Influence of crown ethers on thermal decarboxylation of salts of perfluorocarboxylic acids

Thermal decarboxylation of potassium salts of perfluorocarboxylic acids in the presence of 20 mole % of crown ethers takes place in 1 h at 180°C and gives internal perfluoroolefins in yields of up to 95%. The predominance in product mixtures of isomers whose double bond is adjacent to the trifluoromethyl group is associated with kinetic control of the reaction. The kinetic parameters of the process have been found and the relative activities of a series of crown ethers have been established. A scheme is advanced to show their influence on the reaction studied.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2259–2261, October, 1991.     

Luminescence of lanthanides in complexes with chromophoric crown ethers

Spectral luminescence characteristics, viz., quantum yields and luminescence lifetime, of the Yb³⁺ and Nd³⁺ ions in aqueous-methanolic solutions of their complexes with chromophoric benzo-15-crown-5 derivatives were determined. The efficient 4f-luminescence (_exc = 337 nm) is due to the intramolecular transfer of the excitation energy from the chromophoric moiety of the molecule to the Ln³⁺ ion.     

Periphery-modified crown ethers. Synthesis of bis-5,8-dimethoxy-1,4-methanonaphthalene-fused crown ethers

The easily accessible and multi-functionalized 5,8-dimethoxy-6,7-dihydroxy methyl-1,4-dihydro-1,4-methanonaphthalene (1) has been utilized as the basic building material to synthesize the symmetric bis-methanonaphthalene-fused crown ethers 14a-d (BMN-16-crown-4, BMN-22-crown-6, BMN-28-crown-8, and BMN-34-crown-10), that are constructed based on the connection between the α,β-bis-benzylic carbon atoms of diol 1 and oligoethylene glycols (9a-d) via two synthetic routes keyed upon the method of Williamson ether synthesis.     

Synthesis and complex-forming properties of crown ethers incorporating glucuronic acid moieties

Crown ethers1 and4 of the 18-crown-6 type containing two glucose units have been oxidised by KMnO₄ into mono- and dicarboxylic acid derivatives (5 and11), and derivatives with different lipophilicities of the above crown ethers, namely the acetyl, benzyl and butyl derivatives (8–10, 13, 14) and methyl esters (6 and12) have been synthesizedThe association constants (K _a) with Li, Na, K and NH₄ cations measured in CHCl₃ indicate that complexing ability increases on introduction of carboxy groups, and selectivity changes in favour of the Na cation. These compounds were able to transport alkyl-ammonium salts through a CHCl₃ liquid membrane, displaying, however, no chiral recognition ability.     

Cotrimerization of mono- and dinitriles of perfluorocarboxylic acids under high pressures

Cotrimerization of mono- and dinitriles of perfluorocarboxylic acids under high pressures affords oligoperfluoroalkylenetriazines. These oligomers are highly efficient stabilizers of thermooxidative destruction of perfluoropolyethers, when they are contacting with metals at elevated temperatures.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1814–1816, September, 1995.     

Synthesis of novel crown ethers. Part 1. Coumestan and coumestan analog derivatives of crown ethers

The presented ethylenedioxy compounds5a,5d,6a and6c are examples of novel cyclic ethers, while macrocyclic polyethers represent new crown ether analogues. New coumestan-crowns5a-f, derivatives of 6,7-dihydroxy-3,4-dihydro-2H-dibenzofuran-1-one and 6,7-dihydroxy-3,3-dimethyl-3,4-dihydro-2H-dibenzofuran-1-one6a-e were synthesized from the correspondingo-dihydroxy compounds3a-b,4a-b and ditosylates or dichlorides of di- or triethylene glycol in the presence of K₂CO₃, in DMF/H₂O (15/1) solutions at 65–75 °C for 35 hours. The structure of the macrocyclic ethers obtained were confirmed by¹H-NMR,¹³C-NMR, IR spectra and elemental analyses.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.     

Selective lithium ion extraction with chromogenic monoaza crown ethers

Two chromogenic monoaza crown ethers were synthesized and investigated for their lithium extraction capabilities. The chromogenic monoaza 14-crown-4 compound exhibited the best selectivity for lithium over sodium; ca. 2800, with a detection limit of 0.08 ppm.     

Synthesis of chiral crown ethers derived from d-galactose and their application in enantioselective reactions

A few new α- and β-d-galactopyranoside-based chiral lariat ethers of monoaza-15-crown-5 type were synthesized. These macrocycles proved to be efficient catalysts in a few asymmetric reactions under mild phase transfer conditions. The catalytic effect of the lariat ethers with methoxy, ethoxy, isopropoxy and aryloxy substituents on the C-1 of the sugar unit in both α and β positions was compared. In the presence of β-d-galactopyranoside-based crown ethers, the asymmetric Darzens condensation of α-chloroacetophenone and benzaldehyde, the epoxidation of trans-chalcone, the cyclopropanation (MIRC reaction) of benzylidenemalononitrile and 2-benzylidene-1,3-indandione with diethyl bromomalonate were performed with enantioselectivities of 61%, 64%, 86% and 96%, respectively. In all reactions, the β-anomers were more efficient in terms of enantioselectivity than the α forms.     

