A new variant of Knorr''''s pyrrole synthesis

The reaction between ethyl 3-bromopyruvate and p-substituted anilines was found to involve the unexpected participation of acetone (solvent) forming N-aryl-5-methyl-pyrrole-3-carboxylates.The influence of p-substituents of aniline and the feasibility with other ketones were studied.N-aryl-indole-3-carboxylate (17) was synthesized successfully with this method.The unique character of p-methoxy-aniline in this reaction was discussed.     

Anion binding by pyrrole–pyridine-based macrocyclic polyamides

The synthesis, characterisation and anion-binding properties of new pyrrole–pyridine-based macrocyclic polyamides 7a and 7b are presented. Chloride anion templation in the macrocyclisation reaction has been shown to control [1 + 1] acylation. The anion-binding properties of the receptors have been determined by UV–vis titrations in a DMSO solution and compared with systems with a similar design. The new receptors have been found to display a 10-fold selectivity for hydrogensulphate, dihydrogenphosphate and acetate anions over other anions studied.     

α-Nitro chalcones: Structure and reaction with pyrrole

According to the ¹H NMR, IR, and electronic absorption spectra and X-ray diffraction data, 2-aryl-1-benzoyl-1-nitroethenes have E configuration with predominant s-cis conformation, where the nitro group lies in the plane of the double carbon-carbon bond, while the carbonyl group deviates from that plane. Reactions of 2-aryl-1-benzoyl-1-nitroethenes with pyrrole and N-methylpyrrole gave the corresponding alkylation products at the C² atom in the heteroring.     

Synthesis of cyclodextrin–pyrrole conjugates possessing tuneable carbon linkers

Cyclodextrins are naturally occurring cyclic oligosaccharides consisting of glucose units. The main feature of cyclodextrins is the ability to accommodate various lipophilic compounds in their interior, which determines them to be popular helpers to the mankind. However, there is still a demand for new derivatives for advanced applications. Herein, we report the synthesis of β-cyclodextrin–pyrrole conjugates. Their preparation is based on an amide bond formation or copper(I)-catalysed azide-alkyne cycloaddition between β-cyclodextrin and pyrrole derivatives. The main advantage of the synthetic approach lies in the possibility to attach the substituent in β-position, because polypyrroles possessing a substituent in this position are generally more conductive than the N-substituted ones. Moreover, the presented synthetic route is general and allows tuning the properties (various types of connections and lengths) of a linker. The presented cyclodextrin–pyrrole derivatives thus open the door for new applications in the field of sensors or tissue engineering.     

Synthesis of bisquinoline–pyrrole oligoamide as G-quadruplex binding ligand

A one-pot procedure using ammonium formate under palladium catalysis for the reductive dechlorination and reduction of nitro group of 4-chloro-8-nitro–quinoline derivatives has be successfully carried out. This has lead to the synthesis of bisquinoline–pyrrole oligoamide 1, which show significant G-quadruplex selectivity in preference to duplex DNA. The cooperativity between the bisquinoline and pyrrole oligoamide moieties for good binding affinity to G-quadruplex was proven by synthesizing 2 and 3 lacking a quinoline ring and pyrrole amide, respectively, and both show much reduce affinity to G-quadruplex. Altogether, the results demostrate that the appropriate combination of two chromophores to form the hybride can attenuate binding affinity and selectivity towards G-quadruplex, an important criteria for the rational drug design.     

Catalytic synthesis of higher pyrrole and pyrrolidine homologs from α-furylalkylamines

Summary The vapor-phase hydrogenation of 1-furyl-3-aminoheptane and 1-furyl-3-aminononane over Pt-asbestos leads to the hydrogenolysis of the furan ring with the subsequent formation of a new nitrogen heterocycle by ring-closure. At 220°, 2-n-propyl-5-n-butyl- and 2-n-propyl-5-n-hexylpyrrolidines are formed with yields of 90% of theoretical, and at 300° the corresponding pyrroles with yields of 85%.     

