Synthesis and preliminary studies on novel enantiopure crown ethers containing an alkyl diarylphosphinate or a proton-ionizable diarylphosphinic acid unit

This paper reports the synthesis, characterization and electronic circular dichroism (ECD) spectroscopic studies of a new type of crown ethers and their achiral analogues containing a tetrahedral phosphorous centre. The synthetic routes to the two chiral phosphinate derivatives [(R,R)-10 and (R,R)-11] were similar, starting from the earlier reported ethyl bis(2-hydroxyphenyl)phosphinate and the unreported methyl bis(2-hydroxyphenyl)phosphinate, respectively. The enantiopure crown ether containing phosphinic acid unit (R,R)-14 was obtained by hydrolysis of the phosphinates (R,R)-10 and (R,R)-11, respectively. ECD spectroscopy was used for investigation of the chiroptical properties as well as complex formation ability of the novel enantiopure ligands. Owing to the presence of the aryl substituents the ECD spectra are rich in bands in the ¹B_b, ¹L_a and ¹L_b regions (190-250 nm and 260-330 nm, respectively). In the case of (R,R)-14, a solvent dependent conformational behaviour was observed due to the strong dimer or aggregate forming ability of the POOH groups. This finding was supported by theoretical calculation of the monomer and the dimer forms. Phosphinates (R,R)-10 and (R,R)-11 form complexes with α-phenylethylammonium perchlorate (PEA) and α-(1-naphthyl)ethyl ammonium perchlorate (NEA) but do not discriminate between their enantiomers. All three chiral crown ethers bind strongly cations of ionic radii <∼1 Å.     

Synthesis and transport studies of new enantiopure lipophilic crown ethers containing a diarylphosphinic acid unit

The synthesis of new enantiopure lipophilic crown ethers (S,S)-6, (R,R)-6 and (S,S)-7 containing a diarylphosphinic acid unit has been carried out. The transport ability of these ligands has been studied in an aqueous source phase/lipophilic organic bulk liquid membrane/aqueous receiving phase system controlled by the pH of the media. The transport of metal ions and amines has also been studied. These studies showed high selectivity for protonated amines.     

Synthesis and enantioselective transport studies of both enantiomers of new chiral proton-ionizable crown ethers containing a diarylphosphinic acid unit

The synthesis of four new enantiopure crown ethers containing a diarylphosphinic acid unit has been carried out. As a continuation of our work in this field, the enantioselective transport ability of these ligands for chiral amines has been studied in an aqueous source phase/lipophilic organic bulk liquid membrane/aqueous receiving phase system controlled by the pH of the media. By altering the structures of the carriers we improved the enantioselectivity of the transport.     

Synthesis of crown ethers containing a thiazole subcyclic unit

Crown ethers containing a thiazole subcyclic unit are prepared from the reactions of 1,3-bis[2(4-hydroxymethylthiazoyl)]benzene with di-p-tosylates of corresponding di, tri, tetra, pentaethylene glycols in the presence of potassium hydride. However, if the cavity size in the ring system is small, [2+2] cyclization adduct also is formed.     

Chemistry of crown ethers. Synthesis of new crown ethers containing a pyridazine ring

A method for preparation of crown ethers containing a pyridazine ring based on 1,2-dihydro-3,6-dioxopyridazine was developed.     

Synthesis of new enantiopure proton-ionizable crown ethers containing a dialkylhydrogenphosphate moiety

Seven new enantiopure proton-ionizable crown ethers containing a dialkylhydrogenphosphate moiety were prepared starting from optically active dialkyl-substituted oligoethylene glycols and phosphorus oxychloride followed by mild hydrolysis of the resulting macrocyclic chlorophosphates. Pentaethylene glycols having primary hydroxyl groups gave good yields of 17-crown-6 type ethers. Pentaethylene glycols with secondary hydroxyl groups rendered about the same amount of 17-crown-6 ethers and open chain dihydrogenphosphates in low yields. Tetraethylene glycols are reluctant to undergo macrocyclization with phosphorus oxychloride, especially the ones which contain secondary hydroxyl groups.     

