Anion binding studies of fluorinated expanded calixpyrroles

The anion binding properties of fluorinated calix[n]pyrroles (n = 4-6) in aprotic solvents (acetonitrile and DMSO) and modified reaction conditions allowing for the synthesis and isolation of the hitherto missing dodecafluorocalix[6]pyrrole from the condensation of 3,4-difluoro-1H-pyrrole and acetone are described. In acetonitrile solution containing 2% water, the association constants for the 1:1 binding interaction between octafluorocalix[4]pyrrole and chloride anion obtained with isothermal titration calorimetry (ITC) and (1)H NMR titration methods were found to match reasonably well. As compared to its nonfluorinated congener, octafluorocalix[4]pyrrole was found to display enhanced binding affinities for several representative anions in pure acetonitrile as judged from ITC analyses. Similar analyses of the fluorinated calix[n]pyrroles revealed an increase in the relative affinity for bromide over chloride with increasing macrocycle size, as manifest in a decrease in the binding ratio K(a(Cl))/K(a(Br)). Anion binding studies in the solid state, involving single-crystal X-ray diffraction analyses of the chloride and acetate anion complexes of octafluorocalix[4]pyrrole and decafluorocalix[5]pyrrole, respectively, confirmed the expected hydrogen bond interactions between the pyrrolic NH protons and the bound anions.     

Silver-catalyzed intramolecular aminofluorination of activated allenes

A nice combination: The intramolecular oxidative aminofluorination of allenes using silver catalysis and FN(SO(2) Ph)(2) as the fluorinating reagent has been developed. This reaction represents an efficient method for the synthesis of various 4-fluoro-2,5-dihydropyrrole compounds. Further transformation provided the corresponding fluorinated pyrrole derivatives in good yields.     

Gas-phase kinetic measurements of the ligation of Ni+, Cu+, Ni(pyrrole)1,2+ and Cu(pyrrole)1,2+ with CO2, D2O, NH3 and NO

The rate and equilibrium kinetics of the reactions of the biologically important metal species M(+), M(+)(pyrrole) and M(+)(pyrrole)(2) (M = Ni, Cu) have been investigated with the biological gases CO(2), D(2)O, NH(3) and NO in the gas phase at 295 +/- 2 K in helium buffer-gas at a pressure of 0.35 +/- 0.01 Torr. The measurements were taken with an Inductively Coupled Plasma/Selected-Ion Flow Tube (ICP/SIFT) tandem mass spectrometer. Only ligation was observed for the reactions of bare Ni(+) and Cu(+) with CO(2), D(2)O and NH(3) with rates consistent with the known strengths of the resulting ligand-metal bonds. Both metal cations appeared to be oxidized and produce N(2)O in interesting reactions that are second order in NO. One pyrrole ligand was observed to increase the rate of ligation by as much as a factor of 100 and to switch off the oxidation with NO. Equilibrium was achieved for the ligation of CO(2), D(2)O and NO to both Ni(+)(pyrrole) and Cu(+)(pyrrole), and so it was possible to determine absolute values for the standard free energies of ligation. No ligand substitution was observed with M(+)(pyrrole). M(+)(pyrrole)(2) was observed to be generally unreactive towards the small molecules investigated: a notable exception is ammonia. Very fast ligand substitution reactions were observed for reactions of M(+)(pyrrole)(2) with NH(2).     

A highly enantiopure biconcave porphyrin with effective D4-structure

A first representative of an effectively D4-symmetric biconcave porphyrin (1) was prepared from a tetramerizing condensation of a C2-symmetric pyrrole (2). The chiral pyrrole 2 was synthesized in a six-step reaction sequence starting from the C2h-symmetric 2,6-di-tert-butylanthracene. The relevant stereochemistry was introduced in a highly diastereo-discriminating Diels-Alder reaction with fumaric acid di(-)menthyl ester, catalyzed by aluminum chloride. X-ray analyses of two of the dimenthyl esters prepared unambiguously secured their tentatively assigned absolute configuration and that of the pyrrole 2 (as the S,S isomer). The enantiomeric purity of the pyrrole 2 was determined as 99% ee, using the Co11 complex of the porphyrin 1 as a chiral shift reagent. The pyrrole 2 lent itself to a stereochemically nearly uniform preparation of the chiral, biconcave porphyrin 1. Applying Horeau's principle, 1 was calculated to be present in an enantiomeric excess of about 10(9):1. The validity of the statistical considerations relevant for this estimate were verified by examination of the results from preparative tetramerization experiments in which the enantiomeric purity of the pyrrole 2 was deliberately lowered.     

