Chemoselectivity of Nitroxylation of Cage Hydrocarbons
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oselectivity of Nitroxylation of Cage Hydrocarbons Yu. N. Klimochkina, M. V. Leonovaa, and E. A. Ivlevaa,* a
Samara State Technical University, Samara, 443100 Russia *e-mail: [email protected]
Received June 15, 2020; revised June 27, 2020; accepted July 2, 2020
Abstract—The composition of reaction mixtures obtained by nitroxylation of 13 cage hydrocarbons with 100% nitric acid and its mixtures with acetic acid, acetic anhydride, and methylene chloride has been studied. More reactive substrates react with lowest selectivity regardless of the reaction medium. The primary nitroxylation products of cage hydrocarbons are nitrooxy derivatives. The compositions of reaction mixtures obtained in the reactions of some cage hydrocarbons with nitric anhydride in carbon tetrachloride have been determined. Keywords: chemoselectivity, nitroxylation, cage hydrocarbons, fuming nitric acid, nitric anhydride, nitrooxy derivatives
DOI: 10.1134/S107042802010005X Polyfunctional adamantane derivatives have found application as key building blocks for the design of materials possessing a combination of practically important properties. In particular, molecular electronic devices [1], flame-resistant polycarbonate materials [2], metal–organic coordination polymers [3–5], gas adsorbents [6], and catalysts [7, 8] have been developed. 1,3,5,7-Tetrasubstituted polyfunctional adamantanes are frequently used for these purposes [9]. On the other hand, the synthesis of polysubstituted adamantanes is complicated by difficulties in the search for readily accessible starting materials. There is a need of a chemical functionality vector that could make it possible to easily modify an initial molecule with a good yield. Such vector may be the presence of a nitrooxy (ONO2) group therein. Nitrooxy derivatives seem to be more appropriate substrates than halogen and hydroxy derivatives in the synthesis of polyfunctionalized adamantanes. Cage nitrooxy derivatives have already been used as starting materials to develop preparative methods for the synthesis of structurally diverse compounds [10–24], which have already found (or could find) application in the preparation of materials and biologically active compounds [25–28]. Some polyfunctional adamantanes with a nitrooxy group on the carbon skeleton showed biological activity [29–32]. Nitrooxy derivatives of cage compounds are generally synthesized by the action of nitrogen-containing electrophiles and oxidants. Methods have been proposed for the synthesis of a wide range of nitrooxy
derivatives by reactions of cage hydrocarbons and their functional derivatives with nitric acid and its mixtures [33–44], and the kinetics of nitroxylation have been studied [45, 46]. One-electron transfer from adamantane to nitronium cation gives rise to adamantyl radical cation [47] which undergoes deprotonation to adamantyl radical, and the latter is rapidly oxidized with NO2+ to the corresponding carbenium ion. However, some features of the nitroxylation process related to the solvent nature and state of nitric acid in
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