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The (1)H, (13)C and (15)N NMR studies have shown that the E and Z isomers of pyrrole-2-carbaldehyde oxime adopt preferable conformation with the syn orientation of the oxime group with respect to the pyrrole ring. The syn conformation of E and Z isomers of pyrrole-2-carbaldehyde oxime is stabilized by the N-H...N and N-H...O intramolecular hydrogen bonds, respectively. The N-H...N hydrogen bond in the E isomer causes the high-frequency shift of the bridge proton signal by about 1 ppm and increase the (1)J(N, H) coupling by approximately 3 Hz. The bridge proton shows further deshielding and higher increase of the (1)J(N, H) coupling constant due to the strengthening of the N-H...O hydrogen bond in the Z isomer. The MP2 calculations indicate that the syn conformation of E and Z isomers is by approximately 3.5 kcal/mol energetically less favorable than the anti conformation. The calculations of (1)H shielding and (1)J(N, H) coupling in the syn and anti conformations allow the contribution to these constants from the N-H...N and N-H...O hydrogen bondings to be estimated. The NBO analysis suggests that the N-H...N hydrogen bond in the E isomer is a pure electrostatic interaction while the charge transfer from the oxygen lone pair to the antibonding orbital of the N-H bond through the N-H...O hydrogen bond occurs in the Z isomer., (2010 John Wiley & Sons, Ltd.)

According to the (1)H, (13)C and (15)N NMR spectroscopic data and DFT calculations, bifurcated N--H...N and N--H...O intramolecular hydrogen bond is shown to be present in 2-trifluoroacetyl-5-(2'-pyridyl)-pyrrole. This bifurcated hydrogen bond causes an increase in the absolute size of the (1)J(N,H) coupling constant by about 6 Hz, and the deshielding of the bridge proton by 2 ppm. DFT calculations show that the influence of the N--H...N and N--H...O intramolecular hydrogen bonds on the (1)J(N,H) coupling and proton shielding is almost additive, although the components of the bifurcated hydrogen bond slightly weaken each other. In 2-trifluoroacetyl-5-(2'-pyridyl)-pyrrole, the coupling constants involving the fluorine and the N--H covalent bond nuclei depend dramatically on the spatial position of the pyridine ring. The pyridine ring rotation operates as a quantum switch controlling the spin information transfer between the (19)F and (15)N nuclei, as well as the proton., (Copyright (c) 2007 John Wiley & Sons, Ltd.)

2-(2,2-Dicyano-1-ethylsulfanylethenyl)pyrroles readily react (ethanol, reflux) with aniline at position 1 of the ethenyl moiety in the presence of triethylamine to eliminate ethanethiol affording 1-anilino-3-iminopyrrolizine-2-carbonitriles or 2-(1-anilino-2,2-dicyanoethenyl)pyrroles in good yields. [ABSTRACT FROM AUTHOR]

2- and 2,3-Substituted pyrroles are readily synthesized in a one-pot procedure from ketones, hydroxylamine hydrochloride, and 1,2-dichloroethane in the KOH/DMSO system (120 °C, 2–4 h), the yields of pyrroles ranging 11–85%. Aliphatic, cycloaliphatic, aromatic, and heteroaromatic ketones tolerate the reaction conditions. [ABSTRACT FROM AUTHOR]

The reaction between 1-methylimidazole, cyano(phenyl) acetylene, and 1-vinylpyrrole-2-carbaldehydes (MeCN, 20-25 °C) stereoselectively gives 1-vinylpyrrole-imidazole ensembles with a (Z,Z)-bis(2-cyano-1-phenylvinyl)oxy function in up to 45% yield. Unlike recently reported three-component reaction between imidazoles, electron-deficient acetylenes, and aldehydes affording 1:1:1 adducts, in this case two molecules of acetylene are involved to deliver 1:2:1 adducts thus representing a novel functionalizaton of the pyrrole-imidazole alkaloid scaffold. The initial zwitterion generated from imidazole and cyano(phenyl)acetylene is thought to be transformed into a carbene, which reacts with pyrrole-2-carbaldehyde. Two subsequent rearrangements of the 1:1:1 adduct furnish the intermediate pyrrole-imidazole ensemble, which in its enol form adds to second molecule of cyano(phenyl)acetylene to yield the final products, functionalized pyrrole-imidazole alkaloids. [ABSTRACT FROM AUTHOR]

