Solution and solid-state studies of 3,4-dichloro-2,5-diamidopyrroles: formation of an unusual anionic narcissistic dimer

3,4-Dichoro-1H-pyrrole-2,5-dicarboxylic acid bis-phenylamide 3 and 3,4-dichoro-1H-pyrrole-2,5-dicarboxylic acid bis-butylamide 4 have been prepared and shown to deprotonate in the presence of basic anions: the X-ray crystal structure of the tetrabutylammonium salt of 3-H+ reveals the formation of a dimer in the solid state.     

Symmetric 3,4-Diacetyl-2,5-dimethoxypyrroles. Heterocyclization of 3,4-Diacetylhexane-2,5-dione with Primary Amines

Russian Journal of General Chemistry -     

The reaction of 2,5-dimethylpyrrole with O2(a1Δg) in the gas phase

The chemical reaction of 2,5-dimethylpyrrole (C₆H₉N) with O₂(¹Δ_g) was studied in the gas phase in an isothermal flow reactor at room temperature and low pressures. The C₆H₉N concentration profiles were studied under pseudo-first order conditions [C₆H₉N]_° ? [O₂(¹Δ_g)] with mass-spectrometric detection of C₆H₉N. O₂(¹Δ_g) was produced either in a microwave discharge or in a chemical reaction. The value for the rate constant: was measured. The rate constant is compared to the value obtained for the quenching process. The primary product C₆H₉NO₂ was detected by mass spectrometry and the reaction mechanism is proposed. The possibility of using this reaction as a gas phase titration reaction for O₂(¹Δ_g) is discussed.     

Synthesis and reactions of thiophene sulfides. Communication 40. An unusual reaction of 2,5-bis(methylthio)-3,4-bis(o-hydroxyphenyliminomethyl)thiophene

Conclusions In polar solvents (ethanol and chloroform), 2,5-bis(methylthio)-3,4-bis-(o-hydroxyphenyliminomethyl) thiophene undergoes intramolecular rearrangement to 2,5-bis(methylthio)-3-(2-benzoxazolyl)-4-(o-hydroxyphenylaminomethyl) thiophene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2750–2753, December, 1985.     

Reaction of 3,4-diiodo-2,5-dimethyl-1H-pyrrole with thioamides

3,4-Diiodo-2,5-dimethyl-1H-pyrrole reacted with thioacetamide in polar solvents or under solvent-free conditions to give 2,4,6-trimethyl-5H-pyrrolo[3,4-d][1,3]thiazole. The major product in the reaction of the title compound with thiobenzamide was 3,5-diphenyl-1,2,4-thiadiazole.     

Immobilization of Invertase in Copolymer of 2,5-Di(thiophen-2-yl)-1-p-Tolyl-1H-Pyrrole with Pyrrole

Immobilization of invertase in conducting copolymer matrix of 2,5-di(thiophen-2-yl)-1-p-tolyl-1H-pyrrole with pyrrole (poly(DDTP-co-Py)) was achieved via electrochemical polymerization. Kinetic parameters, Michaelis-Menten constant, K_m and the maximum reaction rate, V_max were investigated. Operational stability and temperature optimization of the enzyme electrodes were also examined.

Immobilized invertase reveals maximum activity at 50°C and; pH 8 and pH 4 for two copolymer matrices. Although the same two monomers are utilized for the copolymer synthesis, the way the copolymer is produced results in quite different responses in terms of enzyme activity, optimum pH and kinetic parameters. Excellent operational stability of the enzyme electrodes enables their repetitive use in the determination of invert sugar.     

Synthesis and mechanism of formation of novel 2,5-dihydro-2,5-diimino-3,4-di[(N,N-dimethylamino)methylideneamino]pyrroles and 5-amino-3,4-di[(N,N-dimethylamino)methylideneamino]-2H-2-iminopyrroles

Formation of 5-amino-3,4-di[(N,N-dimethylarnino)methylidenearnino]-2H-2-iminopyrroles 3 from the reaction of (Z)-N¹-(2-amino-1,2-dicyanovinyl)-N²-substituted-formamidines 1 with dimethylformamide diethyl acetal has been shown to occur by initial formation of (Z)-N¹-{l,2-dicyano-2-[N,N-dimethylamino)methylideneamino]vinyl}formamidines 8 (isolated), followed by base catalysed cyclisation and imi dazole ring opening by dimethyl amine. The kinetic product of the ring opening reaction is the 2,5-diimino2,5-dihydropyrrole derivatives 11, which have been isolated and characterized spectroscopically and by a single crystal X-ray analysis on the R = Ph derivative. In solution at room temperature the N-aryl derivatives undergo a rapid Dimroth rearrangement to give the thermodynamic ally more stable isomer 3 , but compound 11 (R = Me) is much more stable in solution.     

Addition reactions of heterocycles. VI. Reactions of 1,2-dimethylpyrrole and 1-methyl-2-carbomethoxypyrrole with nitrilimines

Addition reactions of 1,2-dimethylpyrrole and 1-methyl-2-carbomethoxypyrrole with C-acetyl-N-phenylnitrilimine, have been investigated. 1,2-Dimethylpyrrole gives three different types of adducts: i.e. bis-cycloadducts (Vc) and (VIc), spirocycloadduct (IX), and non cyclic bis-adduct (XII). On the other hand, 1-methyl-2-carbomethoxypyrrole gives the bis-cycloadduct (VIb) only. Compound XII arises probably through a double 1,3-addition reaction, whereas the formation of cycloadducts Vc, VIc, and IX depends on the substituents present at C₂ of the pyrrole ring and consequentially on the intermediary occurence of mono-cycloadduct (IIIc), its methylenic tautomer VII, VIc, and XL The behaviour of the cycloadducts towards heating or acidic treatment showed a termal cleavage of the pyrazoline ring and acidic cleavage of the pyrrolidine ring.     

