The main object of research of our research group in the chemistry of heterocycles is isoindoles and their derivatives. Isoindoles - interesting and relatively not enough studied heterocycles. Their methods of synthesis and properties depend on many factors. Isoindoles, simple and condensed, very attractive to study new effects in the study of reactivity in cycloaddition reactions, Michael reactions, new rearrangements of tricyclic 7-azabenzonorbornene that formed from isoindoles and maleimide derivatives. For some isoindoles it is interesting to play on their tautomeric transformations, including those that include prototropy different from the known classical isoindole-isoindoline tautomerism. The most unusual is the synthesis and properties of cyanine dyes on the basis of condensed azoloisoindoles. Difficulty in interpreting a number of results will require the agglomeration of spectral properties. (UV, IR, NMR, 2D-spectra and X-ray structural analysis).
Three types of rearrangements at [4+2]-cycloaddition reactions of condensed isoindoles.
The study of isoindole derivatives and their chemical properties is an important area of heterocyclic chemistry with a long history of research. As a matter of fact the most typical reaction of [4+2]-cycloaddition was extensively studied for the simple isoindole which led to the discovery of criteria for the identification of exo- and endo-adducts. During the pioneering research the hypothesis of isoindole electronic structure was formulated and the possibility of the practical use of isoindole derivatives was discussed in numerous our works. Reaction of [4+2]-cycloaddition has been methodically studied in our scientific group over the past few decades. Among other results, we discovered three new rearrangements, each being a unique method of synthesis of the rearranged Michael-Diels-Alder adducts (intermediate 7-aza-benzonorbornene) of the first, second and third type of condensed isoindoles. The direction of the rearrangement depends on the electron structure of the condensed isoindoles.
Mechanism of rearrangement at [4+2]-cycloaddition reactions of non-condensed isoindoles, that predominantly exists in isoindoline tautomeric form.
Based on the spectral studies of 1-aminoisoindole we have observed that in solution the isoindolenine tautomer predominates. In spite of this fact but, taking into account the Curtin–Hammett principle, we undertaken the first study of the Diels–Alder reaction for 1-aminoisoindole as a typical representative of simple isoindoles in isoindoline form. We have studied the interaction of 1-aminoisoindole with maleimide derivates and demonstrated that the products are rearranged 1:2 composition adducts. We have proposed a rearrangement mechanism, detected and identified the intermediate Diels–Alder products containing both endo- and exo adducts.
The presence of azido-tetrazole tautomerism in the series of tetrazolo[5,1-a]isoindoles has been suggested initially using quantum-chemical calculations [R.M. Claramunt, J. Elguero, A. Fruchier, M.J. Nye, Afinidad, 1977, 34, 350, 545–551.]. Later, the possibility of the existence of such tautomerism in tetrazoloisoindoles was considered and we have established the possibility of the tetrazole ring opening in acyl derivatives with the elimination of free nitrogen under certain conditions.
Cyanine dyes - the derivatives of tetrazoloisoindole and triazoloisoindole
Cyanine dyes have long been widespread practical use. Interest in this class of compounds has recently increased dramatically. This is due to the emergence of new non-traditional uses of cyanine dyes. New application possibilities require careful study of the electronic structure and the factors that can influence it. Cyanine dyes - the derivatives of tetrazoloisoindole and triazoloisoindole (R = Alk, Ar, Het), which we synthesized, had unusually high logarithms of extinction.