电子化物Li_3@calix[4]pyrrole和Li_3O@calix[4]pyrrole的结构及非线性光学性质的理论研究

对超碱金属电子化物Li3@calix[4]pyrrole和Li3O@calix[4]pyrrole的几何结构、相对稳定性和非线性光学性质进行了理论研究.2个体系分别含有4个和2个稳定异构体.通过与Li@calix[4]pyrrole比较发现,以超碱金属Li3和Li3O为电子供体可以给体系带来更大的非线性光学响应.当Li3和Li3O分子平面与calix[4]pyrrole配体的4个N原子构成的平面平行作用时,超碱金属的电离程度更高,体系具有更大的一阶超极化率值.     

Nucleation of β-hairpin structure in a pyrrole amino acid containing peptide

Synthesis and conformational studies of two short peptides containing pyrrole amino acids (1, Paa), Boc-Paa-Paa-d-Pro-Gly-Xaa-Paa-Paa-OMe (2: Xaa=Ala; 3: Xaa=Val), were carried out in which it was established that replacement of Ala in 2 with a Val residue helps peptide 3 to adopt a well-defined β-hairpin conformation in a nonpolar solvent, like CDCl₃.     

Friedel–Crafts acylation of pyrrole over ultrasonic-assisted phosphoric acid-modified Hβ zeolite

Friedel?CCrafts acylation of pyrrole with acetic anhydride was studied over different zeolites and an ultrasonic-assisted phosphoric acid-modified H?? (P-H??-US) zeolite was found to have the best catalytic performance among all the zeolites examined. The conversion of acetic anhydride reached 98.8% and the selectivity to acetylpyrroles was 97.0% under the optimized conditions. The high activity of the P-H??-US zeolite is attributed to the increase of weak acid sites, caused by the synergistic effect between the phosphoric acid modification and ultrasound. Moreover, the carbonaceous deposits, mainly due to the adsorption of reactants and products, on the surface acid sites and the blockage of the pores is believed to be the reason for the deactivation of the reused P-H??-US zeolite, confirmed from the Brunauer?CEmmett?CTeller (BET) method, scanning electron microscopy, and X-ray photoelectron spectroscopy. Furthermore, the catalyst activity can be recovered effectively by a subsequent calcination.     

Chemical reactivity of the imidazole: a semblance of pyridine and pyrrole?

It has been suggested that pyridine and pyrrole could be patterns for imidazole reactivity studies due to the amine (-NH-) and aza (-N═) nitrogen atoms. The analyses of the local and global electronic indexes prove and quantify that imidazole has an intermediate analogy between pyrrole and pyridine.     

Aluminum chloride–catalyzed C-alkylation of pyrrole and indole with chalcone and bis-chalcone derivatives

The AlCl₃-catalyzed alkylation of pyrrole (2) with chalcone (1a–i) at a ratio of 8:1 in the presence of 10 mol% AlCl₃ gave the solely 2-alkyl pyrroles (3a–i) at room temperature for 12 in good yields. The same reaction was performed with pyrrole (2) and chalcone at a ratio of 1:3 in CH₃CN at rt for 3 h to achieve 2,5-dialkyl pyrroles (4a–f). In addition, the reaction of the pyrrole (2) and indole (7) on 1,4-phenylene bis-chalcones (5a–g) at the ratio of 8:1 at rt for 24 h gave the double-addition products 6a–g and 8a–g in good yields, respectively. The structure of the products was confirmed by ¹H and ¹³C NMR spectroscopy and elemental analysis.     

Electrochemical fabrication of novel fluorescent polymeric film: Poly(pyrrole–pyrene)

We describe herein the electrochemical characterization and polymerization of 4-pyren-1-yl-butyric acid 11-pyrrol-1-yl-decyl ester (pyrrole–pyrene) in CH₃CN. The electrochemical oxidation of the pyrrole group at 0.77 V vs Ag/Ag + 10 mM in CH₃CN led to the first example of a fluorescent polypyrrole film. The mechanism of deposition on platinum electrode was studied by voltammetry and chronoamperometry. The optical properties of the polymeric films electrogenerated on ITO electrodes were examined by UV–visible spectroscopy and fluorescence microscopy indicating an increase in fluorescence properties by increased polymer thickness. The electrochemical oxidation of pyrenyl group linked to the polypyrrole backbone was carried out at 1.2 V. This additional polymerization was demonstrated by UV–visible spectroscopy and induced the loss of the fluorescence properties of the resulting polymeric film.     

