Determination of the structure of 7-diethylamino-4-(1,2,3-triazol-1-yl)-2H-1-benzopyran-2-one derivatives using two-dimensional heteronuclear chemical-shift correlated NMR techniques

¹H and¹³C NMR spectra of 7-diethylamino-4-(1,2,3-triazol-1-yl)-2H-1-benzopyran-2-one derivatives have been studied. The location of the substituent in the 1,2,3-triazole ring was determined by the 2D COLOC method. It was established that the H(3) and H(5) protons in the coumarin moiety experience anisotropic influence of the phenyl subsituent at the C(5) atom in the triazole ring.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1330–1332, July, 1994.     

<Emphasis Type="Italic">tert</Emphasis>-Butyl (2<Emphasis Type="Italic">S</Emphasis>)-(<Emphasis Type="Italic">p</Emphasis>-tolylsulfonyloxy)propionate — a suitable reagent for the direct alkylation of indole derivatives

A new method is proposed for the synthesis of indole derivatives containing a chiral substituent at the nitrogen atom, which includes the direct alkylation of indole derivatives with tert-butyl (2S)-(p-tolylsulfonyloxy)propionate, obtained from commercial ethyl (S)-lactate with subsequent conversion to the corresponding p-toluenesulfonyloxy derivative by hydrolysis, and esterification. Dedicated to Academician B. A. Trofimov on his 70^th birthday. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, 1391–1398, September, 2008.     

First asymmetric synthesis of 4-piperidones. Preparation of optically active diastereomers of 1-α-phenylethyl-2-methyl-4-piperidone

The fundamental possibility of carrying out the asymmetric synthesis of 4-piperidones on the basis of the transamination of 1-substituted 2-methyl-4-piperidone methiodides by optically active -phenylethylamine was demonstrated; the optical yield of the asymmetric transamination is 50%. The occurrence of asymmetric synthesis was confirmed by the isolation of enantiomers of 2-methyl-4-piperidol by reduction of the individual diastereomers of 1--phenyl-ethyl-2-methyl-4-piperidone to the corresponding 4-piperidols with subsequent removal of the chiral substituent attached to the nitrogen atom.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1378–1382, October, 1985.     

Synthesis of new <Emphasis Type="Italic">N</Emphasis>-(pyridin-3-ylmethyl)-2-aminothiazoline derivatives possessing anticholinesterase and antiradical activity as potential multifunctional agents for the treatment of neurodegenerative diseases

New N-(pyridin-3-ylmethyl)-2-aminothiazolines containing various substituents at the 5 position of the thiazoline ring and the 4-tert-butylbenzyl, 4-isopropylbenzyl, or 4-fluorobenzyl moiety at the nitrogen atom of the amino group were synthesized. The inhibitory activity of the synthesized compounds against human erythrocyte acetylcholinesterase (AChE, EC 3.1.1.7), equine serum butyrylcholinesterase (BChE, EC 3.1.1.8), and porcine liver carboxylesterase (CaE, EC 3.1.1.1) was evaluated and their antioxidant properties were studied by ABTS assay. N-(Pyridin-3-ylmethyl)-2-aminothiazolines proveded to be very weak AChE inhibitors, while their inhibitory activity against BChE and CaE was structure-dependent. 2-Aminothiazolines containing the 4-tert-butylbenzyl moiety are more efficient BChE inhibitors compared to the derivatives containing the 4-isopropylbenzyl or 4-fluorobenzyl substituent. An analysis of the dependence of the esterase profile of N-(pyridin-3-ylmethyl)-2-aminothiazolines on the structure of the substituent at the 5 position of the thiazoline ring of these compounds demonstrated that the derivatives containing the iodomethyl substituent possess the highest anti-BChE activity, the compounds with R² = H and R³ = CH₂I have the optimal esterase profile. Regardless of the structure of the substituents in the benzyl moiety, all N-(pyridin-3-ylmethyl)-2-aminothiazolines containing the iodomethyl substituent at the 5 position of the thiazoline ring exhibited high radical scavenging activity comparable with that of the standard antioxidant Trolox. N-(Pyridin-3-ylmethyl)-2-aminothiazolines were shown to be a new promising class of compounds for the design of multifunctional agents for the treatment of neurodegenerative diseases.     