Abstract: 1-Vinylpyrrole-2-carbaldehydes and 1-vinyl-4,5-dihydrobenzo[g]indole-2-carbaldehyde were synthesized in 56–91% yields from their 1-vinyl derivatives by a modified Vilsmeier–Haack reaction. A low temperature (−78°C) is required to avoid removal of the N-vinyl group, whereas at elevated temperature (reflux in 1,2-dichloroethane) the latter process leads to direct conversion of 1-vinylpyrroles to pyrrole-2-carbaldehydes. [Copyright &y& Elsevier]

New 2-(1-alkylthio-2-dicyanoethenyl)pyrroles or 2-(1-alkylthio-2-cyano-2-carbamoylethenyl)pyrroles of Z -configuration have been synthesized in 58-69% yields by the reaction of pyrrole-2-carbodithioates with CH-acids (malononitrile, cyanoacetamide) in KOH-DMSO. Condensation of ethyl 4,5,6,7-tetrahydroindole-2-carbodithioate with ethyl benzyl malonate affords a mixture (1 : 2) of 1-ethylthio-2-benzyloxycarbonyl-4,5,6,7-tetrahydrocyclohexa[ c ]pyrrolizine-3-one and 1-ethylthio-2-ethoxycarbonyl-4,5,6,7-tetrahydrocyclohexa[ c ]pyrrolizine-3-one. [ABSTRACT FROM AUTHOR]

The reaction of pyrrole-2-carbodithioates with methylenoactive nitriles and 2-benzoyl-1-bromoacetylene in the KOH-DMSO system leads to functionally substituted pyrrolothiazoles in 59-85% yield. [ABSTRACT FROM AUTHOR]

The reaction provides an access to alkyl, aryl, and hetaryl 2-substituted and 2,3-disubstituted pyrroles. [ABSTRACT FROM AUTHOR]

Abstract: A new highly synthetically potent series of bifunctional pyrroles, 1-vinylpyrrole-2-carbonitriles, were synthesized from readily available 1-vinylpyrrole-2-carbaldehyde oximes by two methods: (1) reaction with acetylene (KOH/DMSO, 70°C, 10min, yields 58–67%) and (2) reaction with acetic anhydride (90–100°C, 5h, yields 83–93%). Starting from 2-phenyl-1-vinylpyrrole, the one-pot synthesis of the corresponding 1-vinyl-2-carbonitrile was accomplished directly by successive treatment with a DMF/(COCl)2 complex, NH2OH·HCl/NaOAc, and acetic anhydride (yield 58%). [Copyright &y& Elsevier]

Abstract: 5-Amino-3-(pyrrol-2-yl)isoxazoles were selectively prepared by the reaction of 2-(2,2-dicyano-1-ethylthioethenyl)pyrroles with hydroxylamine in methanol. Under analogous conditions, 2-(2-carbamoyl-2-cyano-1-ethylthioethenyl) pyrroles with hydroxylamine gave 5-aminoisoxazoles and their structural isomers, 3-aminoisoxazoles (3–5% yield). The latter were selectively prepared by reacting 2-(2-carbamoyl-2-cyano-1-ethylthioethenyl)pyrroles with hydroxylamine in the presence of aqueous NaOH and from the products of intramolecular cyclization of 2-(2-carbamoyl-2-cyano-1-ethylthioethenyl)pyrroles, 1-ethylthio-3-iminopyrrolizines and hydroxylamine. [Copyright &y& Elsevier]

