Larin E.A.,Asinex Corporation |
Kochubei V.S.,Asinex Corporation |
Atroshchenko Y.M.,Tula State Pedagogical University
Beilstein Journal of Organic Chemistry | Year: 2014
The optimal conditions for regio- and stereoselective epoxide ring opening of N,N -disubstituted 1,2-epoxy-3-aminocyclopentanes by different nucleophilic reagents have been developed. The substituents on the nitrogen atom in the epoxide precursor and the orientation of the oxirane ring are crucial for the reaction outcome. Thus, treatment of (1RS,2SR,3SR)-1,2-epoxy-3-(N,N -dibenzylamino) cyclopentane ( 3b ) with amines gave a mixture of C1 and C2 regioadducts, while the use of (1RS,2SR,3SR)-1,2-epoxy-3-(N-benzyl-N -methylamino)cyclopentane ( 3a ) led ultimately to C1 adducts. Base-catalyzed aminolysis of epoxides 6a,b afforded mainly C1 adducts 13a,b arising from trans -diaxal opening of the epoxide ring. Using a Lewis acid catalyst, epoxides 6a,b were transformed into diaminocyclopentanols 14a,b via an alternative pathway involving the formation of aziridinium intermediate 17. © 2014 Larin et al; licensee Beilstein-Institut. License and terms: see end of document.
Novenko E.Y.,Russian Academy of Sciences |
Volkova E.M.,Tula State Pedagogical University |
Glasko M.P.,Russian Academy of Sciences |
Zuganova I.S.,Russian Academy of Sciences
Vegetation History and Archaeobotany | Year: 2012
New pollen and plant macrofossil data, backed by radiocarbon dates, from the Kulikovo battlefield area in the forest-steppe region of the Upper Don River basin (central part of European Russia) indicate that the area was covered by mosaic vegetation in the second half of the Holocene. Steppe communities dominated during the mid-late Atlantic (7.2-5.7 cal. kyr b. p.) and early Subatlantic (2.7-2.4 cal. kyr b. p.), while forest-steppe dominated during the Subboreal (2.7-5.7 cal. kyr b. p.), middle and late Subatlantic (2.4 cal. kyr b. p. - present). Climatic reconstructions based on these data show that landscape dynamics in the region were most probably driven by changes in effective moisture: an excess of precipitation over evaporation. Even small reductions in annual precipitation, accompanied by a rise in summer temperatures by 1-3°C above present values, were sufficient to increase the proportion of steppe communities within this landscape complex, and also probably resulted in higher frequencies of wildfires. Signals of anthropogenic disturbance of vegetation are clearly pronounced in the pollen and plant macrofossil records since the middle Atlantic. However, human-induced changes in the vegetation remain subtle until the medieval period. © 2011 Springer-Verlag.
Tsirulnikov S.,Tula State Pedagogical University |
Kysil V.,ChemDiv Inc. |
Ivachtchenko A.,ChemDiv Inc. |
Krasavin M.,Chemical Diversity Research Institute
Synthetic Communications | Year: 2010
2-Amino[1,3]benzothiazoles can be efficiently used as substrates for the Groebke-Blackburn (GB) reaction using equimolar trimethylsilyl chloride (TMSCl) as a promoter. This finding extends the utility of TMSCl in isocyanide-based multicomponent reactions (MCRs) and expands the scope of reactive 2-aminoazole participants for the GBMCR. © 2009 Taylor & Francis Group, LLC.
Khoroon L.V.,Tula State Pedagogical University
Russian Journal of Biological Invasions | Year: 2014
The paper describes a complex of random factors that precondition the first stages of secondary range formation and promote the appearance and the start of self-reproduction of populations of alien plant species and their mutual contacts. © 2014 Pleiades Publishing, Ltd.
Butuzov V.F.,Moscow State University |
Denisov I.V.,Tula State Pedagogical University
Automatic Control and Computer Sciences | Year: 2014
In a rectangular domain, the first boundary-value problem is considered for the following singularly perturbed elliptic equation: (Formula presented.) with the function F, which is nonlinear in u. The complete asymptotic solution expansion, which is uniform in a closed rectangle, is constructed for α > 1. If 0 < α < 1, the uniform asymptotic approximation is constructed as a zero and first approximation. The features of the asymptotic behavior are noted at α = 1. © 2014, Allerton Press, Inc.