Low-temperature X-ray study of benzoid-quinoid tautomerism in crystals of 2-(N,N-diphenylhydrazinoethylidene)-3(2H)-benzo[b]thiophenone

An X-ray investigation of 2-(N,N-diphenylhydrazinoethylidene)-3(2H)-benzo[b]thiophenone was performed at room and low (–80 °C) temperatures. It was established that the structure of this compound in the crystalline state at R-20 °C is intermediate between the ketoenehydrazine and hydroxyhydrazone forms, while at –80 °C the molecular structure is completely transformed to the hydroxyhydrazone form. This confirms the dynamic nature of hydrogen atom disordering in the molecule at 20 °C.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 104–106, January, 1995.This work was financially supported by the Russian Foundation for Basic Research (Project No. 93-03-04355).     

Photochemical properties and the structure of 6-methyl-2,4-diphenyl-1-(p-tolyl)pyrimidinium perchlorate and the product of its photocyclization

The structure and photochemical properties of 6-methyl-2,4-diphenyl-1-(p-tolyl)pyrimidinium perchlorate (1) and 4,8-dimethyl-2-phenylpyrimido[1,2-f]phenanthridinium (2) formed as a result of photocyclization of1 have been studied. The crystal structure of compound1 has been studied at –140 °C and 25 °C. In cation1, theN-tolyl substituent and -Ph ring are noncoplanar with the pyrimidinium fragment (the angles are 67.9° and 41.1°, respectively), while the angle between the -Ph ring and the pyrimidinium moiety is only 7.1° (–140 °C). The photocyclization product2 has a flattened structure.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1731–1735, September, 1995.This work was partly (studies performed at Scientific Research Institute of Physical and Organic Chemistry at Rostov State University) supported by the Science Foundation Russian Universities.     

New strategies for the synthesis of N-alkylated indoles (Review)

New data, mostly published in the last five years, on methods for the synthesis of N-alkylated indoles both as a result of direct introduction of the alkyl substituent at the nitrogen atom and by construction of the indole heterocyclic system are reviewed. Only examples of indole derivatives containing branched, sterically hindered, and chiral alkyl substituents at the nitrogen atom are discussed.     

Mass spectra of substituted 4-aminopiperidines with a shielded nitrogen atom

The principal fragmentation pathway of 4-aminopiperidines under the influence of electron impact are determined by charge localization on the nitrogen atom of the piperidine ring or on the nitrogen atom of the substituent in the 4 position. In the case of electron-donor substituents in the 4 position and in the absence of a substituent attached to the nitrogen atom of the polysubstituted piperidine ring the charge is primarily localized on the nitrogen atom of the substituent; this is expressed in the specific fragmentation pathways. The principles found in this research make it possible to establish the structures of nitrogen-containing compounds that are similar to the investigated compounds.Communication 10 in the series Application of mass spectrometry in structural and stereochemical studies. See [1] for Communication 9.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 72–77, January, 1981.     

Structure of 1,1,3,3-bis(trimethylene)-1,3-di-α-naphthyldisiloxane

Conclusions 1,1,3,3-Bis(trimethylene)-1,3-di--naphthyldisiloxane is a centrosymmetric dimer with a linear SiOSi group. The silacyclobutane fragment has a folded conformation with flexure angle =28.9°. The transannular Si...C distance is 2.350(3) Å. The presence of an electronegative substituent (oxygen atom) at the silicon atom leads to a contraction of the Si-C bonds in the heterocycle to 1.863(2) Å.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1030–1034, May, 1985.     

Synthesis of N-alkylanthranilamides with a chiral substituent at the nitrogen atom

Novel anthranilamides containing a chiral substituent at the nitrogen atom and different substituents on the benzene ring were prepared from the corresponding isatins in good yields and high enantioselectivities (up to 98%).     

