Structural control of Schiff base ligands for selective extraction of copper(II).

Structural control of Schiff base ligands for selective extraction of copper(II) was investigated by changing pendant arms and the distance between two imine-N donor atoms in ligands. Di-Schiff base ligands, N,N'-bis(2-quinolylmethylidene)-1,2-diiminoethane (BQIE), N,N'-bis(2-pyridylmethylidene)-1,3-diimino-2,2-dimethylpropane (BPMP) and N,N'-bis(2-quinolylmethylidene)-1,3-diimino-2,2-dimethylpropane (BQMP), were used as complexation reagents for ion-pair extraction of divalent transition metal cations into nitrobenzene with picrate anion. The pendant arms affected the lipophilicity of ligand to nitrobenzene, due to their polarity. The distance between two imine-N atoms, on the contrary, was a factor of controlling the extraction selectivity. BQMP has both 2-quinolyl pendant arms and trimethylene backbone structure; use of BQMP as a complexation reagent led to the selective extraction of Cu2+ in the system.     

Complexation of N4-Tetradentate Ligands with Nd(III) and Am(III)

To improve understanding of aza-complexants in trivalent actinide?Clanthanide separations, a series of tetradentate N-donor ligands have been synthesized and their complexation of americium(III) and neodymium(III) investigated by UV?Cvisible spectrophotometry in methanolic solutions. The six pyridine/alkyl amine/imine ligands are N,N??-bis(2-methylpyridyl)-1,2-diaminoethane, N,N??-bis(2-methylpyridyl)-1,3-diaminopropane, trans-N,N-bis(2-pyridylmethyl)-1,2-diaminocyclohexane (BPMDAC), N,N??-bis(2-pyridylmethyl)piperazine, N,N??-bis-[pyridin-2-ylmethylene]ethane-1,2-diamine, and trans-N,N-bis-([pyridin-2-ylmethylene]-cyclohexane-1,2-diamine. Each ligand has two pyridine groups and two aliphatic amine/imine N-donor atoms arranged with different degrees of preorganization and structural backbone rigidity. Conditional stability constants for the complexes of Am(III) and Nd(III) by these ligands establish the selectivity patterns. The overall selectivity of Am(III) over Nd(III) is similar to that reported for the terdentate bis(dialkyltriazinyl)pyridine molecules. The cyclohexane amine derivative (BPMDAC) is the strongest complexant and shows the highest selectivity for Am(III) over Nd(III) while the imines appear to prefer a bridging arrangement between two cations. These results suggest that this series of ligands could be employed to develop an enhanced actinide(III)?Clanthanide(III) separation system.     

Di-ionizable calix[4]arene-1,2-crown-5 and -crown-6 ethers in cone conformations: synthesis and divalent metal ion extraction

Two series of di-ionizable calix[4]arene-1,2-crown-5 and -crown-6 ethers in cone conformations are synthesized. The ionizable groups are oxyacetic acid moieties and N-(X)sulfonyl oxyacetamide units with X=methyl, phenyl, 4-nitrophenyl, and trifluoromethyl, which ‘tunes’ their acidity. For competitive solvent extraction of alkaline earth metal cations from aqueous solutions into chloroform, the new ligands with N-(X)sulfonyl carbamoyl groups are efficient extractants with Ba²⁺ selectivity. On the other hand, the dicarboxylic acid analogues exhibit little selectivity in extraction of alkaline earth metal cations. For single species extractions of Pb²⁺, the ligands with both types of ionizable groups show very good extractions abilities. In single species extractions of Hg²⁺, the N-(X)sulfonyl carboxamide ligands are highly efficient, in contrast to the dicarboxylic acid compounds. Influences of the ionizable group identity, the crown ether ring size, and the presence of upper-rim p-tert-butyl groups on divalent metal ion extraction are explored.     

