Effect of Organic Compounds and Salts on the Tris(2,2"-Bipyridyl)Ruthenium(II)-Photosensitized Substitution of the Sulfo Group for Halogen in Halogenated Naphthalenes in Aqueous Solutions

The effect of the addition of organic compounds and salts on the occurrence of the chain radical-ion reaction of replacement of halogen by sulfo group in halogenated hydroxynaphthalenes in a sodium sulfite aqueous solution, which was photosensitized by a tris(2,2"-bipyridyl)ruthenium(II) complex, was studied. It was shown that both organic compounds and salts in small concentrations increase the quantum yield of the substitution reaction. The kinetic scheme of the reaction is discussed.     

The salt effect on riboflavin-photosensitized substitution of the sulfo group for bromine in 1-bromo-2-hydroxynaphthalene

It was shown that the substitution reaction of the sulfo group for bromine in 1-bromo-2-hydroxynaphthalene photosensitized with riboflavin occurred via the riboflavin triplet state. Electron-donor anions quench the fluorescence of riboflavin. Halide (iodide and bromide) ions increase the quantum yield of the substitution reaction at low concentrations because of an increase in the spin-orbital coupling in the radical ion pair generated in riboflavin fluorescence quenching. As a result of the spin-orbital conversion, the triplet-state radical ion pair is formed, which separates into the riboflavin radical anion and the halogen atom. The halogen atom is reduced by the sulfite ions with the simultaneous formation of the sulfite radical anions, which participate in the propagation of the substitution reaction chain. All salts increase the quantum yield of the substitution reaction at high concentrations (>0.5 mol l^?1).     

Magnetic Field Effect on the Quantum Yield of the Chain Reaction of Sulfo Group Photosubstitution for Bromine in 1-Bromo-2-Hydroxynaphthalene

It has been shown that the quantum yield of the photochemical reaction of bromine replacement by the sulfo group in 1-bromo-2-hydroxynaphthalene decreases with an increase in the magnetic flux density. The participation of the triplet radical ion pair in the initiation of the chain photosubstitution reaction was directly confirmed. The lifetime of the radical ion pair was estimated.     

Riboflavin-sensitized photochemical radical ion chain reaction of sulfo-group substitution for halogen in halogenated hydroxynaphthalenes

It was shown that riboflavin (RF) is a sensitizer for the radical ion chain reaction of sulfo group substitution for halogen in halogenated hydroxynaphthalenes. The initaition mechanism involves the electron transfer reaction between the sulfite ion and excited riboflavin. The quantum yields of RF radical anions from the singlet and the triplet states upon excitation in an aqueous sodium sulfite solution are 0.01 and 0.15, respectively, as determined by means of flash photolysis. The principal decay reaction for RF radical anions is their recombination with sulfite radical anions in the bulk of solution at a rate constant of (3.8 ± 0.5) × 10⁹ dm³ mol^?1 s^?1. The quantum yields of the riboflavin-sensitized substitution reaction increases in the presence of electron scavengers (chloranil, dinitrobenzene) and inorganic salts in the system.     

Effect of Nitrate Ions on the Chain Photochemical Reaction of Sulfo Group Substitution for Bromine in 1-Bromo-2-Hydroxynaphthalene upon Sensitized and Direct Photolysis

The influence of nitrate ion admixtures on the proceeding of the radical-ion chain reaction of sulfo group substitution for halogen in halogenated hydroxynaphthalenes in an aqueous sodium sulfite solution was studied upon both direct and tris(2,2-bipyridyl)ruthenium(II)-sensitized photolysis. It was found that nitrate ions increase the quantum yields of the photosensitized substitution reaction and decrease the quantum yields of the reaction in the direct photolysis. Based on an analysis of kinetic schemes of the reaction, it was shown that nitrate ions affect the photoinitiation step in sensitized photolysis or the termination step in the direct photolysis.     