Synthesis of alkyl or aryl pyridazinyl ethers

This paper presents the synthesis of some alkyl or aryl pyridazinyl ethers from 2‐alkyl‐4‐halo‐5‐hydroxy‐and 2‐alkyl‐4,5‐dichloropyridazin‐3(2H)‐ones or 3,6‐dichloropyridazine. Reaction of 2‐alkyl‐4‐halo‐5‐hydroxypyridazin‐3(2H)‐ones 1 with 1,2‐dibromoethane or 1,3‐dibromopropane gave the corresponding monopyridazin‐5‐yl ethers 2 and α,ω‐[di(pyridazin‐5‐oxy)]alkanes 3 . Treatment of 4 with 4‐substituted‐phenol afforded 5‐(4‐substituted‐phenoxy)‐2‐(4‐substituted‐phenoxymethyl) derivatives 5 . Reaction of 2‐alkyl‐4,5‐dichloro derivatives 7 with 1 gave the corresponding di(pyridazin‐5‐yl) ethers 8 in good yields. Compound 10 was reacted with catechol to give monopyridazin‐3‐yl ether 11 and/or di(pyridazin‐3‐yl) ether 12 . Also we described the results for the reaction of 2‐alkyl‐4‐chloro‐5‐(4‐substituted‐phenoxy)pyridazin‐3(2H)‐ones with nucleophiles.     

Twelve-membered crown ethers: Crystal structures of benzo-12-crown-4 and naphtho-12-crown-4

The crystal structures of two 12-membered crown ethers, benzo-12-crown-4 (1) and naphtho-12-crown-4 (2), have been determined by X-ray analysis. Both structures are molecular. Compound1 is monoclonic,P2₁/b,a=8.466(3),b=8.019(3),c=33.590(10) Å, =90.99(3)^o. The unit cell contains two crystallographically independent molecules of1 with similar conformations. Compound2 is also monoclinic,P2₁/a,a=24.148(8),b=14.535(4),c=7.987(5) Å, =102.87(2)^o. Two independent molecules in the unit cell have significantly different conformations. Supplementary data relating to this publication have been deposited with the British Library as Supplementary Publication No. SUP 82145 (19 pages).     

Synthesis of lipophilic crown ethers with pendant phosphonic acid or phosphonic acid monoethyl ester groups

Synthetic routes to fifteen lipophilic crown ether phosphonic acid monoethyl esters and nine lipophilic crown ether phosphonic acids are described. For both classes of crown ethers which have pendant, protonionizable groups, the crown ether ring sizes are systematically varied from 12-crown-4 and 24-crown-8.     

Synthesis and metal ion complexation of spin labeled 18-crown-6 ethers containing an acridone or an acridine fluorophore unit

Double (spin and fluorescence) labeled pyrroline derivatives of crown ethers containing an acridone or an acridine fluorophore unit (1 and 2) and their diamagnetic analogues (3 and 4) were synthesized. Their fluorescent behavior as well as their complexation properties toward selected metal ions (Na⁺, K⁺, Mg²⁺, Ca²⁺, Zn²⁺) were examined.     

Dibenzotetraaza crown ethers: a new family of crown ethers based on o-phenylenediamine

Dibenzotetraaza (DBTA) crown ethers possess two o-phenylenediamine moieties. They are homologues of dibenzo crown ether phase-transfer catalysts and were prepared from the condensation of benzimidazoles with oligo(ethyleneglycol) dichlorides and oligo(ethyleneglycol) ditosylates. Compounds with ring sizes ranging from 18-crown-6 to 42-crown-14 were prepared. In addition, various altered benzimidizoles were used to produce DBTA crown ethers with modified substituents and ether bridges, as well as benzimidazolidine crown ethers. The synthetic approach presented here proved to be a convenient route to a new family of crown ethers with overall yields of up to 48% based on the benzimidazole. Yields for the ring-closing step were generally high, ranging from 51% to 94%, without the need for high-dilution conditions. Reaction of the DBTA crown ethers with alkyl and benzyl halides was found to be a facile way to obtain the corresponding tetra(N-organyl) compounds. Picrate extraction studies were carried out to determine phase-transfer catalytic capabilities. Extraction efficiencies for alkali-metal ions were lower than those for dibenzo-18-crown-6. Efficiencies were higher for other metal ions, with some selectivity for Pb(2+). Tetra(N-methyl) DBTA-18-crown-6 generally exhibited higher extraction efficiencies than its N-H analogue, but the selectivity was lower.     