Synthesis and Crystal Structure of 3,5-Diphenyl- 1,2- di（4- chlorophenyl）pyrrole

1 INTRODUCTION The pyrrole ring constitutes a basic heteroaro- matic structure. It is a vital building block for the construction of porphyrins and alkloids[1]. Several substituted pyrroles have potential applications as fungicides and bactericides and as active compo- nents of nonsteroidal anti-inflammatory drugs inhi- biting human cyclooxygenase[2, 3]. Besides the clas- sical Knorr’s method, there are a number of poten- tially useful methods for the synthesis of pyrrole he- terocyclic …     

Electrogeneration and characterization of a poly(pyrrole–nickel (II) chlorin) electrode

We describe herein, the electrochemical properties of an hydroporphyrin of Ni(II) substituted by two pyrrole groups in organic media (THF and CH₂Cl₂). In the anodic region it has been shown that the electrochemical behaviour of this complex investigated by cyclic voltammetry and coulometry coupled with UV–visible spectroscopy is strongly dependent on the nature of the solvent.Furthermore, the electrochemical oxidation of the pyrrrole groups has led to the first example of an electrogenerated polypyrrole–metallochlorin film. The resulting modified electrodes exhibit the same electrochemical properties as the monomer free in solution. Preliminary experiments have also demonstrated the possibility to study electrochemically this polymeric film in CH₃CN contrary to the Ni(II) chlorin, which is insoluble in this medium.     

Synthesis of chiral pyrrolidine and pyrrole derivatives through the chemoselective Dieckmann reaction of α,β-aminodiesters

α,β-Aminodiesters were allowed to react with t-BuOK in THF at −78°C. The chemoselectivity of the Dieckmann cyclization was controlled by the nature of the substituents R₃ and R₄, allowing the preparation of pyrrolidine or pyrrole derivatives.     

Synthesis, crystal structures, and supramolecular assemblies of pyrrole-based anion receptors bearing modified pyrrole β-substituents

Dipyrrolyldiketone BF(2) complexes acting as acyclic anion receptors form supramolecular assemblies with structures and properties that are dependent on the pyrrole β-substituents. In particular, although β-alkyl substituents interfered with the formation of stable gel states, the introduction of fluorine moieties induced a stable supramolecular gel when compared to that of β-unsubstituted receptor.     

Colorimetric sensing of fluoride ion by new expanded calix[4]pyrrole through anion-π interaction

Three new expanded calix[4]pyrroles were synthesized, where the two dialkylldipyrromethane units are linked via C-C double bonds. One of them, calix[2]bispyrrolylethene, colorimetrically senses fluoride ion only, owing to anion-π interaction in polar aprotic solvents.     

Gallium trichloride-catalyzed conjugate addition of indole and pyrrole to α,β-unsaturated ketones in aqueous media

Michael addition of indole and pyrrole to a variety ofα,β-unsaturated ketones was efficiently promoted by a catalytic amount of GaCl_3 in aqueous media to afford the corresponding products in good to excellent yields.     

Synthesis of trifluoromethyl derivatives of pyrrole. Reaction of α,β-unsaturated trifluoromethyl ketones with sodium cyanide

An efficient preparative procedure was developed for the synthesis of 5-hydroxy-5-trifluoromethyl-2-pyrrolidones by the reaction of ,-unsaturated trifluoromethyl ketones with sodium cyanide. Dehydration of these reaction products under mild conditions afforded previously unknown 5-trifluoromethyl-3-pyrrolin-2-ones.     

The third-order NLO properties of D-π-A molecules with changing a primary amino group into pyrrole

The nonlinear refractive index, as well as the two-photon absorption (TPA), has been investigated by the femtosecond Z-scan method for push–pull molecules, in which a primary donor group is weakened by conversion into a pyrrole or related heterocycle. The results at the fast response time show that, contrary to what had been expected from a previous work, there is a little decrease in the nonlinear refractive index change by introduction of the weaker donor groups. Although the measured TPA spectra showed that the observed nonlinear refractive index change was regarded to be off-resonant; difference in the frequency dispersion among the molecules considerably contributes to the decrease, in addition to difference in the intrinsic static nonlinearity. This shows that there is some future in the development of these non-resonant materials.