Features of signals from protons of alkyl group on boron atom in PMR spectra of 1,3,2-oxazaborinanes

It has been shown that the signal from isopropyl-group protons in the PMR spectra of 2-isopropyl-1,3,2-oxazaborinanes degenerates into a singlet; but the protons of the gem-dimethyl groups and the methylene link in an isobutyl substituent on the boron atom, where a chiral center is present in the molecule, may manifest anisochronicity. In the latter case, is determined by the character of the solvent, the temperature, and the contribution of the conformation with a flexible form.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1262–1264, September, 1991.     

Peculiarities of electroreduction of trans-2-allyl-6-methyl(allyl,phenyl)-1,2,3,6-tetrahydropyridines

Electrochemical reduction of trans-2-allyl-6-R-1,2,3,6-tetrahydropyridines (R = Me, All, and Ph) on the mercury cathode in anhydrous DMF (with 0.1 M Bu₄NClO₄ as the supporting electrolyte) resulted in catalytic hydrogen evolution, while in the case of anhydrous DMF the electrochemical activity of the endocyclic double bond was dictated by the nature of the R substituent at the carbon atom neighboring the double bond. The electrocatalytic hydrogenation of the piperideines under study on the Ni (Ni_disp/Ni) cathode in 40% aqueous DMF in the presence of a tenfold excess of AcOH yielded the corresponding trans-2-propyl-6-R¹-piperidines (R¹ = Me, Pr, and Ph). Using trans-2,6-diallyl-1,2,3,6-tetrahydropyridine as an example, the conditions (with annealed copper as the cathode) for selective hydrogenation of the double bonds in allyl substituents with preservation of the endocyclic double bond were found.     

Stereochemistry of the asymmetric reduction of N-(α-phenylethyl)-δ8,9-hexahydro-4-pyrindone

The reduction of optically active N-(-phenylethyl)-^8,9-hexahydro-4-pyrindone with lithium aluminum hydride proceeds as asymmetric stereospecific 1,4-hydride addition an leads to the formation of primarily the thermodynamically stable trans-(8S,9S)-N-(-phenylethyl) octahydro-4-pyrindone and a small amount of the corresponding cis isomer. Only cis-(8S,9S)-octahydro-4-pyrindone was obtained from each isomer and the mixture of isomers after removal of the chiral substituent from the nitrogen atom. The absolute configurations of the compounds obtained were established on the basis of circular dichroism data and the octant rule.Communication XLVIII from Stereochemical Studies. See [1] for communication XLVII.Translated from Khimiya Getero-tsiklicheskikh Soedinenii, No. 2, pp. 240–245, February, 1978.     

HPLC Enantioseparation of 1-(α-Aminobenzyl)-2-naphthol and 2-(α-Aminobenzyl)-1-naphthol Analogs on a β-Cyclodextrin-Based Chiral Stationary Phase

The enantiomers of 1-(α-aminobenzyl)-2-naphthol and 2-(α-aminobenzyl)-1-naphthol analogs were separated isothermally on a 3,5-dimethylphenylcarbamoylated β-cyclodextrin-based chiral stationary phase (Cyclobond DMP), with an n-hexane/alcohol modifier as mobile phase. Optimization of the separation was achieved by variation of combinations of the polar mobile phase additives ethanol and methanol. The nature and position of the α-aminobenzyl substituent of the 1- and 2-naphthol analogs influenced the retention and the selectivity.     

Direct C-nitration of cyclic α,β-unsaturated oximes under the action of sodium nitrite and acetic acid in methanol

Using a number of cyclic ,-unsaturated oximes of the terpene series and some simplest model compounds as examples, unsaturated oximes bearing a hydrogen atom at the -carbon atom were demonstrated to be converted into -hydroxyiminonitroalkenes under the action of sodium nitrite and acetic acid in methanol. In the case of the introduction of an alkyl substituent at the terminal carbon atom of the diene C=C—C=NOH fragment, the reaction performed under the same conditions gave rise exclusively to conjugated ketone (a deoximation product).     