Halogen substitution reaction in bromonaphtol and iodophenol photoinitiated by aromatic amines

An increase in quantum yield in the halogen photosubstitution reaction upon the photolysis of 1-bromo-2-naphtol and o-iodophenol by the sulfo group in aqueous sodium sulfite solution or by the hydrogen in organic solvents in the presence of aromatic amines (diphenylamine, carbazole) was observed. Quenching of the triplet 1-bromo-2-naphtol by diphenylamine with the rate constant 7 × 10⁷ M¹ s¹ was discovered with the help of flash photolysis. The photoinitiation mechanism of the substitution reaction is due to electron transfer.     

Peculiarities in the photochemical behavior of 1-bromo-2-hydroxynaphthalene in cetylpyridinium chloride micellar solution

Unlike the case of aqueous solution, two products are formed in the photolysis of 1-bromo-2-hydroxynaphthalene in a cetylpyridinium chloride micellar solution in the presence of sodium sulfite. These products are formed as a result of competitive steps of the primary photochemical process, the C–Br bond photodissociation and the heterolytic dissociation with elimination of the bromide anion. The bond photodissociation results in the product of bromine replacement by the sulfo group. The heterolytic dissociation affords the dimerization product. In the micellar solution, the iodide ions increase the quantum yield of the photosubstitution product due to the heavy atom effect and do not affect the quantum yield of the dimerization product. The halogenated derivatives of hydroxynaphthalene in micelles do not fluoresce in a neutral or alkaline medium.     

Synthesis of <Emphasis Type="Italic">N</Emphasis>-vinylazole polymers via chemical modification of poly(vinyl halides)

The formation of azole-containing polymers via nucleophilic substitution of a halogen in poly(vinyl halides) with an azole group with the use of salts of different azoles as reagents has been investigated. The maximal degree of azolation is achieved via the interaction of polymer substrates with the sodium salt of 4-nitro-1,2,3-triazole. Simultaneously with substitution of the halogen with the azole fragment, dehydrohalogenation inevitably proceeds under reaction conditions. The intensity of both processes substantially depends on the basicity of an azolate anion, temperature, and reaction duration.     

7-Dialkylamino-1-alkylquinolinium salts: highly versatile and stable fluorescent probes

7-Dialkylamino- and 7-alkylsulfenyl-1-alkylquinolinium salts have been synthesized using a novel synthetic approach. The key intermediate, 7-fluoro-1-methylquinolinium iodide, was shown to possess high reactivity toward nitrogen and sulfur nucleophiles, and the kinetics of this nucleophilic aromatic substitution reaction was investigated. A wide variety of compounds were synthesized and characterized spectroscopically. High fluorescence quantum yields were observed, and this was attributed to the rigid molecular architecture. The thermal and photochemical stability of a number of compounds was investigated, and it was demonstrated that 7-dialkylamino-1-methylquinolinium salts have superior stability compared to a number of hemicyanine dyes and rigid charge-transfer probes. Based on the high quantum yields, the large Stokes shifts, and in particular, the high thermal and photochemical stability, it is concluded that 7-dialkylamino-1-methylquinolinium salts are excellent color-shifting, mobility-sensitive fluorescent probes for polymer characterization and other demanding applications.     

MICROWAVE INDUCED SYNTHESIS OF COUMARINS FROM IN SITU GENERATED STABILIZED PHOSPHORUS YLIDES IN THE PRESENCE OF SILICA GEL POWDER IN SOLVENT-FREE CONDITIONS

Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates, by phenols (1-hydroxynaphthalene, 2-hydroxynaphthalene and 4-bromophenol) leads to vinyltriphenylphosphonium salts, which undergo aromatic electrophilic substitution reaction with conjugate base to produce corresponding stabilized phosphorus ylides. Microwave was found to catalyze conversion of the stabilized phosphorus ylides to corresponding coumarins in the presence of silica gel powder in solvent-free conditions.     

