Alkylation Of Pyrroles Research Articles

Copper Triflate Catalyzed Regioselective Alkylation of Pyrrole: Conversion of 2-Alkylated Pyrroles to Novel Pyrrolizine Derivatives by Self-Cyclization

Metal triflate catalyzed addition reaction of pyrrole to methyl 2-oxo-4-phenylbut-3-enoate and substituted derivatives generated the related novel alkylated pyrroles regioselectively at C(2) of pyrrole. Among the studied metal triflates, Cu(OTf) 2 was found to be more effective in the addition reaction. The synthesized methyl 2-oxo-4-phenyl-4-(1H-pyrrole-2-yl)butanoate esters underwent self-cyclization by heating and yielded the corresponding methyl 3-hydroxy-l-phenyl-2,3-dihydro-1H-pyrrolizine-3-carboxylate and substituted derivatives. This reaction procedure allowed easy access to pyrrolizine structure in mild reaction conditions.

Synthesis and characterization of novel bead-shaped insoluble polymer-supported tri-site phase transfer catalyst and its efficiency in N-alkylation of pyrrole

Abstract A new bead-shaped insoluble polymer-supported multi-site (tri-site) phase transfer catalyst (PS-MPTC) viz., polymer-supported 4-(2,2,2-tris[triethylammoniummethylene chloride]-1-hydroxy ethyl) phenylether (PSTTEACHPE) has been synthesized by following a simplified procedure. Initially, polystyrene-based cross-linked beads was prepared by allowing the reaction using 2% divinylbenzene (as a cross linking monomer), 25% vinylbenzyl chloride (as a functional monomer) and styrene (as supporting monomer) to proceed through a suspension copolymerization method. The obtained terpolymer beads containing pendant benzyl chloride groups were condensed with 4-(2,2,2-tris[triethylammonium methylene chloride]-1-hydroxy ethyl) phenol, followed by quaternization using triethylamine, resulting in the formation of polymer-supported 4-(2,2,2-tris[triethylammoniummethylene chloride]-1-hydroxy ethyl) phenyl ether (PSTTEACHPE). Then the presence of tri-active site in PSTTEACHPE was examined by FT-IR, 1 H NMR, 13 C NMR, [chloride ion] and SEM analyses. The comparative results of [chloride ion] and the peak intensity of C–N stretching (quaternary onium group) in FT-IR were found to increased three fold in PSTTEACHPE on comparing with their similar types of polymer-supported bead-shaped single-site PTC (PS-BSPTC); thus we confirmed the presence of three active sites. The surface morphology study through SEM shows that the PSTTEACHPE is heterogeneous in nature with tiny nodules; whereas the single-site PS-BSPTC shows smooth homogeneous nature; this is an another piece of evidence for the availability of more numbers of active sites in PSTTEACHPE. Further, the catalytic efficiency of this new PSTTEACHPE was ascertained by N -alkylation of pyrrole with benzylchloride using 30% (w/v) aqueous sodium hydroxide at 60 °C. The pseudo-first order rate constants were calculated by following the disappearance of pyrrole through gas chromatography. The observed rate constants were found to be three-fold higher for PSTTEACHPE than with PS-BSPTC, which again confirmed the presence of three active-sites. Investigations were also made on kinetic variables such as stirring speed, [substrate], [catalyst], [NaOH] and temperature; it is observed that each variable is influenced the rate of reaction. From the Arrhenius plot, the activation energy and thermodynamic parameters were evaluated as 12.44, −7.99, 10.99 and 13.25 kcal mol −1 for E a , Δ S # , Δ H # and Δ G # respectively. Based on the observed kinetic and thermodynamic results, an interfacial mechanism was proposed for the N -alkylation of pyrrole.

Synthesis, polymerization and wool coating studies of 3- iso-butylpyrrole and 3- iso-pentylpyrrole

In a four-step method starting from pyrrole, the synthesis of 3- iso-butylpyrrole and 3- iso-pentylpyrrole, was achieved in 45 and 44% yields, respectively. Polymerization studies of these branched alkyl pyrroles are described and the results compared with those obtained for the unbranched structural isomers n-butyl and n-pentylpyrrole. A series of conductive textiles were produced by the chemical polymerization of the iso-alkylpyrroles using both solution and vapour polymerization techniques. Fabrics coated with poly- iso-alkylpyrrole formed using the solution polymerization method had a lower surface resistance than those formed using the vapour polymerization method. These conductivity results were in direct contrast to those previously obtained for 3- n-alkylpyrroles on fabrics. A remarkable crystal-like growth on the surface of the textile fabric was observed when solution polymerization of 3- iso-pentylpyrrole was employed—reinforcing the notion that subtle changes in monomer structure can drastically affect bulk polymer properties.

Asymmetric synthesis of 1-benzyl-2-(( S)-2′,2′-dimethyl-1′,3′-dioxolan-4′-yl)-1 H-pyrrole using chiral imines

A new synthesis of chiral alkyl pyrroles and pyrrolines has been achieved in an easy straightforward way, using the addition of organometallics to chiral imines.

