Proceedings - Interdisciplinary Center for Nanotoxicity

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104 Conference on Current Trends in Computational Chemistry 2009 Mechanism of Aryl Azide Addition to Substituted Norbornene Imides: Effect of Acid Catalysis to the Reaction Pathways T.Petrova, a,b I. Borisenko b, S.Okovytyy, a,b L. Gorb, a I.Tarabara, b J.Leszczynski a a Interdisciplinary Center forNanotoxicity, Department of Chemistry and Biochemistry, Jackson State University, Jackson, MS 39217, USA b Department of Organic Chemistry, Dnepropetrovsk National University, Dnepropetrovsk 49625, Ukraine Development of synthetic approaches and theoretical investigation of mechanisms for reactions of new biologically active nitrogen containing norbornene derivatives due to transformation of different reaction centers of molecules is one of important problems of organic chemistry for heterocyclic compounds. For example, aziridination of carbon double bond (C=C) in some norbornene compounds results in generation of polycyclic triazolines and/or aziridines possessing antineoplastic and antiviral acitivities. Understanding the mechanisms of actual chemical transformations of this type of compounds is a great challenge and source of inspiration for both experimentalists and theoreticians. According to available experimental data the addition of aryl azide (p‐NO2C6H4N3) to various norbornene imide derivatives (1,2) resulted in exo‐triazoline formation. Unexpectedly, reaction of imide bearing the acid substituent at the nitrogen atom (3) with aryl azide led to the formation of azidine polycyclic system as the major product. In order to explain the nature of transformations a quantum‐chemical investigation of possible reaction pathways for the aryl azide addition to norbornene imides (1‐3) and catalytic effect of carboxylic acid in the course of reaction has been performed. O O N C O R p-NO 2C 6H 4N 3 CHCl 3 R = -OCH 3 (1), -NHCH 2C 6H 5 (2) 3 O O N COOH p-NO 2C 6H 4N 3 CHCl 3 O 2N O 2N N N N N O O N C O O O N R COOH All calculations have been performed at the B3LYP/6‐31+G(d) level of theory in the gas phase and in the presence of chloroform as solvent (Polarizable Continuum Model). The addition of azides to bicyclic imides affords either exo‐triazolines or exo‐aziridine depending on nature of imide substuituent. The steric bulk of the azide does not appear to play a significant
Conference on Current Trends in Computational Chemistry 2009 role in the course of the reaction. However, the reactivity of azide was varied significantly due the presence of carboxylic group in endic imide (3). The reaction starts from the concerted [3+2] cycloaddition process to produce triazoline structure. The proton of carboxylic group at initial imide (3) promotes formation of strong hydrogen bonds with nitrogen atoms in triazoline cycle. This bonding favors the opening of triazoline cycle and nitrogen molecule (N2) abstraction with subsequent aziridine cycle formation due to decreasing of activation barrier values. Thus presence of carboxylic group at reactant (3) leads to formation of aziridine as reaction product due to intermolecular acid catalysis. 105
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Proceedings - Interdisciplinary Center for Nanotoxicity

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