Synthesis and Comparative Analysis of the Steric and Supramolecular Structures of Diastereomers of 4,4-Bis(trifluoromethyl)-2-(fluoroalkoxy)-6,7-benzo-1,3,2λ5- dioxaphosphepin-5-one 2-Oxides

Reaction with hexafluoroacetone of 2-fluoroalkoxy-5,6-benzo-1,3,2-dioxophosphorinan-5-ones containing a chiral fluorinated exocyclic substituent on the phosphorus atom, with hexafluoroacetone leads to formation of 4,4-bis(trifluoromethyl)-6,7-benzo-1,4,2-dioxaphosphepines with a high regio- and stereoselectivity. The configuration of all isolated individual diastereomers was established by X-ray diffraction. The molecular and supramolecular structure of the compounds were examined in terms of the proposed model that takes account of the revealed effect of separation of hydrophilic and lipophilic regions in the crystal.     

Mechanism of the fragmentation of the methyl ester of α-bromo-α-(3-bromoadamantyl-1) acetic acid

The mechanism and stereochemical peculiarities of the fragmentation of -dibromo-derivatives of adamantane by zinc in DMFA were investigated on the example of chiral dibromides. It was shown that the reaction proceeds with the formation of intermediate carbanions; moreover, the formation of a carbanion at the chiral center is accompanied by racemization, and at the bridge carbon atom by transformation of the central chirality of the initial dibromide into the planar chirality of derivatives of 3,7-dimethylenebicyclo[3. 3.1]nonane. This transformation, which obeys definite stereoelectronic requirements, provides for the genetic interrelationship of the configurations of the fragmentable dibromides and fragmentation products.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 5, pp. 620–623, September–October, 1985.     

The Effect of cis-trans Isomerism on the Electronic-vibrational Structure of the Ground and Excited States and Reactivity of 2-(2-Furyl)- and 2-(2-Thienyl)oxazole

The fluorescent properties, structure, and electronic structure of the ground and excited singlet and triplet electronic states of the cis and trans forms of 4,5-dihydro-2-(2-furyl)oxazole, 4,4-dihydro-2-(2-thienyl)oxazole, 2-(2-furyl)oxazole (FO), and 2-(2-thienyl)oxazole (TO) have been studied. The orbital nature of the lower excited singlet and triplet states has been studied by the semiempirical INDO/S (valence approximation) and PPP/S ( approximation) methods. It was shown that for FO and TO molecules the lower triplet state is of the * type, for which delocalization of the electronic excitation on atoms is characteristic. In the singlet excitation state inversion was observed of the energy levels of the delocalized * states and n* states localized over several bonds (for the free TO and FO molecules the lower excited singlet states S₁* were assigned to * and n* types respectively). Owing to the low position of the T * and T _n* levels relative to the singlet level of * type, the rate constant for intercombination conversion is greater than the rate constant for radiative decay. Consequently an efficient population of the triplet states of the molecules occurs under conditions of electronic-vibrational excitation. The direction of reactions during synthesis was compared with the localization indices in the ground state for electrophilic, nucleophilic, and radical substitution, and also with the excitation localization numbers L for a wide selection of electronically excited states. It was concluded that the change in the structure of the azole molecule on replacing an O atom by an S atom, or on changing from a partially hydrogenated to a heteroaromatic system, was the main reason for the change of all the spectral parameters characterizing the electronic-vibrational or the spin-orbital interaction of the most reactive groups of atoms in the molecular structure.     

Photochromic properties of some N-substituted 3,3-dimethyl-6′-nitroindoline-2-spiro-2′-2H-chromenes

A number of photochromic 1-carbethoxymethyl-3,3-dimethyl-6-nitroindoline-2-spiro-2-2H-chromenes were synthesized. The introduction of a carbethoxymethyl substituent at the nitrogen atom instead of a methyl group somewhat increases the rate of dark decolorization of the photomerocyanines without appreciably affecting the spectral characteristics. The results are compared with the analogous spectral-kinetic characteristics of 1-phenyl-substituted compounds.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1640–1644, December, 1977.     

Organoboron compounds

Conclusions ³J_HH SSCC values and the¹³C chemical shifts of derivatives of 3-borabicyclo[3.3.1]nonane with a three-coordinated boron atom have a flattened double-chair conformation. The derivatives with a four-coordinated boron atom and a substituent at the 7 position have predominantly the chair-boat conformation, and the cyclohexane ring has the boat form; the the exceptions are the compounds with an internal donor-acceptor bond between boron and the 7 substituent.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 341–352, February, 1981.