Et3B‐Mediated Radical Alkylation of Pyrroles and Indoles.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Pd‐Catalyzed Allylic Alkylation of Pyrroles with Allyl Alcohols Promoted by Triethylborane.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Pd-catalyzed Allylic Alkylation of Pyr- roles with Allyl Alcohols Promoted by Triethylborane

Triethylborane promotes the Pd-catalyzed allylic alkylation of pyrroles with a variety of allylic alcohols to provide either C2 allylation products (a,a-, γ,γ-dimethylallyl alcohol and geraniol) or C2,C5 diallylation products (allyl alcohol, α-, β-, γ-methyl-, and α-, γ-phenylallyl alcohols) in good to excellent yields under mild conditions.

Mono‐ and Dialkylations of Pyrrole at C2 and C5 Positions by Nucleophilic Substitution Reaction in Ionic Liquid.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Mono- and Dialkylations of Pyrrole at C2 and C5 Positions by Nucleophilic Substitution Reaction in Ionic Liquid

[reaction: see text] A novel ionic liquid methodology for pyrrole C-alkylation is described. The pyrrole alkylation is achieved with various simple alkyl halides and mesylates selectively at C2 and C5 positions in good yields with minimal byproducts under relatively mild conditions in various ionic liquids. 2-(3-Phenylpropyl)pyrrole (2a) was synthesized from pyrrole and 1-bromo-3-phenylpropane in a mixture solvent system, [bmim][SbF6] and CH3CN, in 81% yield at 115 degrees C for 44 h with 5% yield of dialkylated compound 3a.

Montmorillonite Clay Catalyzed Alkylation of Pyrroles and Indoles with Cyclic Hemi‐Acetals.

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Montmorillonite clay catalyzed alkylation of pyrroles and indoles with cyclic hemi-acetals

Cyclic hemiacetals such as 2-deoxy- d-ribose and 2-deoxy- d-glucose react smoothly with pyrroles and indoles on the surface of montmorillonite KSF clay under extremely mild reaction conditions to afford optically active di-pyrrolyl and bis-indolyl alkanols in good yields with high selectivity.

Zinc‐Mediated Barbier Reactions of Pyrrole and Indoles: A New Method for the Alkylation of Pyrrole and Indoles.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Zinc-mediated Barbier reactions of pyrrole and indoles: a new method for the alkylation of pyrrole and indoles

Pyrrole and indoles react smoothly with alkyl halides such as allyl bromide, prenyl bromide, crotyl bromide and propargyl bromide in the presence of zinc metal in THF to afford the corresponding 3- and 2-alkyl pyrrole and 3-alkyl indole derivatives in good yields with high regioselectivity.

ChemInform Abstract: Stereoselectivity in the Double Reductive Alkylation of Pyrroles: Synthesis of cis‐3,4‐Disubstituted Pyrrolidines.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Stereoselectivity in the double reductive alkylation of pyrroles: synthesis of cis-3,4-disubstituted pyrrolidines

The preparation and Birch reduction of a 1,3,4-tri-substituted pyrrole is described: the heterocycle is loaded with electron-withdrawing groups and undergoes a double reductive alkylation reaction to yield cis-3,4-disubstituted pyrrolidines.

ChemInform Abstract: Selective Alkylation of Pyrrole by Phase Transfer Catalysis in the Absence of Solvent.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Selective alkylation of pyrrole by phase transfer catalysis in the absence of solvent

AbstractSelective N‐alkylation of pyrrole is performed, in good yield and by a very simple method, using Phase Transfer Catalysis in the absence of solvent.

Pyrolysis GC/MS studies on plasma‐polymerized pyrrole

AbstractPyrolysis gas chromatography/mass spectrometry and infrared spectrometry have been carried out for plasma‐polymerized pyrrole (PPPy). The major thermal decomposition products have been identified as nitriles with less than four carbons and alkyl pyrroles. Evolution of only monosubstituted alkyl pyrroles, such as 2‐methylpyrrole and 2‐ethylpyrrole, suggests that PPPy consists of monosubstituted pyrrole rings. This is also supported by the result that the IR spectrum of PPPy differs from that of the electrochemically polymerized pyrrole, which consists of disubstituted pyrrole rings. Evolution of linear nitriles shows evidence that a PPPy molecule has the main chain containing nitrogen atoms. The mechanism of polymerization of pyrrole in the discharge is considered to be similar to that of aromatic hydrocarbons, which mechanism involves a process of production of acetylene. © 1993 John Wiley & Sons, Inc.

Langmuir-Blodgett films of polyheterocycles: A study with synchrotron radiation techniques

Novel electroactive Langmuir-Blodgett (LB) films have been assembled from 3-alkyl pyrroles and poly(3-alkyl thiophenes). The films were transfered onto platinum-coated glass slides and their molecular orientation was studied using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The 3-alkyl pyrroles are sufficiently surface active to form LB films owing to the considerable dipole moment of the pyrrole ring. The polythiophenes, however, are not sufficiently surface active by themselves, but form high quality LB films as mixtures with stearic acid. 3-Alkyl pyrroles derivatized with ferrocene moieties have also been incorporated into LB films as mixtures with alkyl pyrrole to produce highly ordered structures. The NEXAFS spectra also reveal evidence of strong charge transfer interaction between the heterocyclic head groups and the platinum substrate.

Alkylation of Pyrrole with Tert-Butanol in the Presence, of Cation Exchanger Amberlyst 15

Abstract Alkylation of pyrrole with tert-butanol in the presence of strongly acidic cation exchanger (Amberlyst 15) represents a one-step high-yield route to 2- and 3-tert-butylpyrroles.