Rare nonaromatic 3 H -pyrroles have been synthesized from ketoximes having only one C–H bond adjacent to the oxime function and acetylene under pressure (10–13 atm) at 70 °C in two-phase superbase media of KOH/DMSO/ n -hexane type, the yields ranging 8–36%. The effect of substituents, superbase nature and reaction conditions on yields of the target 3 H -pyrroles has been analyzed. Hydroxypyrroline/3 H -pyrroles interconversion as well as relative stability of model 3 H -pyrroles have been assessed quantum chemically (MP2/6-31++G**//B3LYP/6-31G**). [ABSTRACT FROM AUTHOR]

2-(Furan-2-yl)- and 2-(thiophen-2-yl)pyrroles are readily ethynylated with acylbromoacetylenes in the solid Al 2 O 3 medium (no solvent, room temperature, 1 h) to afford 5-(furan-2-yl)- and 5-(thiophen-2-yl)-2-acylethynylpyrroles in 39–74% yields. In the case of 2-(furan-2-yl)pyrroles, an alternative ethynylation of the furan ring takes place, the ratio of the furan and pyrrole ring ethynylation products being 1:5–7. No ethynylation of the thiophene ring as well as ethynylation of both heterocycles in a one molecule has been detected. Thus the reactivity of the heterocycles towards the ethynylation system (acylbromoacetylenes/Al 2 O 3 ) falls in the order: pyrrole>furan>thiophene. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis of fluorophores of the family of meso-CF3-substituted BODIPY 1a–e obtained from the corresponding dipyrromethanes 2a–e involves the oxidation of the latter followed by the complexation of the dipyrromethenes formed to boradiazaindacenes. The transformation of dipyrromethanes 2a–e into BODIPY 1a–e is accompanied by the characteristic high-frequency shifts of the 13C NMR signals of pyrrole ring carbons in the same position relative to the nitrogen atoms and substituents. Acceptor character of the BF2 group relative to the pyrrole moiety is also manifested in the significant increase of the 13C chemical shifts of carbon atoms of the aryl or hetaryl substituents in the positions 3 and 5 of the BODIPY complexes in comparison with those of the initial dipyrromethanes. In the thienyl derivatives of BODIPY, a prominent high-frequency shift of the 1H resonance of the proton in position 3 of the thiophene ring, induced by the spatial proximity of the fluorine atoms of the BF2 group, is revealed. Such a proximity is the cause of the effective transmission of the long-range 19F–13C spin–spin coupling via the intermediate Che calculations in the framework of density functional theory (DFT) of the thienyl derivative of meso-CF3-BODIPY show the preference in energy for the anti conformation of the thienyl ring with respect to the boradiazaindacene core, so that the hydrogen atom in position 3 of the thienyl ring and one of the fluorine atoms of the BF2 group turn out to be spatially close to each other by a distance less than the sum of their van der Waals radii. Topological analysis of the F⋯H interaction parameters within the Quantum Theory of Atoms In Molecules (QTAIMs) and the orbital interactions in considering of the Natural Bond Orbitals (NBOs) formalism reveal that this interaction is much weaker than the conventional intramolecular hydrogen bond, although it is quite sufficient to explain the observed spectral effects. [Copyright &y& Elsevier]

Abstract: A novel family of nitrogen stilbene analogs, 1-styrylpyrroles, has been synthesized in good to excellent yields by a straightforward facile transition metal-free addition of pyrroles to arylacetylenes in the KOH/DMSO system (90–120°C, 5–13h). Thermodynamically controlled E/Z-isomer ratio of 1-styrylpyrroles depends on structure of both pyrroles and acetylenes ranging from ca. 100% E-stereoselectivity (for the pair unsubstituted pyrrole—phenylacetylene) to 90, 96% Z-stereoselectivity (for the pairs: 2-phenylpyrrole—phenylacetylene and 2-(2-thienyl)pyrrole—phenylacetylene, respectively). [Copyright &y& Elsevier]

