I. I. Levina

Regioselective Synthesis and Structure of New Oligophosphorylated rctt Resorcinarenes

Abstract Regioselective phosphorylation of rctt tetranaphthyl resorcinarenes gave monofunctionalized derivatives with eight phosphamide groups immobilized on the macrocyclic matrix, as well as heterofunctionalized derivatives containing hydroxyl groups on the vertically oriented benzene rings and phosphorus fragments on the planar benzene rings. GRAPHICAL ABSTRACT

Studies of photoinduced addition of water and alcohols to substituted dihydroquinolines

Steady-state photolysis products of 6- and 8-substituted 2,2,4-trimethyl-1,2-dihydroquinolines in water and lower alcohols were identified by 1H NMR. In the case of electron-donor substituents, the solvent molecule is added to the double bond of the heterocycle affording the corresponding 4-hydroxy- or 4-alkoxytetrahydroquinolines. Nitro-substituted dihydroquinolines are photostable. The addition of EtOH and PrnOH occurs only in the presence of water to give a mixture of alkoxy- and hydroxy-adducts. A reaction scheme is suggested.

Lewis Acid Triggered Vinylcyclopropane–Cyclopentene Rearrangement

We report a mild Lewis acid induced isomerization of donor-acceptor cyclopropanes, containing an alkenyl moiety and diverse electron-withdrawing group(s) at the adjacent positions, into substituted cyclopentenes. We have found that 1,1,2-trisubstituted cyclopent-3-enes were exclusively obtained in yield of 51-99% when cyclopropanes with a 2-substituted alkenyl group as a donor underwent isomerization. For cyclopropanes bearing a trisubstituted alkenyl group either the corresponding cyclopent-3-enes or isomeric cyclopent-2-enes having two acceptor groups at the C(1) atom were formed, with the reaction selectivity being determined by the applied Lewis acid. We have shown that the reactivity of the donor-acceptor cyclopropane increases with the increase of the electron-donating character of (hetero)aromatic group attached to the alkenyl moiety. The synthetic utility of the developed methodology was also demonstrated through the synthesis of polysubstituted cyclopentane and piperidine derivatives.

Synthesis of per-6-О-(tert-butyl)(diphenyl)silyl-β-cyclodextrin

Per-6-O-(tert-butyl)(diphenyl)silyl-β-silylcyclodextrin has been obtained regioselectively via the reaction with tert-butyldiphenylchlorosilane. Further treatment of the product with chlorosilanes has led to the corresponding derivatives of β-cyclodextrin with mixed silyl groups at the primary hydroxyl groups.

Spectral and time-resolved properties of novel hetarylazo dyes containing hydrogenated quinolines and triazole moieties

The spectral characteristics of novel hetarylazo dyes containing triazole and hydrogenated quinoline moieties and the spectral and time-resolved parameters of photochemical processes occurring upon their photoexcitation were studied by stationary spectrophotometry and pulse photolysis. All compounds have an intense absorption maximum in the visible spectral range at 470–500 nm with ɛ = 17000–27000 L mol−1 cm−1. Upon excitation with the visible light, reversible trans-cis photoisomerization occurs, which is followed by thermal cis-trans isomerization. The temporal parameters of the isomerization depend on the azo dye structure. The introduction of bulky substituents in the triazole and hydroquinoline moieties results in the increase in characteristic times of the thermal transformation of the generated transient species from milliseconds to seconds and in the partial irreversibility of the process.

Hydrophosphorylation of monosaccharides oximes and hydrazones

The hydrophosphorylation of monosaccharides oximes and hydrazones was studied; similarity and difference of this process compared to the reaction of secondary glycosylamines with the hydrophosphoryl compounds are shown. A number of the original α-aminophosphoryl compounds is obtained including those containing carbohydrate fragment in their compositions.

Role of steric hindrance in photoinduced proton transfer from solvent to excited molecules of 1,2-dihydroquinolines

It was shown that the photolysis of 1,2,6-trimethyl-1,2-dihydroquinoline (126TMDHQ) in water, methanol, ethanol, and isopropanol affords the corresponding adducts of water and the alcohols, unlike the case of 2,2,4-trimethyl-1,2-dihydroquinolines bearing the methyl, alkoxyl, and hydroxyl substituents in the 1-, 6-, and 8-positions, which were previously found to form adducts only in the presence of water and MeOH. The quantum yield of the 126TMDQ photolysis (Φ) in this solvent series changes as ΦMeOH:ΦEtOH:ΦPrOH = 10:3:1. The results were rationalized in terms of the effect of steric hindrance caused by substituents on the heterocycle and increasing size of the alcohol alkyl group on proton transfer from the solvent to the 1,2-dihydroquinoline molecule in the excited singlet state. The existence of two adduct isomers was revealed. The preferential formation of one of the isomers was considered from the standpoint of carbocation accessibility to the solvent by nucleophilic attack.

Dual reactivity of an intermediate cation formed in the photolysis of dihydroquinolines in methanol

Photolysis of 2,2,4,6-tetramethyl- (1) and 1,2,2,4,6-pentamethyl-1,2-dihydroquinoline (2) in methanolic alkali yields only 4-methoxy-2,2,4,6-tetramethyl-1,2,3,4-tetrahydroquinoline in the former case and a mixture of 4-methoxy- and 4-hydroxy-1,2,2,4,6-pentamethyl-1,2,3,4-tetrahydroquinoline in the latter case. This result was rationalized by the existence of two resonance structures of an intermediate cation, viz., carbocationic and ortho-quinomethaneiminium species. The cation from 1 reacts with an alkali in the ortho-quinomethaneiminium form, and the cation generated from 2 reacts in the carbocationic form.

Photoaddition of water and methanol to 2,2,4,6-tetramethyl-1,2-dihydroquinoline

Products of the steady-state photolysis of 2,2,4,6-tetramethyl-1,2-dihydroquinoline (1) in water, methanol, and water—ethanol were isolated for the first time and identified by1H and13C NMR spectroscopy, IR spectroscopy, and mass spectrometry. As a result of the photolysis, the molecule of the solvent is added to the double bond of the heterocycle with formation of 4-hydroxy- (2) or 4-methoxy-2,2,4,6-tetramethyl-1,2,3,4-tetrahydroquinoline (3) in water and methanol, respectively. Compounds2 and3 are converted gradually into1 in the dark. The rate of the back reaction depends on the solvent and the concentration of the product. Comparison of the products of the photolysis in methanol and hexane at 45 °C and of the azoisobutyronitrile-initiated oxidation of1 at the same temperature has shown that unlike the photolysis in hexane, aminyl radicals are not precursors of the product of the photolysis in methanol. The reaction proceedsvia an excited singlet state.

Convenient approach to polyoxygenated dibenzo[c,e]pyrrolo[1,2-a]azepines from donor–acceptor cyclopropanes

A short convenient approach to polyoxygenated tetrahydrodibenzo[c,e]pyrrolo[1,2-a]azepines from the donor–acceptor cyclopropanes was developed. A simple synthetic sequence involves: (a) cyclopropane ring opening with azide ion and Krapcho dealkoxycarbonylation; (b) azide-to-imine transformation followed by imine reduction; (c) the oxidative cyclization of 5-aryl-1-benzylpyrrolidin-2-ones, the key intermediates for this approach.