Photoinduced Atom Transfer Radical Addition/Cyclization Reaction between Alkynes or Alkenes with Unsaturated α-Halogenated Carbonyls

We have developed a photochemical ATRA/ATRC reaction that is mediated by halogen bonding interactions. This reaction is caused by the reaction of malonic acid ester derivatives containing bromine or iodine with unsaturated compounds such as alkenes and alkynes in the presence of diisopropylethylamine under visible light irradiation. As a result of various control experiments, it was found that the formation of complexes between amines and halogens by halogen-bonding interaction occurs in the reaction system, followed by the cleavage of the carbon–halogen bonds by visible light, resulting in the formation of carbon radicals. In this reaction, a variety of substrates can be used, and the products, cyclopentenes and cyclopentanes, were obtained by intermolecular addition and intramolecular cyclization.     

Reactions of organic anions—L : Reactions of phenylacetonitrile derivatives with aromatic nitrocompounds in basic media

Reaction of phenylalkanenitriles and diphenylacetonitrile with aromatic nitro compounds were studied using various base-solvent systems. Four independent types of reaction: substitution of halogen, substitution of nitro group, substitution of hydride anion and electron transfer were observed. Relationship—reaction pathway—conditions have been discussed.     

CONVERSION OF IN SITU GENERATED STABILIZED PHOSPHORUS YLIDES TO CHROMENE DERIVATIVES IN SOLVENT-FREE CONDITIONS

Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates, by phenols (1-hydroxynaphthalene, 2-hydroxynaphthalene, 4-bromophenol, 2-hydroxybenzaldehyde, and 5-bromo-2-hydroxyben- zaldehyde) leads to vinyltriphenylphosphonium salts, which undergo electrophilic substitution reaction with conjugate base to produce corresponding stabilized phosphorus ylides. Microwave was found to catalyze conversion of the stabilized phosphorus ylides to chromene derivatives in the presence of solid catalysts in solvent-free conditions at microwave power 0.4 KW in 3 min.     

Photolysis of <Emphasis Type="Italic">p</Emphasis>-benzoquinone and <Emphasis Type="Italic">p</Emphasis>-chloranil in aqueous sodium sulfite solution

Photosubstitution of the sulfo group for hydrogen (chlorine in chloranil) is observed under irradiation of sulfonated derivatives of hydroquinone formed upon dissolving of p-benzoquinone and p-chloranil in aqueous solutions of sodium sulfite. The quantum yield of the photochemical reaction is 0.18 ± 0.02 for p-benzoquinone. The rate constant of the thermal reaction of substitution is 5.5 × 10⁻⁴ l mol⁻¹ s⁻¹. The substitution reaction is sensitized by eosin upon irradiation with visible light. During the course of irradiation of sulfohydroquinones, the formation of a product with an absorption maximum at 235 nm was found. The product decays with a rate constant of 0.005 s⁻¹.     

Study of photopolymers. XVI. Novel syntheses of the polymers with azidonitrobenzoyl groups and their photochemical and thermochemical reactions

Poly-2-(2-azido-5-nitrobenzoyloxy)ethylmethacrylate (P-II-A) and poly-2-(4-azido-3-nitrobenzoyloxy)ethylmethacrylate (P-II-B) were synthesized from the reactions of 2-hydroxyethylmethacrylate with 2-chloro-5-nitrobenzoic acid and 4-chloro-3-nitrobenzoic acid, respectively, by substitution reactions of sodium azide with the corresponding chloronitrobenzoyl group. In addition, the degradation reaction of the 2-azido-5-nitrobenzoyl group in P-II-A and the transformation of the 4-azido-3-nitrobenzoyl group to 5-carboxylbenzofurazane-1-oxide ring in P-II-B by irradiation with ultraviolet (UV) light or by heating were investigated in detail. In the photochemical reaction the reaction of the azide group in P-II-A was affected by the presence of a spacer in the polymer chain. Moreover, in the thermochemical reaction the rates of the reactions of azide groups in P-II-A and P-II-B were controlled by the facility of molecular motion and the conformation of polymer chains.     

