c = 36.4154(5) A, β = 96.742(2)°, V = 14108.1(4) A3, Z = 8]. The salt with FeIII is (ET)6[Fe(C6O4Cl2)3]·(H2O)1.5·(CH2Cl2)0.5 […
ChemInform Abstract: Solution-, Solid-Phase, and Fluorous Synthesis of β,β-Difluorinated Cyclic Quaternary α-Amino Acid Derivatives: A Comparative St…
2008
The diastereoselective synthesis of cyclic β,β-difluorinated α-amino acid derivatives bearing a quaternary stereocenter is described. The process relies on the chemo- and diastereoselective addition of allylic organometallic reagents to fluorinated α-imino esters and a subsequent ring-closing metathesis reaction (RCM). Complete selectivity in the nucleophilic addition was achieved with (R)-phenylglycinol methyl ether as a chiral auxiliary. The resulting amino acids were introduced into peptide chains, which could facilitate the preparation of potentially bioactive dipeptide derivatives. In addition, the solution synthesis of these cyclic fluorinated α-amino acids was successfully adapted to…