Reactions of 2,5-di(2-thienyl)pyrroles

We have studied the possible modification of 2,5-di(thienyl)pyrroles with the aim of preparing compounds which can serve as precursors of polymers and monomers showing electrical conductivity and specific photochemical properties. Dedicated to Boris Aleksandrovich Trofimov on his 70^th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1356–1365, September, 2008.     

An approach to the Paal-Knorr pyrroles synthesis catalyzed by Sc(OTf)3 under solvent-free conditions

A facile synthesis of N-substituted pyrroles by the Paal-Knorr condensation has been accomplished using a simple procedure. Among different metal triflates screened, 1 mol % Sc(OTf)₃ efficiently promoted the reaction to give excellent yield (89-98%) under mild reaction conditions. Additionally, Sc(OTf)₃ could be recovered easily after the reactions and reused without evident loss in activity.     

Facile,efficient and eco-friendly synthesis of 5-sulfenyl tetrazole derivatives of indoles and pyrroles

A concise, two-step eco-friendly approach towards the synthesis of 5-sulfenyl tetrazole derivatives of indoles and pyrroles, is reported. The synthesis comprises the oxone-mediated thiocyanation of the starting heterocycles towards intermediate 3-thiocyanato indoles and 2-thiocyanato pyrroles, and their subsequent treatment with sodium azide in 2-propanol/water under zinc bromide promotion.     

TiO2-coated graphene oxide-molybdate complex as a new separable nanocatalyst for the synthesis of pyrrole derivatives by Paal-Knorr reaction

The preparation of chemical and pharmaceutical compounds through organic reactions has always been associated with the production of environmental waste. Growth population and concerns about ecological pollution increase the interest in using heterogeneous solid catalysts with capabilities such as increasing reaction efficiency and reducing the production of by-products, as well as the ability to separate and reuse. To develop and benefit such catalysts as much as possible, in this study, using graphene oxide (GO) as a support, we succeeded in preparing a heterogeneous catalyst with a high contact surface, excellent performance, and recyclability. Graphene oxide nanosheets were synthesized according to Hummer’s method. hexamolybdate anions ([n-Bu₄N]₂[Mo₆O₁₉]) were placed on this support as a catalytically active site using linkers. The structure of this catalyst was confirmed by XRD, FT-IR, EDS, SEM, TEM, TGA, Raman, and nitrogen adsorption–desorption analyses, and it was used to produce pyrroles by the Paal-Knorr method. The performance of the synthesized nanocatalyst was satisfactory for all the derivatives studied. Recovery and reuse of GO@TiO₂@(CH₂)₃N = Mo[Mo₅O₁₈] after catalytic reactions were examined. This catalyst could be quickly recovered by simple filtration and recycled ten times without significant loss of its catalytic activity.     

Synthesis of 5-aryl-2-oxopyrrole derivatives as synthons for highly substituted pyrroles

A small library of 2-oxo-5-(hetero)arylpyrroles was prepared starting from 2,3-dioxo-5-(hetero)arylpyrrolidines. The large synthetic possibilities of these 2-oxopyrroles were investigated. The 2-oxopyrroles offer a large number of possible derivatizations including reactions with electrophiles. The chloroformylation of 2-oxo-5-(hetero)arylpyrroles provides pyrrole carbaldehydes. Some pyrrole carbaldehydes were used to synthesize polycyclic compounds like pyrrolo[3,4-d]pyridazinones, a thienopyrrole, a pyrrolobenz[1,4]oxazepine, a pyrrolobenzo[1,4]thiazepine, and a pyrrolobenzo[1,4]diazepine. Hereby we showed through a short exploration that the oxopyrroles and analogues are interesting and versatile synthetic building blocks.     

Facile Synthesis of Unsymmetrical N-Aryl-2, 2-di(1H-indol-3-yl) Acetamide Derivatives

A facile and highly efficient method has been developed for the synthesis of unsymmetrical N-aryl-2,2-di(1H-indol-3-yl)acetamide derivatives by regioselective Friedel-Crafts alkylation of the N-aryl-2-hydroxy-2-(1H-indol-3-yl) acetamide derivatives with various indoles catalyzed by 2 mol/L H₂SO₄ at room temperature in a short reaction time, the yield was up to 94%.     