Enzymatic formation of pyrrole-containing novel cyclic polyprenoids by bacterial squalene:hopene cyclase

A convergent synthesis provided two pyrrole-containing squalene analogues, in which a C₂₀ isoprene unit is connected to pyrrole, 2-(geranylgeranyl)pyrrole and 2-(farnesyldimethylallyl)pyrrole. When incubated with recombinant squalene:hopene cyclase from Alicyclobacillus acidocaldarius, 2-(farnesyldimethylallyl)pyrrole was enzymatically converted to a 10:1 mixture of a tricyclic and a bicyclic unnatural novel polyprenoids, whereas 2-(geranylgeranyl)pyrrole was not a substrate for the enzyme.     

一种新型α-甲醚基吡咯的合成

以乙酰乙酸苄酯(4)为原料, 经Knorr缩合制备了2,4-二甲基-3-丙酸甲酯基-5-羧酸苄酯基-1-氢吡咯 (2) 和2,4-二甲基-3-羧酸甲酯基-5-羧酸苄酯基-1-氢吡咯(3)。乙醚介质中,溴水氧化条件下,吡咯 (2) 发生自身缩合生成二吡咯甲烷 (7),吡咯 (3)无反应发生。在Pb(OAC)₄氧化条件下,当其浓度为吡咯 (3)浓度的2倍时,在80 ℃,吡咯 (3) 完全转华。所得产物经HCl甲醇溶液回流,以82%的产率制备了新型2-甲氧基甲基-3-羧酸甲酯基-4-甲基-5-羧酸苄酯基-1氢吡咯 (1)。吡咯(1)、(2)、(3)及二吡咯(7)的结构用核磁、元素分析、质谱和红外等测试技术进行了表征。吡咯(1)的构建对进一步研究吡咯构效关系具有一定参考价值。     

Beta-octafluorocorroles

The one-pot corrole synthesis first reported by the Gross and Paolesse groups appears to have evolved into a remarkably general and predictable self-assembly based synthetic reaction. Gross's solvent-free procedure (refs 8 and 9) has proven particularly effective in our hands and, in fact, more general than originally claimed. In earlier work (ref 17), we showed that the reaction works for a variety of aromatic aldehyde starting materials and was not limited to relatively electron-deficient aldehydes, as reported by Gross and co-workers. Here, we show that the pyrrole component is also variable in that 3,4-difluoropyrrole undergoes oxidative condensation with four different p-X-substituted benzaldehydes to yield the corresponding beta-octafluoro-meso-tris(para-X-phenyl)corroles (X = CF3, H, CH3, and OCH3). Further, we have prepared the Cu and FeCl derivatives of the beta-octafluorocorrole ligands. The XPS nitrogen 1s ionization potentials of these fluorinated ligands are some 0.7 eV higher than those of the corresponding beta-unfluorinated ligands. The oxidation half-wave potentials of the Cu and FeCl complexes of the fluorinated corroles are also positively shifted by 300-400 mV relative to their beta-unsubstituted analogues, demonstrating the strongly electron-deficient character of the fluorinated ligands. 1H NMR spectroscopy suggests that like their beta-unfluorinated counterparts, the new beta-octafluorinated triarylcorroles act as substantially noninnocent ligands, i.e., exhibit corrole pi-cation radical character, in the FeCl complexes. Quantitatively, however, NMR spectroscopy and DFT calculations indicate that the beta-octafluorinated corroles are somewhat less noninnocent (i.e., carry less radical character) than their beta-unfluorinated counterparts in the FeCl complexes. Temperature-dependent 19F NMR spectroscopy suggests that the Cu octafluorocorroles have a thermally accessible paramagnetic excited state, which we assign as a Cu(II) corrole pi-cation radical. We have previously reported that the electronic absorption spectra, particularly the Soret absorption maxima, of high-valent transition metal triarylcorroles are very sensitive to the nature of the substituents in the meso positions. In contrast, the Soret absorption maxima of free-base triarylcorroles are not particularly sensitive to the nature of the meso substituents. This scenario also holds for the fluorinated corroles described here. Thus, although the four free-base fluorinated triarylcorroles exhibit practically identical Soret absorption maxima, the Soret bands of the Cu derivatives of the same corroles red-shift by approximately 35 nm on going from the p-CF3 to the p-OCH3 derivative.     

