Approach to preparative synthesis of <Emphasis Type="Italic">ortho</Emphasis>-(1-methylbut-2-en-1-yl)anilines,precursors of new cytotoxic heterocycles

The reaction of aromatic Claisen rearrangement of N-(1-methylbut-2-en-1-yl)anilines in the presence of p-toluenesulfonic acid was investigated. N-Tosyl-2-(1-iodoethyl)-3-methylindoline derivatives were obtained; one of them exhibited a cytotoxic activity.     

Fabrication of nanostructured silicon surface using selective chemical etching

A two-stage process based on selective chemical etching induced by metal nanoclusters is used to fabricate nanostructured surfaces of silicon plates with a relatively low reflectance. At silicon surfaces covered with silver nanoclusters, the SERS effect is observed for rhodamine concentrations of about 10^–12 M. At certain technological parameters, the depth of the nanostructured layer weakly depends on the conditions for the two-stage etching, in particular, etching time. Under otherwise equal conditions for etching, the rate of the formation of textured layer in the p-type silicon is two times greater than the formation rate in the n-type silicon.     

Enhanced generalised beam theory buckling formulation to handle transverse load application effects

This work deals with the development, finite element implementation and application of a generalised beam theory (GBT) formulation intended to analyse the localised, local, distortional and global buckling behaviour of thin-walled steel beams and frames subjected to transverse loads applied at various member cross-section points (away from its shear centre). In order to take into account the effects stemming from the transverse load position, the GBT buckling formulation must incorporate geometrical stiffness terms stemming from either (i) the internal work of the pre-buckling transversal normal stresses (“exact” formulation) or (ii) the external work of the applied transverse loads (approximate/simplified formulation). After presenting the main concepts and procedures involved in the development of the above “exact” and simplified formulations, the paper addresses the corresponding numerical implementations. Then, in order to illustrate their application and capabilities, as well as the limitations of the simplified formulation, various numerical result sets are presented and discussed. The accuracy of the GBT-based results is assessed through the comparison with “exact” values, yielded by rigorous shell finite element analyses carried out in the code Ansys.     

Flexible Electrode Made of Graphene and Few-Layer Graphite

A method of obtaining graphene oxide from Hummers-modified natural flake graphite with subsequent synthesis of reduced graphene and few-layer graphite has been suggested. The structure and electrical performance of the synthesized material have been studied. The feasibility of making a high-capacitance flexible electrode using polyethylene substrates covered by a conductive ink has been demonstrated.

     

Negative-ion mass spectra of diterpene alkaloids with the keto group in the 6- or 7-position

Processes resulting in the formation of negative ions by molecules of some diterpene alkaloids via resonance electron capture have been studied. The mass spectra of these compounds have a small number of lines represented largely by intense peaks in the thermal electron energy region and are due to electron capture onto the lower unoccupied molecular orbital, which is π*-C=O or π*-Ph-C=O in character.     

A revised mechanism of thermal decay of arylnitroso oxides

The electronic spectra were measured and the unimolecular decay kinetics of the isomeric forms (cis and trans) of 4-methoxyphenylnitroso oxide in acetonitrile, benzene, and hexane was studied using flash photolysis. The cis form absorbed in a shorter wavelength region and was more labile than the trans form. The difference between the reactivity of the two species increased on going from hexane to acetonitrile. The temperature dependences of reaction rate constants were studied for both isomeric forms. The analysis of products of flash photolysis of 4-methoxyphenyl azide in the presence of oxygen allowed for understanding the mechanism of thermal decay of nitroso oxides. It was shown that the trans nitroso oxide is converted into cis nitroso oxide. The latter undergoes an unusual ring cleavage reaction to form 4-methoxy-6-oxohexa-2,4-dienenitrile N-oxide derivative. We conclude that the nitro- and nitrosobenzenes, which are the main products of the steady-state photolysis of aromatic azides in the presence of oxygen, are formed by the photochemical transformation of the nitroso oxides.     

Magnetic birefringence effect in solutions of paramagnetic substances. 5. Structure of adducts of certain α-epoxides and keto derivatives with Dy(III) dipivaloylmethanate

Adduct formation of Dy(DPM)₃ and Eu(DPM)₃ with propylene oxide, 3-carene trans- and cis-oxides, cyclohexanone, d- and -camphor, --bromocamphor, and DMF has been studied using paramagnetic birefringence and polarimetry. The orientation of the chelate rings in Ln(DPM)₃ and the composition and structure of the adducts formed were determined.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1979–1985, September, 1991.     

Self-assembly of frame structures. 10. Stereochemistry of 2,5-dioxabicyclo [2.2.1]heptane-3,6-digne

By optimization of the geometry of 2, 5-dioxabicyclo[2. 2.1]heptane-3.6-dione (1) with an ab initio (RHF/6-31 G') calculation, we have found that a single synchro(+, +)-twist form (A) corresponds to the (1 R,4R)-enantiomer (the dihedral angles of the lactone bridges are ₀ = 2.6°). According to MM2(91) and MM3(92) calculations, (1R,4R)-1 exists as the s-ynchro(+, +)-A-twist ( ₀ = 3.9°) and the synchro(-, -)-B-twist ( = -3.8°) forms, respectively. Investigating the torsional energy surface of the dilactone 1 (MM2(91)), we found only the (1R,4R,P)-diastereomeric form (A), which is stabilized compared with the (1R,4P,M) form (B) (probably as a result of the more preferred dipole-dipole interaction of the carbonyl groups). According to the calculated puckering coordinates, the five-membered and six-membered moieties of the bicycle 1 are flattened compared with norbornane.Institute of Chemical Physics at Chernogolovka. Russian Academy of Sciences, Chernogolovka, Moscow Oblast 142432. Department of Chemistry, University of Calgary, Alberta, Canada T2N 1N4. Department of Chemistry, College of Sciences, Autonomous University of Barcelona, Bellaterra 08193, Spain. Laboratory of Organic Chemistry, College of Pharmacy, University of Barcelona, Barcelona 08028, Spain. N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow 117977. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1479-1488, November, 1995.     

Sulfur ylides. 12. Optically active keto stabilized sulfur ylide obtained from L-proline: synthesis and study

Optically active keto stabilized sulfur ylide was synthesized from L-proline. The reactions of the ylide with methyl acrylate and methyl vinyl ketone afforded 1,2-disubstituted cyclopropanes. In the case of acrylonitrile, a mixture of 1,2- and 1,1-disubstituted cyclopropanes was obtained. Acylation of the ylide with acetic anhydride gave twice stabilized sulfur ylide.