Abstract: I2-doped and pyrrole ring-iodinated semi-conducting oligomers of N-vinyl-3-alkyl-2-phenylpyrroles have been synthesized by free-radical polymerization of the above monomers (AIBN, 2–5wt%, 60–80°C) and further exposure of the oligomers obtained to I2 vapor. The parent oligomers exhibit paramagnetic and fluorescent properties and stable up to 300–370°C. [ABSTRACT FROM AUTHOR]

Abstract: Cationic polymerization of N-vinyl-2-phenylpyrrole (catalysts: Me3SiCl, CF3COOH, BF3·OEt2, HCl, WCl6, FeCl3, complex LiBF4–dimethoxyethane, catalysts concentration 1–2wt%, 20–70°C, 24–48h) affords oligomers (molecular weight 1400–1700) of a unexpected structure with alternating 2-phenylpyrrole and ethylydene units, the yields reaching 63%. The oligomers structure has been supported by isolation and identification of the corresponding dimer, N-vinyl-2-phenyl-5-[N-(2-phenyl-1H-pyrrol-1-yl)ethyl]-1H-pyrrole. Radical polymerization of the same monomer (AIBN, 1.5–4wt%, 60–80°C, 40–60h or UV irradiation or both) gives oligomers (molecular weight 2100–3000) of normal structure having polyethene backbone with pendant 2-phenylpyrrole groups in up to 40% yields. The oligomers of both types are semiconductors (1.3×10−6–3.6×10−6 S/cm) after doping with I2, paramagnetic (4.2×1017–8.7×1017 g−1) and fluorescent in a near UV region (λ 355–363nm, acetonitrile). [Copyright &y& Elsevier]

Abstract: 2-Arylazo-1-vinylpyrroles 1–6 react with CF3CO2H (benzene, reflux, 5h) in a peculiar way: instead of expected electrophilic addition of CF3CO2H to the N-vinyl group, the latter is transferred to the azo group followed by Neavage to afford substituted 2-methylquinolines 10–12 in up to 56% yields. The reaction was shown (1H, 13C, and 15N NMR) to start with the protonation of the azo group with further inter- and intramolecular involving of two protonated N-vinyl groups to finally build up the quinoline cycle over the aryl moiety. [Copyright &y& Elsevier]

Abstract: 2-Aryl-1-vinylpyrroles in acetone, THF and benzene react with tetracyanoethene chemo- and regiospecifically across the vinyl group to give 3-(2-arylpyrrol-1-yl)-1,1,2,2-cyclobutanetetracarbonitriles in 88–94% yield. The latter, upon recrystallization from EtOH, eliminates HCN and entirely rearranges to afford stereospecifically trans-(3E)-4-(2-arylpyrrol-1-yl)-1,3-butadiene-1,1,2-tricarbonitriles. In DMSO, along with the above [2+2]-cycloaddition, tricyanovinylation of the pyrrole ring occurs to form the corresponding 3- and 5-tricyanovinylpyrroles, the product ratio being dependent on the substituents in the pyrrole ring and the reaction conditions. [Copyright &y& Elsevier]

The reaction of oximes of aromatic ketones with phenylacetylene in the presence of superbase systems (MOH-DMSO, where M = Li, Na, K) has been extensively studied for the first time. The effects of alkaline metal cation, the ketoximes structure and the reaction conditions (temperature, duration) on the products composition have been evaluated. Acetophenone oxime reacts with phenylacetylene (MOH-DMSO, where M = Li, Na, K, 140 °C, 6 h) to afford 2,5-diphenyl-1H-pyrrole in 14-18% isolated yield. The reaction of benzylphenylketoxime with phenylacetylene (LiOH-DMSO, 120 °C, 12 h) delivers 2,3,4-, 2,3,5-triphenyl-1H-pyrroles (in 17% total yield) and 2,3,4-triphenyl-1-[(Z)-2-phenylethenyl]-1H-pyrrole (7% yield). [ABSTRACT FROM AUTHOR]