The synthesis and the solvent and substituent effect on the spectroscopic characteristic of 3-ethyl-2-(p-substitued styryl)benzothiazolium iodides

The photophysical and photochemical properties of p-substitued 2-styryl-ethylbenzothiazolium iodides, possessing different electron-withdrawing or electron-donating groups are described. The dyes were prepared by the condensation of 3-ethyl-2-methylbenzothiazole salts with p-substituted benzaldehydes. The synthesis of suitable substrates is presented as well. We describe here the absorption, emission spectra and the luminescence quantum yield of hemicyanine dyes (SH) measured in 11 different organic solvents of varying polarity. Molecular structure of the synthesized dyes was established by (1)H NMR, electronic absorption and fluorescence spectrometry. The spectral data confirmed that all the compounds exist in E-configuration of their styryl residues. The planar molecular conformation is typical for the compounds with five-membered side aromatic moieties (for example benzothiazole). The compounds possessing N-alkyl substituent in phenyl ring, in contrast to the compounds with other substituents, exhibit low fluorescence quantum yield in THF solution. This indicates that for N-alkyl derivatives the non-radiative processes are much more effective than the radiative ones. The electronic absorption and fluorescence emission spectra of tested dyes demonstrate high sensitivity to the nature of substituent introduced into the aromatic ring.     

Preparation of 6-chloro-6-desoxy- and 6-iodo-6-desoxycellulose

Conclusions The reaction of 2,3-di-O-acetylcellulose with N-chloro- or N-iodosuccinimide and triphenylphosphine gave the 6-chloro-6-desoxy- and 6-iodo-6-desoxycellulose acetates with a respective degree of substitution (DS) in halogen of 0.8–1.0 and 0.7. The deacetylation of these compounds gave 6-chloro-6-desoxycellulose (DS 0.8) and 6-iodo-6-desoxycellulose (DS 0.6).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2158–2160, September, 1977.     

‘On water’ synthesis of 2,4-diaryl-2,3-dihydro-1,5-benzothiazepines catalysed by sodium dodecyl sulfate (SDS)

An efficient synthesis of 1,3-diaryl-2,3-dihydro-1,5-benzothiazepines has been developed by the reaction of various 1,3-diaryl-2-propenones with 2-aminothiophenol in water under neutral conditions catalysed by SDS. Excellent chemoselectivity was observed for substrates possessing halogen atoms or nitro/alkoxy/thioalkyl groups which did not undergo competitive aromatic nucleophilic substitution of the halogen atoms or the nitro group, reduction of the nitro or the α,β-unsaturated carbonyl group, or dealkylation of the alkoxy/thioalkoxy groups.     

Prediction of the molar volume at the normal boiling point

A group contribution method for the prediction of the molar volume at the normal boiling point has been developed. The method can be used for organic and inorganic compounds. It cannot be used for elements and diatomic molecules. Group contributions are shown for a wide variety of hydrocarbons, organic halogen compounds, organic oxygen compounds, organic nitrogen compounds, organic sulfur compounds, organic boron compounds, organic silicon compounds, miscellaneous organics, and many inorganic compounds.Contrary to the corresponding states methods for the prediction of molar volumes, knowledge of critical properties, acentric factors, and reference volumes is not needed.     

Nucleophilic 18F-fluorination of heteroaromatic iodonium salts with no-carrier-added [18F]fluoride

Diaryliodonium salts containing the 2-thienyl group as an example of an electron-rich heteroaromatic moiety proved to be very potent precursors for the nucleophilic, regioselective no-carrier-added (nca) radiofluorination of various arenes. It even allowed the nucleophilic introduction of nca [18F]fluoride into electron-rich arene compounds in one step. The influences of the substitution pattern, of counteranions, and of different reaction conditions were studied. Effects of counterions could be explained by the influence of solvent on ion pair separation of precursor salts. Different aryl(2-thienyl)iodonium salts were used as precursors, where the homoaromatic group systematically varied from bearing electron-deficient to electron-rich substituents. Relative rates of exchange kinetics correlated linearly with Hammett constants of the appropriate substituents confirming a nucleophilic aromatic substitution reaction of high reactivity and low selectivity.