Chemoenzymatic preparation of optically active trans- and cis-cyclohex-4-ene-1,2-diamine and trans-6-aminocyclohex-3-enol derivatives

Lipase from Burkholderia cepacia (PSL-C) effectively catalyzed the kinetic resolution of both racemic trans-N,N-diallylcyclohex-4-ene-1,2-diamine (±)-6 and its precursor trans-6-(diallylamino)cyclohex-3-enol (±)-5. The resulting optically active vicinal diamine and β-amino alcohol were converted into a precursor of oseltamivir and a cis-cyclohex-4-ene-1,2-diamine derivative, respectively.     

Enzymatic resolution of (±)-cis- and (±)-trans-1-aminoindan-2-ol and (±)-cis- and (±)-trans-2-aminoindan-1-ol

Pseudomonas cepacia lipase (PSL) efficiently catalyses the kinetic resolution of (±)-cis- and (±)-trans-1-aminoindan-2-ol through the O-acylation reaction of the corresponding N-benzyloxycarbonyl derivative using vinyl acetate as the acyl donor. In a similar way, cis-N-Cbz-2-aminoindan-1-ol is resolved when isopropenyl acetate is used as the acylating agent. The enantioselectivity of the reaction was lower for (±)-trans-N-Cbz-2-aminoindan-1-ol due to the different steric requirements for the two conformers of this substrate.     

Obtention and characterization of a ciclesonide: methyl-beta cyclodextrin complex

Conformationally mobile, di-ionizable 1,2-dimethoxy-p-tert-butylcalix[4]arene ligands are synthesized and compared with 1,3-dimethoxyl analogues to probe the influence of regiochemistry on metal ion extraction efficiency and selectivity. Extraction of hard alkali metal and alkaline earth metal cations, intermediate Pb²⁺, and soft Hg²⁺ from aqueous solutions into chloroform are utilized to evaluate the effect of this structural variation on the ability of the ligands to complex monovalent and divalent metal ion species.     

An efficient chemoenzymatic method to prepare optically active primary-tertiary trans-cycloalkane-1,2-diamines

Optically active trans-N-Boc-cyclopentane- and cyclohexane-1,2-diamines (7) were prepared by a chemoenzymatic method from the corresponding (±)-trans-N,N-diallylcycloalkane-1,2-diamine. These mono-carbamates 7 (ee=99%) were used as the starting materials in the syntheses of different vicinal primary-tertiary diamines. Thus, by means of a simple three-step sequence involving a reductive-amination of an aromatic aldehyde with 7, N-methylation and finally, cleavage of the Boc group, several trans-N-(arylmethyl)-N-methylcyclopentane- and cyclohexane-1,2-diamines were obtained in high yields.     

PhP-PPh group bound to 1,8-positions of naphthalene: Preparation of cis isomer and synthesis of binuclear complex

A thermodynamically less stable cis isomer of 1,2-diphosphacycle was prepared from the corresponding trans isomer. Diphosphine, in which a PhP-PPh bond bridges the 1,8-positions of naphthalene, 1,2-diphenyl-1,2-dihydronaphtho[1,8-cd][1,2]diphosphole (1), was first prepared according to a previously reported method, and the trans isomer of 1 was irradiated in tetrahydrofuran with UV-vis light to reach equilibrium with cis-1 in a trans:cis ratio of 1:2. When a similar photochemical conversion was carried out using a saturated hexane solution of trans-1, cis-1 was precipitated in a good yield of 94%. The configuration of cis-1 was confirmed by X-ray analysis. Both cis- and trans-1 diphosphine ligands were used for the preparation of binuclear gold complexes. The crystal structure of (μ-cis-1)-[AuCl]₂ demonstrated that the two lone pairs of cis-1 are suitably directed for arrangement of the two gold centers in close proximity to each other. The two independent (μ-cis-1)-[AuCl]₂ molecules in the crystal were found to form a dimer through the multiple intermolecular interaction among the gold centers.     

