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