Complexes of Mercury(II) Cyanide with Crown Ethers in Dimethylsulfoxide

The complexation of mercury(II) cyanide with macrocyclic ligands 15-crown-5,18-crown-6 and dibenzo-24-crown-8 in dimethylsulfoxide was studied using¹⁹⁹Hg NMR measurements. No significant complexation with 15-crown-5was observed. The stability constants K_s for 1 : 1 complexes with two other ligands were determined and found to be similar, in contrary to the results reported in nitrobenzene. Solvent effects on K_s values obtained are discussed in comparison with the literature data. X-ray crystal structure of Hg(CN)₂.A18-crown-6 was also determined.     

Diaza crown ethers bearing heterocyclic ligating groups on nitrogen atoms and their complexing properties with divalent inorganic cations

Two nitrogen-substituted 4,13-diaza-I8-crown-6 compounds, bearing 2-methylquinolyl and 2-methylquinolyl-1-oxide groups, have been prepared. Ionophore-cation selectivities with a range of inorganic divalent cations have been investigated by means of membrane techniques, demonstrating their high selectivity for the Hg(II) cation.     

Inclusion compounds: The products of the interaction of silicon,germanium and boron fluorides with crown ethers

This review deals with the problem of the interaction of Si(IV), Ge(IV) and B(III) fluorides with crown ethers and their aza analogues. The crystallographic structures have been determined of the stable products obtained by the interaction of H₂SiF₆ solution with the following crown ethers: 18-crown-6 (18C6), monoaza-18C6 (MA18C6), 1,10-diaza-18C6 (DA18C6) and 1,7-diaza-15C5 (DA 15C5). The complexes obtained are stabilized by a system of H-bonds of the O-H... O, N-H. ... O, N-H...F and O-H ... F types. For H₂GeF₆ the adducts obtained are similar to those obtained using H₂SiF₆. The crystal structures of three new boron fluoride-containing complexes with 18-membered crown ethers are also described. During macrocycle complexation the guest entities undergo chemical transformations which are stabilized by creation of the H- bond system. The results of vibrational and NMR spectra are also discussed.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.     

The supramolecular structures and reactivities of some complexes of chiral crown ethers with borane ammonia

Whereas 1 1 crystalline complexes have been isolated between borane ammonia and methyl 4,6-O-benzylidene-2,3-dideoxy--d-galactopyranosido [2,3-b]-1,4,7,10,13,16-hexaoxacyclo-octadecane (1), methyl 4,6-O-benzylidene-2,3-dideoxy--d-mannopyranosido [2,3-b] (methyl 4,6-O-benzylidene-2,3-dideoxy--d-mannopyranosido [2,3-k]-1,4,7,10,13,16-hexaoxacyclo-octadecane (3), and (1R,2R,7R,24R)-3,5,8,11,14,17,20,23,26,28-decaoxatricyclo-[21.4.0.0^2,7]octacosane (4), the hosts, methyl, 4,6-O-benzylidene-2,3-dideoxy--d-mannopyranosido[2,3-b] 1,4,7,10,13,16-hexaoxacyclo-octadecane (2) and 1,4 1,4 3,6 3,6-tetra-anhydro-2,2 5,5-bis-O-oxydiethylenedi-d-mannitol (5) have yielded 2 1 (guest:host) crystalline complexes with borane ammonia as guest. X-ray analyses of the supramolecular structures of BH₃NH₃ ·1, (BH₃NH₃)₂ ·2, BH₃NH₃ ·3, BH₃NH₃ ·4, and (BH₃NH₃)₂ ·5 have been carried out and BH₃NH₃ ·1, BH₃NH₃ ·2, and (BH₃NH₃)₂ ·5 have been shown to reduce acetophenone with enantiomeric excesses of 5, 13, and 10% respectively. Supplementary Data relating to this article (atomic coordinates of the hydrogen atoms and thermal parameters) are deposited with the British Library as Supplementary Publication No. SUP 82017 (74 pages).Dedicated to Professor H. M. Powell.     

Complex formation of alkaline-earth cations with crown ethers and cryptands in methanol solutions

The complexation of alkaline-earth cations by different crown ethers, azacrown ethers, and cryptands has been studied in methanol solutions by means of calorimetric and potentiometric titrations. The smallest monocyclic ligands examined form 21 complexes (ratio of ligand to cation) with cations which are too large to fit into the ligand cavity. With the smallest cryptand, only Sr²⁺ and Ba²⁺ ions are able to form exclusive complexes. In the case of the reaction of cryptand (211) with Ca²⁺, a separate estimation of stability constants for the formation of exclusive and inclusive complexes was possible for the first time. Higher values for stability constants are found for the reaction of alkaline-earth cations with cryptands compared to the reaction with alkali ions. This increase is only caused by favorable entropic contributions.     