Etude de la complexation des lanthanides trivalents par les six isomeres de l'acide diaminocyclohexanetetraacetique: Partie 1: synthèses et détermination des constantes d'acidité et des constantes de formation des complexes 1:1 avec les lanthanides trivalents de l'acide trans-1,2-diaminocyclohexane-N,N,N′,N′-tétraacétique

(Study of the complexation of trivalent lanthanides by the six isomers of diaminocyclohexanetetraacetic acid. Part 1. Syntheses, acidity constants of trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid, and formation constants of its 1:1 complexes.)The syntheses of five isomers (1,2 cis, 1,3 cis, 1,3 trans, 1,4 cis, 1,4 trans) of diaminocyclohexanetetraacetic acid which are not commercially available are described. For comparison with literature vlaues, potentiometric measurements of the acidity constants of the sixth isomer (1,2 trans) and of the stability constants of its 1:1 complexes with trivalent lanthanides are reported for an ionic strength of 1 (KCl) at 25°C. In contrast to some literature data, the stability constants found, plotted as a function of Z, display only one discontinuity at the level of gadolinium.     

Lipophilic Diamides as Ionophores for Alkali and Alkaline Earth Metal Cations

A series of lipophilic N, N, N′,N′-tetrasubstituted diamides were prepared and their selectivity in solvent polymeric membranes was studied, cis-N, N, N′, N′-Tetraisobutylcyclohexane-1,2-dicarboxamide induces a selectivity in membranes for Li⁺over alkaline earth metal cations and other alkali metal cations by a factor of about 1000 and 100 respectively. The ionophore N, N′-diheptyl-N,N′-dimethylethylmalonamide is an attractive candidate for the use in microelectrodes for the determination of intracellular Mg²⁺-activities.     

Structure of polypiperylene chain segments according to high-resolution 13C NMR spectra

The microstructure of stereoregular 1,4-trans-and 1,4-cis-polypiperylenes, as well as polymers prepared from the trans-and cis-piperylene isomers via cationic polymerization in the presence of TiCl₄, was studied by high-resolution ¹³C NMR spectroscopy. Polypiperylene synthesized through the cationic polymerization of the cis isomer had a more diversified morphology of the macromolecular chain, i.e., had higher relative amounts of 1,2-cis-units and combinations of irregular-addition 1,4-trans-units. It was shown that ¹³C NMR spectra give the most comprehensive and independent information on the details of structure of the piperylene macromolecular chain.     

Crown ether styryl dyes

New crown ether-containing styryl dyes of the benzothiazole series containing an aza-15-crown-5-ether moiety were synthesized. Thetrans-cis-photoisomerization of these dyes and their analogs was studied; the effect of metal cations on the kinetics of darkcis-trans-isomerization was elucidated. The stability constants of the complexes of thecis-isomers of these dyes with Ca(ClO₄)₂ were estimated. The dramatic increase (by more than three orders of magnitude) in the stability of the complexes on passing from a cationic dye to a betaine was attributed to the formation of an intramolecular bond in thecis-complexes between the sulfo group of theN-substituent and the metal cation located in the cavity of the azacrown-ether moiety.     

Convenient construction of a variety of glycosidic linkages using a universal glucosyl donor

This letter deals with the concept of constructing four types (cis-α, trans-α, cis-β, and trans-β) of glycosidic linkages using a universal glucosyl donor. The selectively protected universal glucosyl donor 8 was synthesized in 36% yield from d-glucose (eight steps). The donor 8 undergoes glycosidation with a primary carbohydrate alcohol 7 to give disaccharide 9 having a 1,2-cis-α-glycosidic linkage in 90% yield. The construction of the corresponding 1,2-trans-α-glycosidic linkage was performed in 68% yield (three steps) from 9. A similar glycosidation of the 2-O-(N-phenylcarbamoyl)-glucosyl donor 6 derived from 8 with 7 gave disaccharide 11 having a 1,2-trans-β-glycosidic linkage in 75% yield. The construction of the corresponding 1,2-cis-β-linkage was performed in 53% yield (three steps) from 11.     

Simple and mild stereoselective O-glycosidation using 1,2-anhydrosugars under neutral conditions

The ring opening of α-d-1,2-anhydrohexapyranoses with phenols proceeded smoothly in ethyl acetate (neutral conditions) in the absence of metal ion catalysts or additives to stereoselectively furnish 1,2-cis-α-aryl glycosides as the major product and 1,2-trans-β-aryl glycosides as the minor product in good yields. Under similar conditions, this ring opening reaction with alcohols afforded exclusively β-alkyl glycosides in excellent yields.     

