Photochemical rearrangement of diarylethenes: synthesis of functionalized phenanthrenes.

A novel protocol for the synthesis of functionalized phenanthrenes through photocyclization of diarylethenes (DAE) under UV irradiation is proposed. The reaction proceeds through 6π-electrocyclization with the formation of a cyclic (closed) intermediate that undergoes a rearrangement affording unsymmetrical phenanthrenes in good yields. However, in contrast to benzene derivatives, the photocyclization of naphthalene diarylethenes proceeds more slowly, which is confirmed by DFT calculations. The transformation was performed on a 1 mmol scale. The scalability showed that the diarylethenes bearing oxazole, thiazole, pyrazole and imidazole as aryl moieties are more prone to photorearrangement and can be used in preparative organic synthesis.

Golden rule kinetics of transfer reactions in condensed phase: the microscopic model of electron transfer reactions in disordered solid matrices.

The algorithm for a theoretical calculation of transfer reaction rates for light quantum particles (i.e., the electron and H-atom transfers) in non-polar solid matrices is formulated and justified. The mechanism postulated involves a local mode (an either intra- or inter-molecular one) serving as a mediator which accomplishes the energy exchange between the reacting high-frequency quantum mode and the phonon modes belonging to the environment. This approach uses as a background the Fermi golden rule beyond the usually applied spin-boson approximation. The dynamical treatment rests on the one-dimensional version of the standard quantum relaxation equation for the reduced density matrix, which describes the frequency fluctuation spectrum for the local mode under consideration. The temperature dependence of a reaction rate is controlled by the dimensionless parameter ξ0 = ℏω0/k(B)T where ω0 is the frequency of the local mode and T is the temperature. The realization of the computational scheme is different for the high/intermediate (ξ0 < 1 - 3) and for low (ξ0 ≫ 1) temperature ranges. For the first (quasi-classical) kinetic regime, the Redfield approximation to the solution of the relaxation equation proved to be sufficient and efficient in practical applications. The study of the essentially quantum-mechanical low-temperature kinetic regime in its asymptotic limit requires the implementation of the exact relaxation equation. The coherent mechanism providing a non-vanishing reaction rate has been revealed when T → 0. An accurate computational methodology for the cross-over kinetic regime needs a further elaboration. The original model of the hopping mechanism for electronic conduction in photosensitive organic materials is considered, based on the above techniques. The electron transfer (ET) in active centers of such systems proceeds via local intra- and intermolecular modes. The active modes, as a rule, operate beyond the kinetic regimes, which are usually postulated in the existing theories of the ET. Our alternative dynamic ET model for local modes immersed in the continuum harmonic medium is formulated for both classical and quantum regimes, and accounts explicitly for the mode∕medium interaction. The kinetics of the energy exchange between the local ET subsystem and the surrounding environment essentially determine the total ET rate. The efficient computer code for rate computations is elaborated on. The computations are available for a wide range of system parameters, such as the temperature, external field, local mode frequency, and characteristics of mode/medium interaction. The relation of the present approach to the Marcus ET theory and to the quantum-statistical reaction rate theory [V. G. Levich and R. R. Dogonadze, Dokl. Akad. Nauk SSSR, Ser. Fiz. Khim. 124, 213 (1959); J. Ulstrup, Charge Transfer in Condensed Media (Springer, Berlin, 1979); M. Bixon and J. Jortner, Adv. Chem. Phys. 106, 35 (1999)] underlying it is discussed and illustrated by the results of computations for practically important target systems.

[Peculiarities of stress erosive ulcerous injuries of stomach and small intestine].

AIM: The aim of this investigation is to estimate the role of systemic injuries of lipid metabolism in pathogenesis of ulceration on the model of stress ulcerogenesis. MATERIALS AND METHODS: There have been assumed as a basis of the work experimental investigations on 60 pubertal white rats of both sexes weighing 200 gr. There was studied the state of macroscopic picture of stomach and small intestine, qualitative and quantitative lipid composition, lipid peroxidation, phospholipase A2, catalase, superoxide dismutase in stomach tissues, small intestine and blood plasma. RESULTS: The facts of the experimental investigations show, that by the effect of ulceration stress there are processes, that underlie modifications of lipid components of cell structures' biomembranes, and registered by qualitative and quantitative changes of lipid composition. Intensification of lipid peroxidation and activation of phospholipase A2 are the key mechanisms of qualitative and quantitative composition of biomembranes' lipid components, and they reduce to beginnings of cascade of pathomorphological and pathophysiological reactions in cell structures, which cause beginnings of membrane destructive processes, that is as a basis of ulcerogenesis. CONCLUSION: In the result there is broken morphofunctional state of mucous membrane (one of the main factors of protection), that in the end makes it accessible substratum for other aggressive factors and promotes the formation of ulcerous defects.