A number of fused 4-oxo-1,3-diazabicyclo[4.1.0]heptane-6-carboxylates, a new type of compound, have been obtained by Diels -Alder cycloaddition between nucleophilic 2-azadienes and an electrophilic 2H-azirine. The reactions are completely endo-and regioselective, the azirine being added by its less hindered face to the diene. There are two isomers 7 and 8 formed from dienes 1 due either to isomerization of the cycloadducts 7 and 8 or by isomerization of the CvN bond of the diene during the reaction. The isomer 10 is formed from diene 2e, and a single diastereoisomer structure 4a -i is formed from dienes 11. Some pyrimidones 8a, 7c/8c, 7e, 10, 11d have been hydrolyzed leading to functionalised aziridines 12, 13 and 15. q
This work presents results of tensile testing of H400 stainless steel, DP600 and TRIP600
at different strain rates. Mechanical properties were determined from tensile test using flat sheet
specimens and recurring to different test techniques: servo-hydraulic machine and a tensile-loading
Hopkinson bar. The test results were used to compare different mechanical properties of the tested
steels and to validate constitutive equations intended to provide a mathematical description of strain
rate dependence, namely the Cowper-Symonds equation. Following previous research work in
dynamic material proprieties of multiphase and stainless steel grades, the energy absorption in
quasi-static crushing of thin walled section made of the tested materials was subsequently
investigated. Crush tests were performed in top-hat and hexagonal section tubes manufactured using
laser welding. The experimental results were compared in order to assess the efficiency of the
different steel grades for energy absorption.
Pyrimidine derivatives
Pyrimidine derivatives R 0510Cycloaddition of Methyl 2-(2,6-Dichlorophenyl)-2H-azirine-3-carboxylate to Electron-Rich 2-Azadienes. -The reaction of activated azadienes (I) with an electron-deficient 2H-azirine (II) is reported for the first time. Hydrolysis of the resulting tetrahydropyrimidinones [cf. (IIIa)] provides functionalized aziridine esters (V). -(ALVES*, M. J.; DURAES, M. M.; FORTES, A. G.; Tetrahedron Lett. 44 (2003) 27, 5079-5082; Dep. Quim., Univ. Minho, P-4710 Braga, Port.; Eng.) -Mais 40-159
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