Abstract: The solvent-free interaction of 2-phenylpyrrole with bromobenzoylacetylene (room temperature) upon their grinding with solid metal oxides (MgO, CaO, ZnO, BaO, Al2O3, TiO2, ZrO2) and salts (CaCO3, ZrSiO4) leads to either the cross-coupling product or the adduct of pyrrole addition to the riple bond of acetylene. The ethynylation is accompanied by the formation of intermediate and side products: E-2-(1-bromo-2-benzoylethenyl)-5-phenylpyrrole and 1,1-di(5-phenylpyrrol-2-yl)-2-benzoylethene. The activity of the metal oxides in the ethynylation reaction falls in the order (in the brackets, the content of 2-benzoylethynyl-5-phenylpyrrole in the reaction mixture is given): ZnO (81%), BaO (73%), Al2O3 (71%), MgO (69%), CaO (50%). The oxides, SiO2, TiO2, ZrO2, and the salts, CaCO3 and ZrSiO4, are inactive in the ethynylation reaction affording only the intermediate adduct, with ZrO2 the isolated yield of the bromoethenylpyrrole reaching 60%. ESR monitoring shows the reaction to start from one electron transfer from pyrrole to acetylene mediated by the oxide surface. The adduct is readily converted on Al2O3 to 2-(benzoylethynyl)-5-phenylpyrrole crystallized mostly as cis-rotamer (X-ray data). [Copyright &y& Elsevier]

Abstract: Functionalized pyrrolic enols, 2-(2,2-dicyano-1-hydroxyethenyl)-1-methylpyrroles, synthesized from 2-ethenylpyrroles by a nucleophilic SEt-OH exchange, upon heating (75–142°C) are readily rearranged to their 3-isomers in near to quantitative yield. The inter or intramolecular auto-protonation of a pyrrole ring by the acidic enol hydroxyl to form a mesomeric pyrrolium cation or zwitterion is suggested to be a key step in the rearrangement. [Copyright &y& Elsevier]

Abstract: 2-(2-Cyano-1-ethylthioethenyl)pyrroles easy exchange their ethylthio group for hydroxyl (NaOH, H2O–methanol, 40–45°C, 1h) to give 2-(2-cyano-1-hydroxyethenyl)pyrroles, a new family of stable enols, in 50–94% yields. The vinylic nucleophilic substitution proceeds at the double bond of both the starting pyrroles and their cyclic isomers, 3-iminopyrrolizines. X-ray structure analysis and NMR spectra show the enols to be stabilized by exceptionally strong intramolecular H-bonding. [Copyright &y& Elsevier]

Discusses the reactivity of C-vinylpyrroles and their application as building blocks in the synthesis of more complex pyrrole compounds. Addition reactions to the vinyl group; Photodimerization of 1-aryl-2-pyrrolylethenes; Hydrosilylation; Substitution of hydrogen or functional groups at the double bond.

The protonation of the E/Z mixture of pyrrole-2-carboxaldehyde oxime (CF3COOH, Et2O or CDCl3, room temperature) gives Z-configured pyrrole-2-carboxaldehyde oxime cations exclusively. The NMR (1H, 13C and 15N) analysis and quantum chemical calculations [B3LYP/6-311G(d,p)] imply the stereospecific through-space stabilization of these cations by the oxime hydroxyl. [ABSTRACT FROM AUTHOR]

Abstract: О-2-(Acyl)vinylketoximes (freshly prepared from ketoximes and acylacetylenes in the presence of Ph3P as catalyst in up to 83% yields) rearrange upon heating (125–150°C) to give 2- or 3-acylpyrroles, wherein the positions of the acyl substituents do not correspond to known O-vinyloxime rearrangements; the chemo- and regioselectivity of the rearrangements depend on the reaction conditions. The described rearrangement enables syntheses of previously inaccessible substituted 2- or 3-acylpyrroles. [ABSTRACT FROM AUTHOR]