Preparation and applications of a variety of fluoroalkyl end-capped oligomer/hydroxyapatite composites

A variety of fluoroalkyl end-capped oligomers were applied to the preparation of fluorinated oligomer/hydroxyapatite (HAp) composites (particle size: 38-356 nm), which exhibit a good dispersibility in water and traditional organic solvents. These fluoroalkyl end-capped oligomer/HAp composites were easily prepared by the reactions of disodium hydrogen phosphate and calcium chloride in the presence of self-assembled molecular aggregates formed by fluoroalkyl end-capped oligomers in aqueous solutions. In these fluorinated HAp composites thus obtained, fluoroalkyl end-capped acrylic acid oligomers and 2-methacryloyloxyethanesulfonic acid oligomer/HAp nanocomposites afforded transparent colorless solutions toward water; however, fluoroalkyl end-capped N,N-dimethylacrylamide oligomer and acryloylmorpholine oligomer were found to afford transparent colorless solutions with trace amounts of white-colored HAp precipitants under similar conditions. HAp could be encapsulated more effectively into fluorinated 2-methacryloyloxyethanesulfonic acid oligomeric aggregate cores to afford colloidal stable fluorinated oligomer/HAp composites, compared to that of fluorinated acrylic acid oligomers. These fluorinated oligomer/HAp composites were applied to the surface modification of glass and PVA to exhibit a good oleophobicity imparted by fluorine. HAp formation was newly observed on the modified polyethylene terephthalate film surface treated with fluorinated 2-methacryloyloxyethanesulfonic acid oligomers and acrylic acid oligomer/HAp composites by soaking these films into the simulated body fluid.     

Tri- and pentacalix[4]pyrroles: synthesis, characterization and their use in the extraction of halide salts

Calixpyrrole-based oligomeric compounds were synthesized by "click chemistry" from the corresponding alkyne- and azide-functionalized calix[4]pyrroles. Calix[4]pyrrole 3, possessing an alkyne functional group, was prepared through a mixed condensation of pyrrole with acetone and but-3-ynyl 4-oxopentanoate. Another alkyne-group-containing calix[4]pyrrole 5 was obtained by treatment of 4'-hydroxyphenyl-functionalized calixpyrrole 4 with propargyl bromide. Tetrakis(azidopentyl)-functionalized calix[4]pyrrole 7 was synthesized by reacting NaN(3) with tetrabromopentyltetraethylcalix[4]pyrrole 6, which was prepared through a condensation reaction of pyrrole and 7-bromohept-2-one. Oligomeric calixpyrrole compounds were found to be capable of extracting tetrabutylammonium chloride and fluoride salts from aqueous media. Extraction abilities of the oligomeric compounds were monitored by NMR and UV/Vis spectroscopy and thermogravimetric analysis.     

Alkylthio unit as an alpha-pyrrole protecting group for use in dipyrromethane synthesis

The synthesis of porphyrin precursors requires the successive introduction of substituents at the pyrrole alpha- and alpha'-positions (2- and 5-, respectively). An alpha-pyrrole substituent that serves as a temporary masking agent and is not deactivating would greatly facilitate such syntheses, particularly for beta-(3,4)-unsubstituted pyrroles, but has heretofore not been available. A series of alpha-RS groups (R = Me, Et, n-decyl, Ph) have been investigated in this regard, including the determination of the kinetics of substitution at the pyrrolic 3-, 4-, and 5-positions and the application to dipyrromethane formation. The RS group was readily introduced into the pyrrole alpha-position by the reaction of 2-thiocyanatopyrrole (prepared from pyrrole, ammonium thiocyanate, and iodine) and the corresponding Grignard reagent RMgBr. Each 2-alkylthio group activated the pyrrole ring toward deuteration at the 3- or 5- (vs 4-) position. The dipyrromethane synthesis was carried out using a 2:1 ratio of 2-(RS)pyrrole/benzaldehyde with a catalytic amount of InCl3 at room temperature in the absence of any solvent. The alpha-RS group was removed by hydrodesulfurization using Raney nickel or nickel complexes. This stoichiometric synthesis using the alpha-RS-protected pyrrole is in contrast to the traditional synthesis that employs an aldehyde and 25-100 mol equiv of pyrrole. Six meso-substituted dipyrromethanes were prepared by the reaction of 2-(n-decylthio)pyrrole/aldehyde/InCl3 (2.2:1:0.2 ratio) followed by hydrodesulfurization. Other reactions of the 1,9-bis(RS)dipyrromethane include oxidation to give (i) the 1,9-bis(RS)dipyrrin or (ii) the 1,9-bis(RSO2)dipyrromethane, which underwent subsequent complexation with dibutyltin dichloride. In summary, under mild reaction conditions, the 2-alkylthio group is readily introduced to the pyrrole nucleus, directs electrophilic substitution to the 5-position, and is readily removed as required for elaboration of porphyrinic precursors.     

