INVESTIGATION OF THE FORMATION REACTION OF σ-ADDUTS OF 2-R-5,7-DINITROBENZOXAZOLES

Abstract

Background. The problem of the synthesis of new effective biologically active compounds remains an urgent task of modern chemical science. It is known that oxazole derivatives have a broad spectrum of physiological activity. In this regard, expanding the range of these derivatives seems to be an urgent task. One of the promising methods for the functionalization of nitro derivatives of heterocycles is reductive activation, which proceeds through the formation of relatively labile, highly reactive hydride σ-adducts, which can then be used to synthesize new biologically active compounds. This work is devoted to the study of the formation reaction of anionic σ-complexes of 2-R-5,7-dinitrobenzoxazoles under the action of sodium tetrahydroborate.
 Purpose. To study the reaction of formation of anionic σ-complexes of 2-R-5,7-dinitrobenzoxazoles by spectral methods.
 Materials and methods. The reaction mechanism for the formation of anionic σ-adducts 2-R-5,7-dinitrobenzoxazoles under the action of sodium tetrahydroborate was proposed on the basis of the data of UV spectra obtained by carrying out the studied reaction in the cuvette of an SF 103 spectrophotometer. The structure of the obtained compounds was also proved using 1H-, 13C - and 2D-correlation NMR spectroscopy.
 Results. Double-charged hydride σ-adducts based on 2-R-5,7-dinitrobenzoxazoles were synthesized under the action of sodium tetrahydroborate. The structure of the formed adducts was proved by the methods of electronic and NMR spectroscopy, and a probable mechanism of the reaction was proposed.
 Conclusion. The reaction of mild reduction of dinitro derivatives of benzo[d]oxazole under the action of sodium tetrahydroborate was studied. As a result, the corresponding hydride σ-complexes, which are sodium salts of bis-nitroic acids of benzo[d]oxazole, were isolated and identified by spectral methods. The mechanism of the reaction of their formation has been suggested.