Direct cyclization of ortho-(1H-pyrrol-1-yl)aryl and heteroaryl carboxylic acids into fused pyrrolizinones

A series of fused heterocyclic compounds based on a pyrrolizinone structure have been prepared from ortho-(1H-pyrrol-1-yl)aryl and heteroaryl carboxylic acids by intramolecular Friedel-Crafts acylation promoted by bis(trichloromethyl) carbonate, in generally good yield without using Lewis acid catalysts.     

First synthesis and structural report on selenophen-2-yl containing pnictogens: Biological activities of tris(selenophen-2-yl)stibine

A new tertiary stibine and bismuthine containing C-heterocyclic selenophene ring have been synthesized. Tris(2-selenophenyl)stibine (1) and tris(2-selenophenyl) bismuthine (2) and characterized by IR, MS, ¹H, ¹³C, COSY, HETCOR NMR spectroscopy. Crystal structures of stibine and bismuthine have been determined. In an attempted synthesis of tris(2-selenophenyl) phosphine, an oxidative product tris(2-selenophenyl) phosphine oxide (3) was isolated under the experimental conditions used, whose X-ray crystal structure was also determined. To best of our knowledge C-heterocyclic selenophene-2-yl pnictogens are first of their kind, as not many examples are known even with other p-block metal/metalloids.The biological activity of compound (1) was determined. The compound (1) shows a significant selectivity (>85%) for carcinogenic cell K and U growth inhibition. The toxicity of tris(selenophen-2-yl) stibine (1) on larvae of Artemia Salina was studied and the LC₅₀ value was 589.6 μM.     

Transformation of 3-(Furan-2-yl)-1,3-di(het)arylpropan-1-ones to Prop-2-en-1-ones via Oxidative Furan Dearomatization/2-Ene-1,4,7-triones Cyclization

The approach to 3-(furan-2-yl)-1,3-di(het)arylprop-2-en-1-ones based on the oxidative dearomatization of 3-(furan-2-yl)-1,3-di(het)arylpropan-1-ones followed by an unusual cyclization of the formed di(het)aryl-substituted 2-ene-1,4,7-triones has been developed. The cyclization step is related to the Paal–Knorr synthesis, but the furan ring formation is accompanied in this case by a formal shift of the double bond through the formation of a fully conjugated 4,7-hydroxy-2,4,6-trien-1-one system or its surrogate.     

An efficient and selective synthesis of 2,5-substituted pyrroles by gold-catalysed ring expansion of alkynyl aziridines

A range of substituted alkynyl aziridines undergo a ring expansion to afford 2,5-substituted pyrroles under gold catalysis. While effective conditions can be generated from other gold sources, a combination of Ph₃PAuCl and AgOTs generate a catalyst system that provides extremely clean cycloisomerisation reactions requiring minimal work-up and purification.     

Facile synthesis of trisubstituted imidazoles from 1,2-di(furan-2-yl)-2-oxoethyl carboxylates and their chemiluminescence

A facile synthesis of trisubstituted imidazoles containing furan rings was reported. Imidazoles were produced from 1,2-di(furan-2-yl)-2-oxoethyl carboxylates over solid alumina as solid support impregnated with ammonium acetate under solvent-free microwave-assisted conditions. The method possessed many remarkable advantages, such as the short reaction time (5–10 min), affording moderate to excellent yields and saving resources, conveniently operating process, which provided an attractive and environmentally-friendly approach for the synthesis of the important heterocyclic compounds. Moreover, the chemiluminescence property of some compounds synthesized has been investigated.     

Spectral-luminescence properties of some 2,5-dihydroxy-1,4-di(azol-2-yl)benzenes

The influence of the type of azole fragments and substituents on the spectral-luminescence properties of a series of 2,5-dihydroxy-1,4-di(azol-2-yl)benzenes, possessing an anomalously high Stokes shift, was investigated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 242–245, February, 1993.     