Preparation of fluoroalkyl end-capped oligomers/magnetite nanocomposites possessing a good dispersibility and stability

Fluoroalkyl end-capped vinylphosphonic acid cooligomers-encapsulated magnetite nanocomposites were prepared by the magnetization of aqueous ferric and ferrous ions in the presence of the corresponding fluorinated cooligomers and magnetic nanoparticles under alkaline conditions. These fluorinated cooligomers magnetic composites are nanometer size-controlled very fine particles and have a good dispersibility and stability in water and traditional organic solvents. These fluorinated nanocomposites were also applied to the surface modification of poly(methyl methacrylate) to exhibit a good oleophobicity imparted by fluorine on their surface. Fluoroalkyl end-capped 2-methacryloyloxyethanesulfonic acid oligomer-encapsulated magnetite nanocomposites and fluoroalkyl end-capped 2-acrylamide-2-methylpropanesulfonic acid oligomer-encapsulated magnetite nanocomposites were prepared in good isolated yields by the magnetization of iron chlorides in the presence of the corresponding oligomers and magnetic nanoparticles under similar conditions. Colloidal stability of these fluorinated nanocomposites thus obtained in water was demonstrated to become extremely higher than that of fluorinated vinylphosphonic acid cooligomers/magnetic nanocomposites.     

Siloxane-functionalized calix[4]pyrrole: synthesis, characterization and modification of silica-based solid supports

A siloxane-functionalized calix[4]pyrrole derivative was synthesized starting from the corresponding alcohol-functionalized calix[4]pyrrole. Structural elucidation was carried out by using NMR spectroscopy, mass spectrometry and X-ray diffraction analysis. The use of this siloxane-functionalized calix[4]pyrrole for modification of various silica solid supports (silica gel 60, fume silica, and SiO₂ nanopowder) was studied. Characterization of the modified silica solid supports was achieved by FTIR, TGA, and elemental analysis. It was also shown that the production of silica nanoparticles is possible via a sol-gel reaction of siloxane-functionalized calix[4]pyrrole and tetraethoxysilane (TEOS). Calix[4]pyrrole modified silica solid supports were found to sense chloride anions of Azure A dye.     

Polycondensed heterocycles. I. Synthesis of 11-oxo-5H, 11H-pyrrolo[2,1-c][1,4]benzothiazepine,Derivative of a novel ring system

The synthesis of the title compound 4 by cyclization of 1-(2-ethoxycarbonylthiobenzyl)pyrrole 9 , prepared by treating with ethyl chloroformate the 1-(2-mercaptobenzyl)pyrrole 7 previously obtained by debenzylation of 1-(2-benzylthiobenzyl)pyrrrole 6 , failed. On the other hand 4 was successfully synthesized by intramolecular cyclization of 1-(2-mercaptobenzyl)pyrrole-2-carboxylic acid 15 by DMAP -catalyzed DCC method. The pyrrole 6 and 1-(2-benzylthiobenzyl)pyrrole-2-carboxaldehyde 11 were useful as starting materials to obtain 1-(2-benzylthiobenzyl)pyrrole-2-carbonitrile 13 , which was hydrolyzed to corresponding amide 16 . Debenzylation of 16 afforded 1-(2-mercaptobenzyl)pyrrole-2-carboxyamide 17 , whose hydrolysis led to required acid 15 .     

Henry reaction of fluorinated nitro compounds

The Henry (nitroaldol) reaction of fluorinated nitro compounds with various aromatic aldehydes and a fluorinated aliphatic aldehyde to give β-fluoro-β-nitroalcohols which bearing a fluorinated quaternary carbon center was reported. The relative configuration of the major diastereoisomer of 2-fluoro-2-nitro-1-(4-nitrophenyl)-3-phenylpropanol (5bf) was determined by X-ray single crystal analysis.     

