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An efficient method for the synthesis of pharmaceutically prospective pyrrole-aminopyrimidine ensembles (in up to 91% yield) by the cyclocondensation of easily available acylethynylpyrroles with guanidine nitrate has been developed. The reaction proceeds under heating (110-115 °C, 4 h) in the KOH/DMSO system. In the case of 2-benzoylethynylpyrrole, the unexpected addition of the formed pyrrole-aminopyrimidine as N- (NH moiety of the pyrrole ring) and C- (CH of aminopyrimidine) nucleophiles to the triple bond is observed.

Available pyrrolylalkynones with tetrahydroindolyl, cycloalkanopyrrolyl, and dihydrobenzo[g]indolyl moieties, acylethynylcycloalka[b]pyrroles, are readily annulated with Δ1-pyrrolines (MeCN/THF, 70 °C, 8 h) to afford a series of novel pyrrolo[1′,2′:2,3]imidazo[1,5-a]indoles and cyclohepta[4,5]pyrrolo[1,2-c]pyrrolo[1,2-a]imidazoles functionalized with an acylethenyl group in up to an 81% yield. This original synthetic approach contributes to the arsenal of chemical methods promoting drug discovery. Photophysical studies show that some of the synthesized compounds, e.g., benzo[g]pyrroloimidazoindoles, are prospective candidates for TADF emitters of OLED. [ABSTRACT FROM AUTHOR]

A novel strategy for the synthesis of 4-amino-3-cyano-2,2′- and 5′-amino-4′-cyano-2,3′-bipyrroles via readily available 1-amino-3-imino-3 H -pyrrolizine-2-carbonitriles has been developed. The rearrangement leading to 5′-amino-4′-cyano-2,3′-bipyrroles involves formation of the intermediate aziridine, which undergoes other side ring-opening. [ABSTRACT FROM AUTHOR]

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]

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]

Acetylene in the KOH / DMSO system (1 bar, 140 °C, 12 h) is annulated with 3-methyl-7,8-dihydrocinnolin-5(6 H )-one oxime in several directions: along with the building up of pyrrole fragment over cyclohexane ring, transformation of the oxime function to the amino one occurs. This amine undergoes other annulations to form tricyclic compounds with pyridine moieties. [ABSTRACT FROM AUTHOR]

[Display omitted] Methods for the preparation of two highly flexible synthetic building blocks, namely pyrrole/aminoenone and pyrrole/aminoacrylonitrile ensembles, on the basis of available starting materials such as 2-acylethynylpyrroles or pyrrole-2-carbodithioates, are summarized. The presence of several reactive centers in their molecules (pyrrole ring, enamine and carbonyl or nitrile moieties) ensures their multiple reactivity and application as versatile intermediates in the synthesis of heterocyclic ensembles such as pyrrolyl pyridines, bipyrroles, pyrrolyl-isoxazoles and condensed compounds, such as pyrrolo[3,2- a ]pyrazines, pyrrolizines, which have high potential for use in medical chemistry and materials science. [ABSTRACT FROM AUTHOR]

The recyclization of readily available 1-(benzoylmethylanilino)-3-imino-3 H -2-cyanopyrrolizines using the DBU organic superbase, unexpectedly gave 2,2′-bipyrroles with amino, keto and cyano functional groups on one of the pyrrole rings in 83–94% yield. Previously, using the KOH/DMSO system, this recyclization led to 2,3′-bipyrroles in low yields (12–26%). This selective switching was explained by sterically hindered access for the intermediate carbanion to the 1-position of the pyrrolizine ring due to the large size of the accompanying DBU countercation. The new methodology opens an efficient route to pharmaceutically and synthetically useful densely functionalized 2,2′-bipyrroles. [ABSTRACT FROM AUTHOR]

Graphical abstract 6,7-Dihydrobenzo[ c ][1,2,5]oxadiazol-4(5 H)-one oxime is annelated with acetylene in the KOH/DMSO/H 2 O system under pressure to give NH - or N -vinyl-5,8-dihydro-4 H -[1,2,5]oxadiazolo[3,4- g ]indoles in 29 and 68% yields, respectively. These derivatives are readily aromatized with DDQ at room temperature to the expected indoles. [ABSTRACT FROM AUTHOR]

• AlCl 3 is the new effective catalyst for the synthesis of asymmetric meso -CF 3 -dipyrromethanes. • Approach to new dipyrromethanes – precursors of BODIPY dyes and metal complexes – was described. • Excess of catalyst could cause disproportionation. Asymmetric meso -CF 3 -dipyrromethanes with amino- and nitrogen heterocyclic functions, a new family of the BODIPY dye precursors, have been synthesized in 70–90 % yield by condensation of trifluoro(pyrrolyl)ethanols with pyrroles in the presence of AlCl 3. This catalyst, for the first time, was shown to be more efficient than commonly used P 2 O 5 , which was entirely inactive in the condensation of pyrroles having basic substituents (amino group and pyrazole moiety). [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: 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]