Cyclomagnesiation of nitrogen-containing 1,2-dienes with grignard compounds catalyzed by Cp<Subscript>2</Subscript>TiCl<Subscript>2</Subscript>

Cyclomagnesiation of nitrogen-containing 1,2-dienes with Grignard compounds in the presence of activated magnesium and Cp₂TiCl₂ as catalyst afforded 2,5-bis(aminoalkylidene)magnesacyclopentanes in high yield.     

Diastereotopic splitting in the 13C NMR spectra of sulfur homofullerenes and methanofullerenes with chiral fragments

Using gauge‐invariant atomic orbital PBE/3ζ quantum chemistry approach, ¹³C NMR chemical shifts and diastereotopic splittings of sp² fullerenyl carbons of a number of sulfur homofullerenes and methanofullerenes have been predicted and discussed. An anisochrony of fullerene carbons is caused by a chiral center of attached moieties. Clearly distinguishable diastereotopic pairs (from 8 to 11) of fullerenyl carbons of homofullerenes were observed. Unambiguous assignments of ¹³C NMR chemical shifts were performed, and diastereotopic splittings of methanofullerenes were observed for α, β and γ to a functionalization site. Copyright © 2013 John Wiley & Sons, Ltd.     

7α-alkylation, 7,7-bisalkylation,and reduction of the 20-oxo group of poststerone in reactions with alkyl halides in lithium–ammonia solution

Reactions of poststerone with methyl iodide, allyl bromide, and propargyl bromide in lithium–ammonia solution resulted in its completely stereoselective 7α-alkylation accompanied by reduction of the 20-oxo group with formation of equimolar amounts of 20R- and 20S-hydroxy derivatives. The reaction of poststerone with excess allyl bromide afforded 7,7-bis-allyl 20R- and 20S-alcohols at a ratio of 3: 1. The reduction of the 20-oxo group in the alkylation of poststerone with excess propargyl bromide led to the formation of an equimolar mixture of Δ⁸⁽¹⁴⁾- and Δ⁸⁽⁹⁾-isomers with exclusive S configuration of C²⁰.     

Turbulent convective heat transfer in an inclined tube filled with sodium

Turbulent free convection of liquid sodium in a straight thermally insulated tube with a length equal to 20 diameters and with end heat exchangers ensuring a fixed temperature drop is investigated experimentally. The experiments are performed for a fixed Rayleigh number Ra = 2.4 × 10⁶ and various angles of inclination of the tube relative to the vertical. A strong dependence of the power transferred along the tube on the angle of inclination is revealed: the Nusselt number in the angular range under investigation changes by an order of magnitude with a maximum at the angle of 65° with the vertical. The characteristics of large-scale circulation and turbulent temperature pulsations show that convective heat transfer is mainly determined by the velocity of large-scale circulation of sodium. Turbulent pulsations are maximal for small angles of inclination (α = 20°–30°) and reduce the heat flux along the channel, although in the limit of small angles (vertical tube), there is no large-scale circulation, and the convective heat flux, which is an order of magnitude larger than the molecular heat flux, is ensured only by small scale (turbulent) flow.     

Identification and Biological Activity of Volatile Organic Compounds Emitted by Plants and Insects. IV. Composition of Vapor Isolated from Certain Species of Artemisia Plants

The components of fragrance from four wormwood species of theArtemisiaL. genus were analyzed by GC-MS. The major and minor components of volatile essential oils typical of the studied plant species were determined.     

Structural and dynamic microheterogeneity of rubber powder

Spin probe EPR spectroscopy was used to study the local dynamics of vulcanizates of an ethylenepropylene-diene elastomer and rubber powders prepared from them. It was revealed that the preparation of rubber powders is accompanied by the formation of a polymer network with an essentially nonuniform local structure.     

Identification and biological activity of the volatile organic substances emitted by plants and insects II. Sesquiterpene composition of the native scent of leaves of the potatoSolanum tuberosum

By dynamic gas extraction of the volatile components of the native scent of the leaves of the potatoSolanum tuberosum L. growing under natural conditions, followed by the gas-chromatographic separation and massspectrometric analysis of the substances obtained, the following sesquiterpene compounds have been identified:trans-andcis-caryophyllenes, -ylangene, -copaene, -bourbonene, -elemene, Z--farnesene, aromadendrene, -humulene, -elemene, -bisabolene, -cadinene, and -cadinene.Institute of Petrochemistry and Catalysis, Academy of Sciences of the Republic of Bashkortostan, and Ufa Scientific Center, Russian Academy of Sciences. Ufa-450075, Prospekt Oktyabrya, 141, tel./fax 7+(3472) 312750; ink@anrb.ru. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 472–477, July–August, 1999.     

Induced radiation by charged particles moving in a plane electromagnetic wave

It is shown that when a charged particle moving in the field of a plane electromagnetic wave is subjected to another electromagnetic wave, incident at some angle with respect to the first, induced radiation and absorption occur. Under certain conditions the induced radiation predominates over the absorption.Translated from Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 50–53, September, 1969.The authors thank professor I. M. Ternov for useful discussions.