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Aroyl(quinoxalinyl)ketenes generated by thermolysis of 5-aryl-4-(3-arylquinoxalin-2-yl)-2,3-di-hydrofuran-2,3-diones act as dienes in [4 + 2]-cycloaddition at the carbonyl group of aldehydes and ketones to afford 2-substituted 6-aryl-5-(3-arylquinoxalin-2-yl)-4H-1,3-dioxin-4-ones. The structure of 5-(3-p-tolylquino-xalin-2-yl)-4H-1,3-dioxine-2-spiro-2'-adamantan-4-one was proved by X-ray analysis.  相似文献   
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Complexes formed by interaction of E(C6F5)3 (E = B, Al, Ga, In) with excess of acetonitrile (AN) were structurally characterized. Quantum chemical computations indicate that for Al(C6F5)3 and In(C6F5)3 the formation of a complex of 1:2 composition is more advantageous than for B(C6F5)3 and Ga(C6F5)3, in line with experimental observations. Formation of the solvate [Al(C6F5)3 · 2AN] · AN is in agreement with predicted thermodynamic instability of [Al(C6F5)3 · 3AN]. Tensimetry study of B(C6F5)3 · CH3CN reveals its stability in the solid state up to 197 °C. With the temperature increase, the complex undergoes irreversible thermal decomposition with pentafluorobenzene formation.  相似文献   
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In the paper presented, we continue the research in the elastic properties of seven-constant tetragonal crystals and nano/microtubes. Our previous study concerned tension of this type of structures, and here we are dealing with their torsion, Poynting’s effect or axial extension under torsion with no tensile force, and torsional stiffness. It is demonstrated that there exists inverse Poynting’s effect: the tubes experience torsion under tension without applying a torque.  相似文献   
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Donor-acceptor complexes of borazine (BZ) and its substituted derivatives with Lewis acids (A = MCl(3), MBr(3); M = B, Al, Ga) and Lewis bases (D = NH(3), Py) have been theoretically studied at the B3LYP/TZVP level of theory. The calculations showed that complexes with Lewis bases only are unstable with respect to dissociation into their components, while complexes with Lewis acids only (such as aluminum and gallium trihalides) are stable. It was shown that formation of ternary D→BZ→A complexes may be achieved by subsequent introduction of the Lewis acid (acceptor A) and the Lewis base (donor D) to borazine. The nature of substituents in the borazine ring, their number, and position were shown to have only minor influence on the stability of ternary D→BZ→A complexes due to the compensation effect. Much weaker acceptor properties of borazine are explained in terms of large endothermic pyramidalization energy of the boron center in the borazine ring. In contrast to borazine, binary complexes of the isoelectronic benzene were predicted to be weakly bound even in the case of very strong Lewis acids; ternary DA complexes of benzene were predicted to be unbound. The donor-acceptor complex formation was predicted to significantly reduce both the endothermicity (by 70-95 kJ mol(-1)) and the activation energy (by 40-70 kJ mol(-1)) for the borazine hydrogenation. Thus, activation of the borazine ring by Lewis acids may be a facile way for the hydrogenation of borazines and polyborazines.  相似文献   
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Conclusions A series of carbocyclohexyloxyamino acids were subjected to hydrobrominolysis. The side groups of the amino acids affect the cleavage rate of the CCO group during hydrobrominolysis, which is probably determined by the total influence of the induction and steric effects of these groups.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 924–926, May, 1966.  相似文献   
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