Rearrangement of 5-(1-vinyloxyiminoethyl)[2,2]paracyclophane, the key intermediate of the Trofimov reaction (pyrrole formation from ketoximes and acetylene), gives (120 °C, 30 min, DMSO) 2-([2,2]paracyclophan-5-yl)pyrrole in 74% yield. The intermediate 5-(1-vinyloxyiminoethyl)[2,2]paracyclophane has been synthesised in 78% yield by vinylation of the Cs-derivative of the oxime of 5-acetyl[2,2]paracyclophane with acetylene under pressure in the DMSO–n-pentane two-phase system (70 °C, 5 min). [Copyright &y& Elsevier]

Dioximes of hexane-2,5-dione and cyclohexane-1,4-dione react with acetylene in an autoclave (KOH/DMSO, 100 °C, 1 h, initial pressure 14 atm) to give 2,2′-dimethyl-1,1′-divinyl-[3,3′]bipyrrole and 1,5-divinyl-4,8-dihydropyrrolo[2,3-f]indole in 12% and 6% yields, respectively, thus exemplifying a very simple, straightforward route to inaccessible or unknown pyrrolic assemblies. [Copyright &y& Elsevier]

3-(1-Alkylthio-2-cyano-2-X-ethenyl)pyrroles (X=CN, CONH2, CO2Et) have been synthesized in 28–58% yields by the reaction of pyrrole-3-carbodithioates with CH-acids (malononitrile, cyanoacetamide, cyanoacetate) in the KOH–DMSO system. [Copyright &y& Elsevier]

Cyclohexyl phenyl and cyclohexyl (2-thienyl) ketoximes react with acetylene under pressure in the two-phase KOH/DMSO/ n -hexane system at 70 °C to afford the corresponding spirocyclic 3 H -pyrroles, 1-(het)aryl-2-azaspiro[4.5]deca-1,3-dienes, in 18–19% yields. [ABSTRACT FROM AUTHOR]

Isopropyl phenyl ketoxime reacts with acetylene in the KOH/DMSO suspension (atmospheric pressure, 90°C, 4h) to afford 3,3-dimethyl-2-phenyl-3H-pyrrole (30%) and 4,4-dimethyl-5-phenyl-1-vinyl-2-pyrrolidinone (5%) that is likely originated from 4,4-dimethyl-5-phenyl-3,4-dihydro-2H-pyrrol-2-ol as the key reaction intermediate. [ABSTRACT FROM AUTHOR]

Treatment of 1-(2-oxiranylmethyl)-4,5,6,7-tetrahydroindole with the DMF/(COCl)2 reagent system in CH2Cl2 (room temperature, 40min) starts oxirane opening to give 1-(3-chloro-2-hydroxypropyl)-4,5,6,7-tetrahydroindole followed by the formylation of the pyrrole ring to end up with the formation of 1-(3-chloro-2-formyloxypropyl)-4,5,6,7-tetrahydroindole-2-carboxaldehyde viathe intermediate 1-(3-chloro-2-hydroxypropyl)-4,5,6,7-tetrahydroindole-2-carboxaldehyde. [ABSTRACT FROM AUTHOR]

Various title compounds are obtained by highly efficient C-H butadiynylation of substituted pyrroles with halobutadiynes through simple grinding. [ABSTRACT FROM AUTHOR]

The article reports on a One-Pot Assembly from Isopropyl Phenyl Ketoxime and Acetylene During the Synthesis of 3H-Pyrrole (IV).

An abstract of the article "Superbase-Catalyzed [4 + 2] Cycloaddition of Acetylenes to 3,6-Di(pyrrol-2-yl)- -1,2,4,5-tetrazine: A Facile Synthesis of 3,6-Di(pyrrol-2-yl)pyridazines" by Boris A. Trofimov, Tatyana E. Glotova and colleagues is presented.