冠醚酮酸和烷酸的合成

本文介绍了在PPA存在下，由B15C5和DB18C6同过量的二羧酸发生酰化作用，得到酮酸1a～e和3a～c。再把所得相应的酮酸1a～e和3a～c利用黄鸣龙法制得4'-(ω－羧基多亚甲基)苯并-15-冠-5(2a～e)和4',4'(5')-二(ω-羧基多亚甲基)二苯并-18-冠-6(4a～c)等一系列ω-冠醚酮酸。     

Influence of ligand structure and solvent effects on complexation of neutral guests by several crown ethers

The formation of complexes between crown ethers and acetonitrile, chloroform, and nitromethane were investigated in carbon tetrachloride at 25°C. A significant influence of the ring size on the selectivity of the host is evident. The host 18-crown-6 forms complexes for which the reaction enthalpy and entropy are quite high. Host molecules with benzene side groups form complexes of lower reaction enthalpy and entropy and therefore the complexes formed are less stable than that of the analogous crown ethers without aromatic groups. Solvent effects on the stability constant K, the reaction enthalpy H, and the reaction entropy S were studied for the complexation of malonitrile by 18-crown-6. The reaction enthalpy and entropy values change in accordance with the dielectric constant of the solvent used, but no overall effect on complex stability with change in solvent dielectric constant was observed.     

12-Membered crown ethers. Derivatives of benzo-and naphtho-12-crown-4 and their membrane electrode properties. Part II

A series of lipophilic derivatives of benzo-12-crown-4 and naphtho-12-crown-4 has been synthesized. The behavior of the prepared derivatives in membrane ion-selective electrodes has been studied. Selectivity changes dependent on the position and number of substituents have been observed.     

Photochromic crown ethers

An amphiphilic crown-containing styryl dye (1) was synthesized, and the effects of irradiation, temperature, and alkali and alkali-earth metal ions on the conductivity and optical spectra of its solutions in dioctyl phthalate were studied. Compound1 in thetrans-form almost completely exists as ion pairs (IP). Irradiation at a long-wavelength absorption maximum (λ_max) results in a reversible increase in the conductivity and, hence, a degree of dissociation of IP (α); these parameters decrease when complexes with metal ions are formed. The relaxation times for the photoinduced conductivity coincide with a decrease in the extinction within experimental error in the 20–60°C temperature range. The photoinduced increase in α is caused bytrans—cis-isomerization and an increase in steric hindrances for the interaction of the ClO₄ ⁻ anion with the N⁺ atom of benzothiazolium in thecis-form of1. The activation energies for the darkcis—trans-relaxation, absolute α values, and thermodynamic parameters of dissociation of IP in thetrans-form, as well as the α values in a photostationary mixture ofcis—trans-isomers, were estimated. The decrease in α after binding with metal ions is likely caused by the redistribution of the positive charge to benzothiazolium through the conjugated system of1. Correlations between the decrease in conductivity (decrease in α) and the hypsochromic shift Δλ_max after the formation of complexes between1 and metal ions were observed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1296–1301, July, 1997.     

Complexes between some lysine-containing peptides and crown ethers--electrospray ionization mass spectrometric study

The complexes between lysine-containing peptides (M) and crown ethers (CEs, 18C6, 15C5, 12C4) have been studied by the electrospray ionization (ESI) mass spectrometry. The maximum number of CEs attached has been found to be the same as that of the alkyl-amino side chains of lysine and as that of the protons attached. Examination of the breakdown plots of the abundances of the ions observed against the cone voltage (CV) has shown that mass spectrometric fragmentation pathways of [M + nH + (CE)n]+n may involve a loss of a neutral CE molecule as well as protonated one. The decrease in the CE cavity (the use of 12C4 or 15C5 instead of 18C6) leads to a dramatic lowering in the stability of the complexes in the gas phase but not in solution. Attachment of a CE to peptides increases their hydrophobicity, and therefore proceeds with lower efficiency in water than in methanol.     

Properties of monolayers of crown ethers bearing an azo and azoxy group in the macrocycle

Two methods are described for preparing monomolecular layers of crown ethers with an azo or azoxy group in the macrocycle. When the molecules used to build the monolayer are soluble in aqueous solutions, adsorptive preconcentration on mercury electrodes was used to prepare the monolayer coating. The monolayer was electroactive due to the presence of the azo or azoxy unit in the molecules. Monolayers of crown ethers bearing an azo group in the macrocycle were shown to recognize alkali metal cations present in the solution. Changes of the parameters of the voltammetric reduction peaks - peak potential and peak width, served as an indication of specific interactions of the monolayer of 13-membered and 16-membered azocrown ethers with Na⁺ and K⁺ cations, respectively.The monolayers capable of recognizing cations have also been prepared on the aqueous solution-air interface, using the Langmuir technique. In this approach, amphiphilic derivatives of the azocrowns were synthesized and the monolayer has been assembled on the subphase containing metal cations. Binding of the cation by the macrocycle has a stabilizing effect on the monolayer and higher collapse pressures are achieved than on the pure water subphase. The monolayer was transferred from the air-water interface on the solid substrate using the Langmuir-Blodgett technique. Thin mercury film electrodes on the Ag substrate, or An films evaporated on glass slides were employed as the electrode substrates. The former gave monolayer modified electrodes of higher stability.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.