Reactivity of pyrrole pigments. part 6: Electrochemical reduction of some s(1h)-pyrromethenones and 5-arylmethylene-3,4-dimethyl-3-pyrrolin-2-ones

The electrochemical reduction of some 5(1H)-pyrromethenones and 5-arylmethylene-3-pyrrolin-2-ones in imethylformamide (DMF) has been studied by polarography and by identification of their electrochemical reduction products. The reduction processes observed depend on the presence on the type of supporting electrolyte. LiClO₄ or tetraethyl ammonium perchlorate (TEAP) and, When TEAP is used, they also depend on the presence of Water. Polarographic curves show two monoelectronic diffusion Waves in anhydrous DMF both with LiCIO₄ and with TEAP. The reaction products from (Z)-3,4-dimethyl-5-[(4-methylphenyl)methylene]-3-pyrrolin-2-one and from (Z)-2-[(3,4-dimethyl-5-oxo-3-pyrrolin-2-yl)-methylene]-1H-pyrrole for the electrolysis at controlled potentials and under different experimental conditions have been isolated and identified.In all cases a stereoselective reductive dimerization occurs but, at second wave potentials, the reduction compounds corresponding to the hydrogenation of the exocyclic double bond are also formed. The electrolysis yields can be optimized in order to make the process synthetically useful.     

Reactivity studies of a disilene with N2O and elemental sulfur

In a previous contribution, we have reported on a convenient and high yield synthesis of the disilene trans-[(TMS)(2)N(η(1)-Me(5)C(5))Si═Si(η(1)-Me(5)C(5))N(TMS)(2)] (2). Herein, we show the reactions of 2 with N(2)O and S(8). The former reaction affords two isomeric (cis- and trans-) dioxadisiletane ring compounds. To the best of our knowledge, this is the first report where both cis-and trans-isomers are isolated from the same disilene precursor and characterized structurally by single-crystal X-ray diffraction (XRD) studies. The reaction of 2 with elemental sulfur yields only the trans-isomer. To investigate this dissimilar reaction pattern exhibited by 2, computational studies were performed. Density functional theory (DFT) calculations showed that the two dioxadisiletane ring isomers are isoenergetic, with the trans isomer being slightly more stable than the cis counterpart, by 3.3 kcal/mol, while that is not the case with sulfur. All the isolated compounds are characterized by single-crystal XRD studies, multinuclear NMR spectroscopy, and electron ionization-mass spectrometry (EI-MS).     

On the reaction of diethyl 3,4-dihydroxythiophene-2,5-dicarboxylate with 1,2-dibromoethane

Summary Reaction of diethyl 3,4-dihydroxythiophene-2,5-dicarboxylate (1) with an excess of 1,2-dibromoethane afforded a mixture of the 2,3-dihydrothieno[3,4-b] [1,4]-dioxine-derivative3 and the 3-oxo-2,3-dihydrothiophene4. Compounds3 and4 were characterized by spectroscopic methods.

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Zur Reaktion von 3,4-Dihydroxythiophen-2,5-dicarbonsäurediethylester mit 1,2-Dibromethan (Kurze Mitt.)

Zusammenfassung Die Reaktion von 3,4-Dihydroxythiophen-2,5-dicarbonsäureethylester (1) mit einem Überschuß an 1,2-Dibromethan führt zur Bildung des 2,3-Dihydrothieno[3,4-b] [1,4]dioxin-Derivats3 und des 3-Oxo-2,3-dihydrothiophens4. Die Struktur der Verbindungen3 und4 wurde mit Hilfe spektroskopischer Methoden ermittelt.

     

Reactivity of 2-halo-2H-azirines. 1. Reactions with nucleophiles.

Nucleophilic substitution reactions of 2-halo-2H-azirines 1a, 1b, 1d, and 1e with potassium phthalimide and aniline allowed the preparation of new substituted 2H-azirines 2-5. The reactions of 2-bromo-2H-azirine 1a with methylamine led to the synthesis of alpha-diimines 7 and 8. 2-Halo-2H-azirines were also established as building blocks for the synthesis of a range of heterocyclic compounds, namely, quinoxalines 10a-10d, 3-oxazoline 14, and 2H-[1,4]oxazines 18 and 20. X-ray crystal structures of alpha-diimine 7, 3-oxazoline 14, and 2H-[1,4]oxazine 18 are reported.     

Pyrrole studies—XXIV: The reactions of 1-methyl-2-vinylpyrrole and 1-phenyl-2-vinylpyrrole with dimethyl acetylenedicarboxylate

The reaction of dimethyl acetylenedicarboxylate with 1-methyl-2-vinylpyrrole is temperature dependent. At 80° the predominant reaction is the [4π + 2π] cycloaddition to give dimethyl 1-methyl-6,7-dihydroindole-4, 5-dicarboxylate, whereas at room temperature Michael addition of the acetylenic ester at the 5-position of the pyrrole ring to give fumaric and maleic ester derivatives also occurs. Unequivocal assignment of the configurations of the Michael adducts have been made on the basis of their ³J_CO,h coupling constants. 1-Phenyl-2-vinylpyrrole reacts with dimethyl acetylenedicarboxylate to give only the [4π + 2π] cycloadduct at room temperature and at elevated temperatures.     

Pyridazines. LIX. An unusual reaction of azidoazolopyridazines with diethylamine

6-Azidoazolopyridazines and 6-azidopyridotetrazolopyridazines react in the presence of diethylamine to give various products. Among them, the corresponding diethylaminomethylene-amino derivatives were formed in a novel reaction.