Solid state N and C NMR study of dioxomolybdenum (VI) complexes of Schiff bases derived from trans-1,2-cyclohexanediamine

The ¹³C, ¹⁵N CP MAS NMR and FT-IR spectra of dioxomolybdenum (VI) complexes of trans-N,N′-bis-(R-salicylidene)-1,2-cyclohexanediamine (R=H, R=3,5-diCl, R=3,5-diBr, R=4,6-diOCH₃), trans-N,N′-bis-(2-OH-naphthylidene)-1,2-cyclohexanediamine and trans-N-(salicylidene)-N′-(2-OH-naphthylidene)-1,2-cyclohexanediamine have been measured. Comparative analysis of the NMR and IR spectra of the complexes with those of the corresponding ligands has shown that the complexation of the di-Schiff bases leads to changes in the conformation of the ligands and the charge redistribution. The asymmetric structure and non-planar structure of the complexes have been suggested.     

Copper-catalyzed one-pot N-alkenylation and N-alkylation of amides: an efficient synthesis of substituted 2,3-dihydropyrroles

A novel copper-catalyzed synthesis of substituted 2,3-dihydropyrroles via one-pot N-alkenylation and N-alkylation of amides with 1,4-diiodobut-1-ene derivatives has been developed. The reactions proceed in good to high yields using CuI as the catalyst, K₂CO₃ as the base, and rac-trans-N,N′-dimethylcyclohexane-1,2-diamine as the ligand.     

Tris-(1,2-N,N-dimethylaminomethylferrocenyl)stibine and its heterotrimetallic complex

New tertiary chloro-bis(1,2-N,N-dimethylaminomethylferrocenyl)stibine (1) and tris-(1,2-N,N-dimethylaminomethylferrocenyl)stibine ligand (2) containing CH₂NMe₂ pendenant arm at the ortho-position have been synthesized. Stibine (2) reacts with PtCl₄^2? and hetero trimetallic cis-PtCl₂L (3) complex is obtained, where stibine (2) acts as a bidentate ligand. All these compounds were characterized by various physicochemical methods and their molecular structures were determined by X-ray diffraction analyses. It is to be noted that tris(1,2-aminomethylferrocenyl)stibine represents the first example of a structurally characterized ferrocenyl pnictogen where three 1,2-disubstituted ferrocenyl groups are attached to the central antimony atom and phosphorus analogue of the stibine is missing in the literature. Stibine (1) shows a hypervalent Sb–N interaction while stibine (2) does not show this interaction in solid state.     

Dithiodiglycolamide: novel ligand with highest selectivity and extractability for palladium

A novel multidentate ligand N,N,N′,N′-tetra(2-ethylhexyl) dithiodiglycolamide DTDGA has been synthesized and studied for its extraction behavior towards various elements present in high level liquid waste (HLW). The extractant showed remarkable extractability and selectivity for palladium vis a vis other metal ions present in HLW. The distribution ratio as well as the separation factor for palladium was found to be the highest reported so far thus making this extractant one of the most promising candidates for effective separation of palladium from HLW.     

Katalytische isomerisierung von heptenen mit IrX(CO)L2

1-, 2-cis-, 2-trans-, and 3-trans-heptenes (C₇)are isomerized either very slowly or not at all with IrX(CO)L₂ at 80°C in toluene and under N₂. However, under the conditions of hydrogenation fast isomerisation takes place. With IrCl(CO)L₂ as catalyst the rate of isomerisation decreases the order: 1-C₇ ∼ 2-cis-C₇ > 3-trans-C₇ > 2-trans-C₇. This sequence is independent of the ligand L in lrCl(CO)L₂, however, with a particular isomer the rate of isomerisation is a function of L in the order L = PPh₃ > P(C₆H₁₁)3 > P(OPh)₃.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.