Highly enantioselective synthesis of cyclopropylphosphonates catalyzed by chiral ruthenium porphyrins

[reaction: see text] The asymmetric addition of diisopropyl diazomethylphosphonate to styrene derivatives was carried out by using chiral ruthenium porphyrins as catalysts. The reaction proceeded under mild conditions and gave trans-cyclopropylphosphonates with good yields and high ee's (up to 92%). A progressive increase for stereochemical effectiveness exists between enantiomeric excess and the number of chiral goups linked to ruthenium porphyrins.     

Trianglamine as a new chiral shift reagent for secondary alcohols

Chiral trianglamines 1 and 2 were found to be useful as NMR chiral shift reagents for the determination of enantiomeric purity and absolute configuration of several kinds of secondary alcohols, cyanohydrins, and propargyl alcohols.     

New macrocyclic compound as chiral shift reagent for carboxylic acids

[structure: see text] We have prepared a novel chiral macrocyclic compound 3 from a C2-symmetric aminonaphthol in a high yield. Enantiomeric acids have large nonequivalent chemical shifts (up to 0.80 ppm) in the presence of 3 in 1H NMR (500 MHz) spectra. Quantitative analyses of a series of mandelic acids with different enantiomeric purities show that host 3 is an excellent chemical shift reagent for chiral carboxylic acids.     

Efficient NMR chiral discrimination of carboxylic acids using rhombamine macrocycles as chiral shift reagent

Chiral rhombamine macrocycles 1a-b were prepared by a [2+2]cyclocondensation reaction of (R,R)-1,2-diaminocyclohexane with corresponding dialdehydes and were found to be useful as NMR chiral shift reagents for the determination of enantiomeric purity and the absolute configuration of a wide range of carboxylic acid and amino acid derivatives.     

Coordination-induced branched self-assembly of porphyrins bearing two redox-active phenylenediamine chains

The porphyrins bearing two three-dimensionally regulated oligoaniline chains with terminal pyridyl groups were synthesized. The self-assembled branched polymer complex by introducing Zn(II) to the porphyrin was achieved in solution, which underwent dropcasting on the surface of mica to result in dome-like nanostructures.     

Synthesis of a water-soluble chiral NMR shift reagent: (S)-PDTA

A five-step synthesis of the water-soluble chiral polydentate ligand, (S)-PDTA [(S)-PDTA = N,N,N′,N′-tetrakis[(hydroxycarbonyl)methyl]-(S)-1,2-diaminopropane] starting from l-alanine has been worked out, via steps with retention of chirality. Total yield is 50.7% (average of ～88% for each step), while published methods report 33.4% total yield over four steps.     

A simple chiral shift reagent for measurement of enantiomeric excesses of phosphine oxides

(R)-(?)-N-(3,5-dinitrobenzoyl)-α-phenylethylamine is a chiral shift reagent which allows ee measurements of various phosphine oxides. Good results were obtained for monophosphine oxides with asymmetric phosphorus centers as well as with an asymmetric carbon in α position of phosphorus. The reagent is also able to differentiate the two enantiomers of racemic DIOP dioxide.     

Highly planar amphiphilic porphyrins

A first synthesis of an asymmetric and amphiphilic β-substituted porphyrin is reported. The porphyrin can be integrated into various types of nanostructures with the amphiphilic characters in hydrophilic solvents. The one-dimensional integration may induce a magnetic interaction between the central metals.     

Fast enantioselective amino acid quantitative C NMR determination by a praseodymium chiral shift reagent

The fast quantitative determination of enantiomers of amino acids by the use of a praseodymium-based water-soluble chiral shift reagent, utilizing natural abundance ¹³C NMR spectra, is described.     

A novel use of cobalt(III) meso-tetraphenylporphyrin as a chiral shift reagent

The NMR spectra of the diastereomeric complexes formed by the coordination of nitrogenous enantiomeric bases with cobalt(III) meso-tetraphenylporphyrin (CoTPP) allow the immediate differentiation of these complexes. The spectra are interpreted on the basis of symmetry (RR and SS) and pseudo-chirality (RS and SR) considerations. The effects are observed in both the proton and carbon spectra and the complexes are stable in both CDCl₃ and DMSO-d₄ solution. This technique, in principle, allows the ready determination of the optical purity of multifunctional ligands.     

Synthesis of porphyrins bearing trans-thiols

[structure: see text] A route to porphyrins bearing trans-thiols is described using a thioacetyl-containing aldehyde or a thioacetyl-containing dipyrromethane in the presence of catalytic BF3 x OEt2 followed by oxidation. Metal complexation and ammonium hydroxide induced acetyl removal provides a route to these important molecular systems for future electronics experiments in which the thiols would serve as the adhesion points to gold probes.     

Highly enantioselective asymmetric reactions involving zinc ions promoted by chiral aziridine alcohols

Enantiomerically pure, chiral secondary and tertiary aziridine alcohols (including the aziridine analogue of ProPhenol—AziPhenol) have proven to be highly effective catalysts for enantioselective asymmetric reactions in the presence of zinc ions, including arylation of aromatic aldehydes, epoxidation of chalcone and addition of diethylzinc to aldehydes, leading to the desired chiral products in high chemical yields (up to 90%) and with ee’s up to 90%. A higher catalytic activity of Prophenol-type bis(aziridine alcohol) in the aforementioned asymmetric transformations has been demonstrated.     

