4,6-dichloro-5-nitrobenzofuroxan: Different polymorphisms and dft investigation of its reactivity with nucleophiles

Chugunova E. Akylbekov N. Dobrynin A. Burilov A. Boga C. Micheletti G. Frenna V. Mattioli E.J. Calvaresi M. Spinelli D.
December-2 2021 MDPI

International Journal of Molecular Sciences
2021 #22 Issue 24

This research focuses on the X-ray structure of 4,6-dichloro-5-nitrobenzofuroxan 1 and of some of its amino derivatives (4a, 4e, 4g, and 4l) and on DFT calculations concerning the nucleophilic reactivity of 1. We have found that by changing the solvent used for crystallization, it is possible to obtain 4,6-dichloro-5-nitrobenzofuroxan (1) in different polymorphic structures. Moreover, the different torsional angles observed for the nitro group in 1 and in its amino derivatives (4a, 4e, 4g, and 4l) are strictly dependent on the steric hindrance of the substituent at C-4. DFT calculations on the course of the nucleophilic substitution confirm the role of the condensed furoxan ring in altering the aromaticity of the carbocyclic frame, while chlorine atoms strongly influence the dihedral angle and the rotational barrier of the nitro group. These results corroborate previous observations based on experimental kinetic data and give a deep picture of the reaction with amines, which proceeds via a “non-aromatic” nucleophilic substitution.

Benzofuroxans , DFT calculations , Nucleophilic substitutions , Polymorphism , X-ray structures

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Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Akad. Arbuzov st. 8, Kazan, 420088, Russian Federation
Laboratory of Plant Infectious Diseases, FRC Kazan Scientific Center of Russian Academy of Sciences, Lobachevskogo st. 2/31, Kazan, 420111, Russian Federation
Laboratory of Engineering Profile “Physical and Chemical Methods of Analysis”, Korkyt Ata Kyzylorda University, Aitekebie str. 29A, Kyzylorda, 120014, Kazakhstan
Institute of Radio Electronics, Photonics and Digital Technologies, Kazan National Research Technical University, 10 Karl Marx Str, Kazan, 420111, Russian Federation
Department of Industrial Chemistry ‘Toso Montanari’ ALMA MATER STUDIORUM, Università di Bologna, Viale del Risorgimento 4, Bologna, 40136, Italy
Department STEBICEF, University of Palermo, Ed.17, Viale delle Scienze, Palermo, 90128, Italy
Department of Chemistry ‘G. Ciamician’ ALMA MATER STUDIORUM, Università di Bologna, Via Selmi 2, Bologna, 40126, Italy

Arbuzov Institute of Organic and Physical Chemistry
Laboratory of Plant Infectious Diseases
Laboratory of Engineering Profile “Physical and Chemical Methods of Analysis”
Institute of Radio Electronics
Department of Industrial Chemistry ‘Toso Montanari’ ALMA MATER STUDIORUM
Department STEBICEF
Department of Chemistry ‘G. Ciamician’ ALMA MATER STUDIORUM

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