Silica sulfuric acid (SSA) as a solid acid heterogeneous catalyst for one-pot synthesis of substituted pyrroles under solvent-free conditions at room temperature

A variety of N-substituted pyrroles have been synthesized by reacting γ-diketones with amines, diamines or triamine in the presence of silica sulfuric acid (SSA) at room temperature under solvent-free conditions. The experiment protocol features simple operations, and the products are isolated in high to excellent yields (70-98%).     

Facile synthesis of pyrroles via Rh(II)-catalyzed transannulation of 1-tosyl-1,2,3-triazoles with silyl or alkyl enol ethers

A novel Rh(II)-catalyzed transannulation of 1-tosyl-1,2,3-triazoles with silyl or alkyl enol ethers has been developed, which enables the facile synthesis of substituted pyrroles in a regiocontrollable manner. Moreover, the methodology could be extended to access 3-pyrrolin-2-one derivatives with silyl ketene acetals used as the reaction partner.     

Lanthanide bis(trifluoromethanesulfonyl)amides, synthesis, characterization and catalytic activity

The synthesis of lanthanum, neodymium and ytterbium bis(trifluoromethanesulfonyl)amides, named triflimidates, from acetates, carbonates and oxides is investigated. When the synthesis is performed in water, all the salts contain one molecule of water and the lanthanum and neodymium salts synthesized from the acetates also contain one molecule of acetic acid. After removal of the water and acetic acid in refluxing ethanol, the salts are obtained anhydrous but associated for lanthanum and neodymium, whereas the ytterbium salt is monomeric and volatile. When the synthesis is performed directly in ethanol, the neodymium salt contains two molecules of coordinated ethanol.In non-hazardous solvents, these triflimidates are better catalysts than the analogous triflates toward either Friedel-Crafts acylations, or Fries transpositions or Baeyer-Villiger oxidations. Unexpectedly, the cerium(IV) triflimidate catalyzes the oxidation of aromatic ketones to give the corresponding acids.     

A facile synthesis of indole-furan conjugates via integration of convergent and linear domino reactions

The convergent and linear domino reactions have been first integrated, for the first time, to provide an efficient synthesis of indole-furan conjugates from indoles, methyl ketones, and 1,3-dicarbonyl compounds.     

N-substituted 2,5-di(2-thienyl)pyrroles: application,production, properties,and electrochemical polymerization (review)

In this review methods for the synthesis of substituted 2,5-di(2-thienyl)pyrroles are described, and various aspects of their application are discussed. The main emphasis is on the electrochemical behavior of the compounds, the possibility of their electrochemical polymerization, and their use as monomers for the production of conducting polymers – components for molecular electronics.     

11,11,12,12-四氰基-2-对甲基苯基-9,10-蒽醌二甲烷的合成及其光谱性能

以邻苯二甲酸酐和对溴甲苯为原料,经Friedel-Crafts酰基化、浓硫酸催化、Suzuki偶联及Knoevenagel缩合合成了一种新型的四氰基-9,10-蒽醌二甲烷衍生物——11,11,12,12-四氰基-2-对甲基苯基-9,10-蒽醌二甲烷(5),其结构经1H NMR,ESI-MS和元素分析表征。UV-Vis和荧光光谱研究表明,5在249 nm,332 nm和426nm有较强吸收;在375 nm激发波长激发下,5的最大发射波长在595 nm。     

Microwave assisted highly efficient one-pot multi-component synthesis of novel 2-(tetrasubstituted-1H-pyrrol-3-yl)-4H-chroman-4-ones catalyzed by heterogeneous reusable silica gel supported polyphosphoric acid (PPA/SiO2)

A solvent-free, eco-friendly and facile approach for the synthesis of highly functionalized tetrasubstituted pyrroles has been reported through one-pot four-component reaction of aldehyde, amine, nitroalkane and 1,3-diketone using silica gel supported polyphosphoric acid (PPA–SiO₂) under microwave condition. The reaction occured through the in situ formation of β-keto enamine and nitrostyrene analog following Michael addition and finally intramolecular annulation affording the products in good yields. The key features of the present method include clean reaction, mild conditions, low catalyst loading, straightforward, high to excellent yields, short reaction time, avoiding use of harmful metal catalyst and organic solvent, environmentally friendly compared to the existing methods, recovery and reusability of catalyst and easy workup procedure.