手性位移试剂Eu(dcm)~3的一个改进合成方法

我们对H(dcm)的Whitesides合成路线的关键步骤龙脑酰甲烷的合成和缩合反应进行了重要的改进。     

Anomalous NMR behavior of meso compounds with remote stereogenic centers on addition of chiral shift reagent or chiral solvating agent

A problem has arisen in using chiral shift reagents (CSR) and chiral solvating agents (CSA) to determine meso and racemic forms of diastereoisomers in which the stereogenic centers of the molecules are separated by achiral spacers. It is found that NMR signals of both meso and racemic forms of diastereoisomers may exhibit doubling on addition of CSR/CSA, which means that unequivocal assignments cannot be made without characterizing the effects for separate meso and racemic forms; this is particularly important for additions of CSR/CSA at relatively low concentrations, which always result in the splitting of some NMR signals of diastereoisomers. The phenomenon is demonstrated in the (31)P NMR spectra of meso and racemic forms of three spermine-bridged gem-disubstituted cyclotriphosphazatrienes, 1a-c, and compared with analogous achiral molecules, the per-substituted spermine-bridged cyclotriphosphazatrienes 2a-d. As expected, only one set of (31)P NMR signals was observed for the achiral compounds 2a-d, even on addition of CSA. Two sets of (31)P NMR ABX multiplets corresponding to meso and racemic diastereoisomers were observed for compounds 1a-c; on addition of CSA, the signals of at least one of the multiplets for each compound separated into more than the expected groups of three lines with an intensity distribution of 2:1:1. To understand this phenomenon, the meso and racemic forms of 1a and 1b and the meso form of 1c have been separated and characterized by X-ray crystallography. On addition of CSA to the racemic forms of 1a and 1b, the (31)P NMR spectrum shows the expected doubling of signals, but, unexpectedly, the same is observed for each of the meso forms of 1a-c. Analogous results using both CSA and CSR have been obtained for the meso and racemic forms of the diastereoisomeric piperazine-bridged macrocyclic-phosphazene compound, 3, whereas no effect was observed for the two meso forms of the doubly bridged macrocyclic-phosphazene compound 4. The phenomenon of doubling of the (31)P NMR signals of the meso form of singly bridged cyclotriphosphazatrienes, 1a-c and 3, is explained by consideration of the equilibrium in solution of independent complexation of a chiral ligand with molecules that have two chiral cyclophosphazene moieties separated by an achiral spacer group. The results show that the stereogenicity of such diastereoisomeric molecules in solution cannot be characterized unequivocally by NMR measurements on addition of either CSR or CSA.     

Use of a chiral praseodymium shift reagent in predicting the complete stereostructure of glisoprenin A

[structure: see text] The complete stereostructure of glisoprenin A has been predicted via analysis of the 13C NMR behaviors in the presence of (R)- and (S)-Pr(tfc)3.     

Highly sensitive colour-reaction of nickel with a new chromogenic reagent benzothiaxolyldiazoaminoazobenzene and its application

The synthesis of benzothiaxolyldiazoaminoazobenzene (BTDAB) is described, and a simple, rapid and sensitive procedure for spectrophotometric determination of nickel has been developed. At pH 9.4, in the presence of emulsifier p-octylpolyethyleneglycol phenylether (OP), the reagent reacts with nickel to form a red 1:3 (metal:ligand) complex. The nickel-BTDAB complex exhibit an adsorption maximum at 550 nm with an apparent molar absorptivity of 1.96 x 10(5) 1 mol(-1) cm(-1), Beer's law is obeyed for nickel in the range 0-7 mug per 25 ml. The proposed method has been applied to the determination of nickel in aluminum alloy with satisfactory results.     

Highly sensitive determination of enantiomeric composition of chiral acids based on aggregation-induced emission

A new chiral tetraphenylethylene derivative with the AIE effect was synthesized and showed not only high enantioselectivity for a wide range of chiral acids but also a high sensitivity of 3.0 × 10(-6) M scale. The enantiomeric purity of chiral acids could be quantitatively determined by this chiral sensor.     

Highly sensitive impedance-based propene sensor using stabilized zirconia and zinc oxide sensing-electrode

Aimed at an environmental monitoring of hydrocarbons (HCs), a new-type impedancemetric sensor was fabricated by using an yttria-stabilized zirconia (YSZ) tube and ZnO sensing-electrode (SE). The fabricated tubular sensor was examined for detection of low concentrations of propene (C₃H₆) in the presence of 1.35 vol.% H₂O and 400 ppm CO₂ at 600 °C. As a result, it was found that the present sensor could detect the low concentrations of C₃H₆ in the range of 0.05–0.8 ppm and the sensitivity varied linearly with C₃H₆ concentration. In addition, the C₃H₆ sensitivity was almost invariant with the changes in the concentration of water vapor and the interferences to other gases, such as NO₂, NO, H₂, CO and CH₄, were insignificant.     

Versatile and practical chiral shift reagent with hydrogen-bond donor/acceptor sites in a macrocyclic cavity

[structure: see text] Bifunctional macrocycle 1 with C2 symmetry was newly synthesized. NMR studies demonstrated that receptor 1 functions as a chiral shift reagent (solvating agent) that is highly effective for a wide range of chiral compounds having a carboxylic acid, oxazolidinone, lactone, alcohol, sulfoxide, sulfoximine, isocyanate, or epoxide functionality. Binding constants were determined to investigate the binding behavior of 1.     

New pincer-like receptor derived from trans-cyclopentane-1,2-diamine as a chiral shift reagent for carboxylic acids

A new pincer-like enantiopure receptor bearing two (1R,2R)-cyclopentane-1,2-diamine moieties has been synthesized and tested as a chiral shift reagent (CSR) for different carboxylic acids. This CSR is efficient for those acids bearing an aromatic group attached to Cα, especially for arylpropionic acids. A full structural study of the diastereomeric supramolecular complexes has allowed us to propose a reasonable model for the interaction.