Pyrroles from ketoximes and acetylene. 46. Pyrroles with sterically hindered substituents

The corresponding pyrroles and their N-vinyl derivatives were obtained by the catalyzed (by an MOH-DMSO superbase) reaction of acetylene and its crypto forms (vinyl chloride, 1,2-dichloroethane) with alkyl-2,4-, alkyl-2,5-, and alkyl-3,4-dimethylphenylketoximes. Reaction intermediates — O-vinylketoximes — were detected.For Communication 45 See [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1320–1323, October, 1991.     

Sulfurization of polymers. 6. Poly(vinylene polysulfide), poly(thienothiophene), and related structures from polyacetylene and elemental sulfur

Polyacetylene obtained by the dehydrochlorination of polyvinyl chloride in the NaOH—DMSO system undergoes sulfurization with elemental sulfur at 120—300 °C to liberate hydrogen sulfide and to form electroconducting (0.7·10^–12—5.8·10^–15Sm nm^–1) and paramagnetic (1.5·10¹⁷—1.7·10¹⁹sp g^–1, g = 2.0035—2.0045, H= 0.44—0.66 mT) dark powders with a metallic luster. Their IR spectra and comparison with the samples of sulfurized polyethylene show that sulfurized polyacetylene contains poly(vinylene polysulfide), poly(thienothiophene), and related structures. The polymers afford the cathode discharge capacity of lithium batteries up to 950 mA h g^–1(in the first cycle) and stable cycling at a level of 500—300 mA h g^–1(25 cycles).     

1-Methyl-2(3,4)-(1-vinylpyrrol-2-yl)pyridinium iodides: some structural features revealed by 1H and 13C NMR spectroscopy

The reactions of 2-, 3-, and 4-(1-vinylpyrrol-2-yl)pyridines with methyl iodide afford the corresponding quaternary salts. Analysis of their ¹H and ¹³C NMR spectra showed that the quaternization of the nitrogen atom considerably enhances the -acceptor effect of the pyridine ring on the pyrrole ring and on the vinyl group. 1-Methyl-2-(1-vinylpyrrol-2-yl)pyridinium iodide contains no weak intramolecular C--H...N hydrogen bond present in the starting compound.     

Reactions of 1-vinyl-4,5,6,7-tetrahydroindole and its mixtures with 4,5,6,7-tetrahydroindole in the presence of Cr- and Pd-coated catalysts

In the presence of Cr- and Pd-coated -alumina catalysts, 1-vinyl-4,5,6,7-tetrahydroindole (VTHI) and its mixtures with 4,5,6,7-tetrahydroindole (THI) are converted into 1-ethyl-4,5,6,7-tetrahydroindole (1-ETHI), indole, and 2-ethylindole, in proportions dependent on the reaction conditions and the catalyst. Over a sulfided 1% Pd--alumina catalyst in the presence of hydrogen at 200°C, VTHI is converted into 1-ETHI and THI. When the temperature is raised to 300–350°C, indole is formed in addition to these products. A 11 mixture of VTHI and THI over 1% Pd--alumina at 300°C gives indole and 2-ethylindole, over a sulfided 1% Pd --alumina catalyst at 200°C, 1-ETHI, and over a Cr oxide catalyst at 500°C, indole.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1417–1422, June, 1991.     

Pyrimidines. 69. Syntheses based on acetylpyrimidines. Dipyrimidinyls and pyrimidine analogs of chalcone

Substituted pyrimidinyl styryl ketones were obtained by condensation of 4-methyl-2-phenyl-5-acetylpyrimidine with aromatic aldehydes, and their conformations in KBr and in solution in CHCl₃ were examined. 4,5-Dipyrimidinyl derivatives were obtained by cyclization of the pyrimidinyl styryl ketones with benzamine. The isomeric trioxo-4,5- and -4,6-dipyrimidinyls were obtained by reaction of 5- and 6-acetyluracils with benzalbisurea.See [1] for Communication 68.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 678–683, May, 1979.     

Pyrimidines

The reaction of methylenebisurea with 5-amino-1-R-pyrazoles and 3-ureido-1-phenylpyrazole gives 1- and 2-R-6-oxo-4,5,6,7-tetrahydropyrazolo[3,4-d]pyrimidines, respectively. The 1-R-6-oxo-4,5,6,7-tetrahydropyrazolo[3,4-d]pyrimidines are readily dehydrogenated to 1-R-6-hydroxypyrazolo[3,4-d]pyrimidines. The 2-R-6-oxo-4,5,6,7-tetrahydropyrazolo[3,4-d]pyrimidines could not be dehydrogenated.See [1] for communication XXXIV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1696–1699, December, 1972.     

Debugging Eukaryotic Genetic Code Expansion for Site‐Specific Click‐PAINT Super‐Resolution Microscopy

Super‐resolution microscopy (SRM) greatly benefits from the ability to install small photostable fluorescent labels into proteins. Genetic code expansion (GCE) technology addresses this demand, allowing the introduction of small labeling sites, in the form of uniquely reactive noncanonical amino acids (ncAAs), at any residue in a target protein. However, low incorporation efficiency of ncAAs and high background fluorescence limit its current SRM applications. Redirecting the subcellular localization of the pyrrolysine‐based GCE system for click chemistry, combined with DNA‐PAINT microscopy, enables the visualization of even low‐abundance proteins inside mammalian cells. This approach links a versatile, biocompatible, and potentially unbleachable labeling method with residue‐specific precision. Moreover, our reengineered GCE system eliminates untargeted background fluorescence and substantially boosts the expression yield, which is of general interest for enhanced protein engineering in eukaryotes using GCE.     

Novel BODIPY preparations from sterically hindered pyrroles. Synthesis and photophysical behavior in solution,polystyrene nanoparticles,and solid phase

Trimesityl-BODIPY (TMB), a new derivative of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene belonging to fluores-cent nanostructures series, was synthesized from the corresponding pyrrole by the Trofimov reaction. This reaction was also employed to obtain 2-[2.2]paracyclophanylpyrrole from 5-acetyl[2.2]-paracyclophane. The spectral properties of TMB have been investigated in dichloromethane, nanolatex (polystyrene) films prepared by rapid solvent evaporation, and microcrystals. Comparative analysis of TMB properties with those of mesityl-BODIPY (MB) was performed. TMB was prepared to minimize π-π interactions in order to preserve luminescence in the aggregate state. Both fluorophores were shown to form fluorescing aggregates in the amorphous state (film). Fluorescence spectra (extinction and lifetime) were also studied. In crystal, MB shows a weaker fluorescence, while TMB behaves as a single fluorescing aggregate with a lifetime of 9.5 ns.     

Pyrimidines. 71. Rearrangements of 2,2′,4-trimethoxy-6′-phenyl-4′,5-dipyrimidinyl to n-methyl oxo derivatives

A trimethoxy derivative with three nonequivalent methoxy groups was obtained from 2,2′, 4-trichloro-6′-phenyl-4′ 5-dipyrimidinyl. Rearrangement of 2,2′, 4-trimethoxy-6′-phenyl-4′, 5-dipyrimidinyl under Hubert-Johnson conditions and thermal rearrangement with and without a catalyst make it possible to obtain 2′,4-dimethoxy-1-methyl-2-oxo-and 2′-methoxy-1,3-dimethy1-2,4-dioxodipyrimidinyls and both tri-N-methyl isomers, viz., the 1,1′, 3-and 1,3,3′-trimethyl derivatives. The possibility of obtaining N-methyl derivatives of trioxodipyrimidinyl by methylation under various conditions was also examined. See [1] for communication 70. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 398–403, March, 1980.