Synthesis, Characterization, and Energetic Studies of Polynitro Aryl-1,2,3...
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Energetic Materials Synthesis, Characterization, and Energetic Studies of Polynitro Aryl-1,2,3-2 H-Triazoles Nagarjuna Kommu, [a] A. Sudheer Kumar, [a] J. Raveendra, [a] Vikas D. Ghule, [b] and Akhila K. Sahoo* [a, c] Abstract: A series of energetic polynitro-aryl-1,2,3-2 H-tria- zoles are synthesized from readily accessible aryl-1,2,3-2 H-tri- azoles. X-ray diffraction analysis established the solid-state structures of several representative molecules. The thermal properties are determined by differential scanning calorime- try and thermogravimetric analysis (DSC-TGA) data. Based on computational studies, most of the compounds showed positive heats of formation and the densities were 1.55 to 1.83 g cm 3 . In addition, the compounds were thermally stable (T d > 210 8C) and exhibited acceptable detonation properties. Introduction Triazole motifs are invariably present in many notable energet- ic materials. [1] Thus, design and synthesis of triazole-bearing N- and O-rich energetic materials is always important and receives significant attention. The high nitrogen content of 1,2,3- and 1,2,4-triazoles contributes to high positive heats of formation (HOFs). [2, 3] Interestingly, the heat of formation of the 1,2,3-tria- zole is higher (272 kJ mol 1 ) than 1,2,4-triazole (191 kJ mol 1 ). [4] Therefore, 1,2,3-triazole-based compounds are energetically su- perior than 1,2,4-triazole derivatives. [4] Moreover, 1,2,3-triazole exists in two tautomeric forms: 1,2,3-1 H-triazole and 1,2,3-2 H- triazole. [5] In general, the 1,2,3-1 H-triazole skeleton is reliably constructed involving [3+2]-cycloaddition between readily ac- cessible azides and alkynes in a “click reaction”. [6] Consequently, N- and O-rich 1,2,3-1 H-triazole-bearing molecules are readily synthesized and used in various energetic applications. In con- trast, fabrication of 1,2,3-2 H-triazole-based energetic materials are rare; [7] this is because the selective N-2 substitution in the preparation of 1,2,3-2 H-triazoles is challenging. [8, 9] Surprisingly, the reported 1,2,3-2 H-triazole derivatives are more thermally stable over 1,2,3-1 H-triazoles. [7d] Despite the potential utility of 1,2,3-2 H-triazole moiety, the synthesis of N- and O-rich 1,2,3- 2 H-triazole derivatives for energetic applications is poorly in- vestigated. Moreover, the electronic and symmetry factors pro- mote nitration of the 2 H-triazole moiety in N-aryl/heteroaryls (Scheme 1). In contrast, the 1 H-triazole moiety is unaffected during the nitration of the 1 H-triazole-substituted N-aryl/heter- oaryls (Scheme 1). [2b] Our research interest is aimed at the con- struction of N-, O-, and F-rich small heterocycle energetic ma- terials and this has led us to discuss the design, synthesis, and energetic studies of a wide range of nitro/nitrogen-rich N-aryl/ heteroaryl-1,2,3-2 H-triazole entities, obtained through Pd-cata- lyzed and base-promoted coupling reactions of aryl- and heter- oaryl halides with 1,2,3-triazole followed by a nitration se- quence. The effect of nitration on various functional group decorated aryl(hetero)-1,2,3-2 H-triazoles is also probed. The topologies of the molecular entities are established by X-ray Scheme 1. Electronic effects promoting nitration of the 1,2,3-2 H-triazole moiety. [a] N. Kommu, A. S. Kumar, J. Raveendra, Prof. Dr. A. K. Sahoo Advanced Center of Research in High Energy Materials University of Hyderabad Hyderabad-500046 (India) [b] V. D. Ghule Department of Chemistry National Institute of Technology Kurukshetra-136119, Haryana (India) [c] Prof. Dr. A. K. Sahoo School of Chemistry University of Hyderabad Hyderabad-500046 (India) E-mail : [email protected] [email protected] Homepage: http ://chemistry.uohyd.ac.in/ ~ aks/ Supporting information for this article is available on the WWW under http ://dx.doi.org/10.1002/ajoc.201500390. Asian J. Org. Chem. 2016, 5, 138 – 146 # 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 138 Full Paper DOI: 10.1002/ajoc.201500390
Transcript of Synthesis, Characterization, and Energetic Studies of Polynitro Aryl-1,2,3...