含萘并呋喃基团冠醚的合成及离子选择性研究

以2-羟基-1-萘甲醛和2-羟甲基冠醚为原料,合成3种新的含萘并呋喃基团冠醚(3a-3c),并经1 H NMR,13C NMR,MS及元素分析确证.碱金属和碱土金属离子的加入对体系的最大吸收波长影响不大.Li+使3b摩尔吸光度变大,Ca2+和Ba2+引起3a-3c最大发射波长λem发生相对较大红移,同时使其荧光强度降低.     

Synthesis of lysine derivatives containing aza-crown ethers and a chromophore unit

The synthesis of a lysine-like chromo-ionophore and its derivatives, useful in peptide chemistry, is described. The influence of the peptide framework on the anthraquinone properties is examined with spectroscopic and electrochemical methods.     

Synthesis and optical characterization of novel azacrown ethers containing an acridinone or an N-methylacridinone unit as potential fluorescent chemosensors

Four new achiral and four new chiral monoazacrown ethers containing an acridinone or an N-methylacridinone fluorescent signalling unit were prepared by reacting chloromethyl-substituted acridinone derivatives with achiral monoazacrown ethers with different cavity sizes and enantiopure monoaza-18-crown-6 ethers having two methyl and two isobutyl groups on their chiral centres, respectively. The operation of these chemosensors is based on the photoinduced electron transfer (PET) process, thus they show fluorescence enhancement in the presence of cationic guests. Their fluorescent behaviour as well as their complexation properties towards selected metal ions and the enantiomers of α-(1-naphthyl)ethylammonium perchlorate and potassium mandelate were examined.     

Redox responsive crown ethers containing a direct link between the ferrocene redox-active centre and benzo crown ether. Crystal structure of a ferrocene benzo-15-crown-5 sodium complex

The binding of Na⁺, K⁺ and Mg²⁺ to benzo-15-crown-5 and aza-15-crown-5 directly-linked ferrocenes results in shifts of the ferrocene oxidation wave to more positive potentials. The magnitude of these anodic shifts is related to the charge/radius ratio of the cationic guest. The results of an X-ray diffraction study of the structure of a ferrocene benzo-15-crown-5 sodium complex are also reported.     

Extraction of biogenic amines using sorbent materials containing immobilized crown ethers

Three sorbent materials (A18C6-MS, DA18C6-MS and AB18C6-MS) based on the crown ether ligands, 1-aza-18-crown-6, 1,4,10,13-tetraoxa-7,16-diazacyclo octadecane and 4′-aminobenzo-18-crown-6, respectively, were prepared by the chemical immobilization of the ligand onto mesoporous silica support. The sorbents were characterized by FT-IR, scanning electron microscopy-energy dispersive X-ray microanalysis, elemental analysis and nitrogen adsorption-desorption test. The applicability of the sorbents for the extraction of biogenic amines by the batch sorption method was extensively studied and evaluated as a function of pH, biogenic amines concentration, contact time and reusability. Under the optimized conditions, all the sorbents exhibited highest selectivity toward spermidine (SPD) compared to other biogenic amines (tryptamine, putrescine, histamine and tyramine). Among the sorbents, AB18C6-MS offer the highest capacity and best selectivity towards SPD in the presence of other biogenic amines. The AB18C6-MS sorbent can be repeatedly used three times as there was no significant degradation in the extraction of the biogenic amines (%E > 85). The optimized procedure was successfully applied for the separation of SPD in food samples prior to the reversed-phase high performance liquid chromatography separation.     

Synthesis and crystal structures of some cobalt halide derivatives containing alkyl or silanolato groups

The alkylcobalt halide (2) and the lithium silanolatocobaltates Li(THF)₂(μ-Br)₂Co(μ-OSiMe₃)₂Co(μ-Br)₂Li(THF)₂ (4) and [LiBr{Li(THF)}₂{CoBr(OSiMe₃)₃}]₂ (5) form centrosymmetrical halogen-bridged dimers in the crystalline state. Compound 4 shows bromide bridges between lithium and cobalt, and silanolato bridges between the cobalt atoms. Below 200 K there are significant antiferromagnetic interactions between the cobalt centres. Compound 5 crystallises in a novel structure in which two cubane-like fragments containing silanolato bridges are linked together through a Li₂Br₂ ring.