Effect of substituents in directing the formation of benzochlorins and isobacteriochlorins in porphyrin and chlorin systems

[formula: see text] A first synthesis of free-base fluorinated benzochlorins by acid-catalyzed cyclization of 20-(2-trisiloxy-trifluoromethylvinyl)octaethylporphyrin++ + is achieved. Under similar reaction conditions, the purpurin-18-N-hexylimide analogues produced the corresponding fluorinated and nonfluorinated ethylidene-substituted isobacteriochlorins and fluorinated chlorin, respectively. The structure of the porphyrin based fluorinated benzochlorin was also confirmed by X-ray analysis.     

Nucleophilic fluoroalkylation of epoxides with fluorinated sulfones

The unprecedented nucleophilic fluoroalkylation of simple epoxides with fluorinated sulfones was achieved to give the beta-fluoroalkyl alcohols in one step. The negative "fluorine effect" in the nucleophilic fluoroalkylation of epoxides with fluorinated carbanions was probed by the reactivity comparison between carbanions PhSO2CF2- (3) and PhSO2CCl2- (4) and between carbanions PhSO2CHF- (7) and PhSO2CHCl- (13). The mediation of this fluorine effect by introducing another electron-withdrawing benzenesulfonyl group was found to be an effective way to significantly increase the nucleophilicity of the fluorinated carbanions, with the reactivity order [(PhSO2)2CF-] (16) > PhSO2CFH- (7) > PhSO2CF2- (3).     

Comparison of benzene, nitrobenzene, and dinitrobenzene 2-arylsulfenylpyrroles

The effectiveness of the 2,4-dinitrobenzenesulfenyl and 4-nitrobenzenesulfenyl groups as masking and directing groups at the 2-position of pyrrole has been investigated and compared to that of 2-phenylthiopyrrole. The presence of the nitro group(s) enhances stability of the corresponding pyrrole toward acid and does not significantly decrease the ability of the pyrrolic unit to undergo electrophilic aromatic substitution reactions in the form of formylation, nitration, and condensation with aldehydes. The synthetic utility of 2-(2,4-dinitrobenzenesulfenyl)pyrrole was demonstrated through the synthesis of meso-substituted dipyrromethanes. The sulfoxides 2-(2,4-dinitrobenzenesulfinyl)pyrrole and 2-(4-nitrobenzenesulfinyl)pyrrole underwent neither formylation nor nitration, and the increasing presence of nitro groups within the moiety at the 2-position resulted in decreased stability under acidic conditions.     

Skeletal Diversity in Catalytic Synthesis of (1,3-Oxazacycloalk-3-ylmethyl)-Substituted Pyrroles

Russian Journal of General Chemistry - A series of bi- and trinuclear pyrrole derivatives was prepared by the 5 mol % ZrOCl2 ·8H2O-catalyzed CH-sp2-aminomethylation reaction of pyrrole with...     

氟含量对含氟丙烯酸酯共混乳胶膜梯度结构和表面性能的影响

首先将制备出的平均粒径较小的含氟丙烯酸酯均聚物乳液与平均粒径较大的纯丙烯酸酯共聚物乳液按不同的比例( 1/9,2/8,3/7,4/6,5/5)共混,接着将各共混乳液在室温下(20℃)玻璃基材上干燥后,于110℃/210℃下热处理一段时间.运用接触角法,XPS、AFM、SEM-EDX等详细研究了共混乳胶膜中含氟组分含量对...     

Preparation and characterization of a novel fluorinated acrylate resin

The novel fluorinated acrylate resin was successfully prepared by solution polymerization of 2-(perfluoro-(1,1-bis-isopropyl)-2-propenyl)oxyethyl methacrylate (POMA) with butyl acrylate (BA), methyl methacrylate (MMA) and methacrylic acid (MAA) initiated by AIBN in the co-solvents of ethyl acetate, butyl alcohol and toluene. POMA was synthesized from the intermediate perfluoro nonene and 2-hydroxyethyl methacrylate as the staring reactants. Films of the novel fluorinated acrylate resin were prepared by coating the resin directly on the clean glass sheet and allowed to dry at room temperature. The characteristics of the film such as hydrophobicity, glass transition temperature and thermal stability were characterized with the contact angle, differential scanning calorimetry and thermo-gravimetric analysis respectively. The structure of the novel fluorinated acrylate resin was investigated by Fourier transform infrared (FTIR) spectrometry. The influences of the fluorine content on the performance of the acrylate resin were studied. Results show that the hydrophobicity, chemical resistance, glass transition temperature and thermal stability of the acrylate resin are improved when the fluorinated monomer is introduced to copolymerize with other monomers. However, the hydrophobicity of the fluorinated acrylate resin is improved slightly via annealing.