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Energetic Materials
Synthesis, Characterization, and Energetic Studies of PolynitroAryl-1,2,3-2 H-Triazoles
Nagarjuna Kommu,[a] A. Sudheer Kumar,[a] J. Raveendra,[a] Vikas D. Ghule,[b] andAkhila K. Sahoo*[a, c]
Abstract: A series of energetic polynitro-aryl-1,2,3-2 H-tria-zoles are synthesized from readily accessible aryl-1,2,3-2 H-tri-azoles. X-ray diffraction analysis established the solid-state
structures of several representative molecules. The thermal
properties are determined by differential scanning calorime-try and thermogravimetric analysis (DSC-TGA) data. Based
on computational studies, most of the compounds showed
positive heats of formation and the densities were 1.55 to1.83 g cm¢3. In addition, the compounds were thermallystable (Td>210 8C) and exhibited acceptable detonationproperties.
Introduction
Triazole motifs are invariably present in many notable energet-
ic materials.[1] Thus, design and synthesis of triazole-bearing N-and O-rich energetic materials is always important and receives
significant attention. The high nitrogen content of 1,2,3- and1,2,4-triazoles contributes to high positive heats of formation
(HOFs).[2, 3] Interestingly, the heat of formation of the 1,2,3-tria-
zole is higher (272 kJ mol¢1) than 1,2,4-triazole (191 kJ mol¢1).[4]
Therefore, 1,2,3-triazole-based compounds are energetically su-
perior than 1,2,4-triazole derivatives.[4] Moreover, 1,2,3-triazoleexists in two tautomeric forms: 1,2,3-1 H-triazole and 1,2,3-2 H-
triazole.[5] In general, the 1,2,3-1 H-triazole skeleton is reliablyconstructed involving [3++2]-cycloaddition between readily ac-cessible azides and alkynes in a “click reaction”.[6] Consequently,
N- and O-rich 1,2,3-1 H-triazole-bearing molecules are readilysynthesized and used in various energetic applications. In con-trast, fabrication of 1,2,3-2 H-triazole-based energetic materialsare rare;[7] this is because the selective N-2 substitution in the
preparation of 1,2,3-2 H-triazoles is challenging.[8, 9] Surprisingly,
the reported 1,2,3-2 H-triazole derivatives are more thermallystable over 1,2,3-1 H-triazoles.[7d] Despite the potential utility of
1,2,3-2 H-triazole moiety, the synthesis of N- and O-rich 1,2,3-2 H-triazole derivatives for energetic applications is poorly in-
vestigated. Moreover, the electronic and symmetry factors pro-mote nitration of the 2 H-triazole moiety in N-aryl/heteroaryls
(Scheme 1). In contrast, the 1 H-triazole moiety is unaffected
during the nitration of the 1 H-triazole-substituted N-aryl/heter-oaryls (Scheme 1).[2b] Our research interest is aimed at the con-
struction of N-, O-, and F-rich small heterocycle energetic ma-terials and this has led us to discuss the design, synthesis, and
energetic studies of a wide range of nitro/nitrogen-rich N-aryl/
heteroaryl-1,2,3-2 H-triazole entities, obtained through Pd-cata-lyzed and base-promoted coupling reactions of aryl- and heter-
oaryl halides with 1,2,3-triazole followed by a nitration se-quence. The effect of nitration on various functional group
decorated aryl(hetero)-1,2,3-2 H-triazoles is also probed. Thetopologies of the molecular entities are established by X-ray
Scheme 1. Electronic effects promoting nitration of the 1,2,3-2 H-triazolemoiety.
[a] N. Kommu, A. S. Kumar, J. Raveendra, Prof. Dr. A. K. SahooAdvanced Center of Research in High Energy MaterialsUniversity of HyderabadHyderabad-500046 (India)
[b] V. D. GhuleDepartment of ChemistryNational Institute of TechnologyKurukshetra-136119, Haryana (India)
[c] Prof. Dr. A. K. SahooSchool of ChemistryUniversity of HyderabadHyderabad-500046 (India)E-mail : [email protected]
[email protected]: http ://chemistry.uohyd.ac.in/~aks/Supporting information for this article is available on the WWW underhttp ://dx.doi.org/10.1002/ajoc.201500390.
Asian J. Org. Chem. 2016, 5, 138 – 146 Ó 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim138
Full PaperDOI: 10.1002/ajoc.201500390
http://dx.doi.org/10.1002/ajoc.201500390
