2,1,3-Benzothiadiazole

2,1,3-Benzothiadiazole is a bicyclic molecule composed of a benzene ring that is fused to a 1,2,5-thiadiazole.

2,1,3-Benzothiadiazole
Names
Preferred IUPAC name
2,1,3-Benzothiadiazole
Other names
  • Piazthiole
  • Benzisothiadiazole
  • Benzo[1,2,5]thiadiazole
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.005.442
EC Number
  • 205-985-2
  • InChI=1S/C6H4N2S/c1-2-4-6-5(3-1)7-9-8-6/h1-4H
    Key: PDQRQJVPEFGVRK-UHFFFAOYSA-N
  • C1=CC2=NSN=C2C=C1
Properties
C6H4N2S
Molar mass 136.17 g·mol−1
Melting point 54.0 °C (129.2 °F; 327.1 K)
Boiling point 203.0 °C (397.4 °F; 476.1 K)
Related compounds
Related compounds
 1,2,3-Benzothiadiazole
Hazards
GHS labelling:
Warning
H315, H319, H335
P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Preparation and structure

2,1,3-Benzothiadiazole has been known since the 19th century. It is readily prepared in at least 85% yield from o-phenylenediamine by reaction with two equivalents of thionyl chloride in pyridine. The by-products are sulfur dioxide and HCl.[1]

There are a number of alternative methods used to make this heterocycle and these have been reviewed.[2][3] The crystal structure of the compound was determined in 1951, when it had the common name piazthiol(e).[4]

Reactions

The extent of the aromaticity of the compound was examined by a study of its proton NMR spectrum and comparison with naphthalene, which allowed the conclusion that it and related oxygen and selenium heterocycles did behave as 10-electron systems in which the 2-heteroatom contributed its lone pair to the ring current, in accordance with Hückel's rule.[5]

As a result, 2,1,3-benzothiadiazole undergoes the standard chemistry of aromatic compounds, for example readily forming nitro[1] and chloro derivatives.[6] The chemistry of this heterocycle and its simple derivatives has been reviewed.[7]

Under reducing conditions, 2,1,3-benzothiadiazoles can be converted back to the 1,2-diaminobenzene compounds from which they were prepared. This can be a useful way to protect a pair of reactive amino groups while other transformations are performed in the benzene ring to which they are attached.[8]

Applications

2,1,3-Benzothiadiazole has been of interest as a redox-active organic component in flow batteries owing to its favourable solubility, low reduction potential and fast electrochemical kinetics.[9]

Such properties in derivatives containing this heterocycle have made it of growing interest in dyestuffs,[10] white light-emitting polymers,[8][11] solar cells,[12] and in luminescence studies.[13]

References
  1. Pesin, V. G.; Sergeev, V. A. (1969). "Research on 2,1,3-thia- and selenadiazole". Chemistry of Heterocyclic Compounds. 3 (5): 662–666. doi:10.1007/BF00468340. S2CID 98830770.
  2. Storr; Gilchrist, eds. (2004). "Product Class 11: 1,2,5-Thiadiazoles and Related Compounds". Category 2, Hetarenes and Related Ring Systems. doi:10.1055/sos-SD-013-00458. ISBN 9783131122810.
  3. Rakitin, Oleg A. (2019). "Recent Developments in the Synthesis of 1,2,5-Thiadiazoles and 2,1,3-Benzothiadiazoles". Synthesis. 51 (23): 4338–4347. doi:10.1055/s-0039-1690679.
  4. Luzzati, Z.Z. (1951). "Structure cristalline de piasélénol, piazthiol et benzofurazane". Acta Crystallographica. 4: 193–200. doi:10.1107/S0365110X51000702.
  5. Fedin, E. I.; Todres, Z. V. (1970). "Studies in the field of aromatic heterocycles" (pdf). Chemistry of Heterocyclic Compounds. 4 (3): 308–313. doi:10.1007/BF00755265. S2CID 91864834.
  6. Pesin, V. G.; d'Yachenko, E. K. (1969). "Researches on 2,1,3-thia-and selenadiazole". Chemistry of Heterocyclic Compounds. 3: 68–70. doi:10.1007/BF00944264. S2CID 100997583.
  7. Houben-Weyl Methods of Organic Chemistry Vol. E 8d, 4th Edition Supplement: Hetarenes III (Five-Membered Rings with Two and More Heteroatoms in the Ring System) - Part 4. 14 May 2014. ISBN 9783131812445.
  8. Neto, Brenno A. D.; Lapis, Alexandre A. M.; da Silva Júnior, Eufrânio N.; Dupont, Jairton (January 2013). "2,1,3-Benzothiadiazole and Derivatives: Synthesis, Properties, Reactions, and Applications in Light Technology of Small Molecules". European Journal of Organic Chemistry. 2013 (2): 228–255. doi:10.1002/ejoc.201201161.
  9. Duan, Wentao; Huang, Jinhua; Kowalski, Jeffrey A.; Shkrob, Ilya A.; Vijayakumar, M.; Walter, Eric; Pan, Baofei; Yang, Zheng; Milshtein, Jarrod D.; Li, Bin; Liao, Chen; Zhang, Zhengcheng; Wang, Wei; Liu, Jun; Moore, Jeffery S.; Brushett, Fikile R.; Zhang, Lu; Wei, Xiaoliang (2017). ""Wine-Dark Sea" in an Organic Flow Battery: Storing Negative Charge in 2,1,3-Benzothiadiazole Radicals Leads to Improved Cyclability". ACS Energy Letters. 2 (5): 1156–1161. doi:10.1021/acsenergylett.7b00261.
  10. Frizon, Tiago Elias Allievi; Valdivia Martínez, Julio César; Westrup, José Luiz; Duarte, Rodrigo da Costa; Zapp, Eduardo; Domiciano, Kelvin Guessi; Rodembusch, Fabiano Severo; Dal-Bó, Alexandre Gonçalves (December 2016). "2,1,3-Benzothiadiazole-based fluorophores. Synthesis, electrochemical, thermal and photophysical characterization". Dyes and Pigments. 135: 26–35. doi:10.1016/j.dyepig.2016.07.011.
  11. Wu, Hongbin; Ying, Lei; Yang, Wei; Cao, Yong (2010). "White-Emitting Polymers and Devices". WOLEDs and Organic Photovoltaics. Green Energy and Technology. pp. 37–78. doi:10.1007/978-3-642-14935-1_2. ISBN 978-3-642-14934-4.
  12. Wang, Yang; Michinobu, Tsuyoshi (2016). "Benzothiadiazole and its π-extended, heteroannulated derivatives: Useful acceptor building blocks for high-performance donor–acceptor polymers in organic electronics". Journal of Materials Chemistry C. 4 (26): 6200–6214. doi:10.1039/C6TC01860B.
  13. Sukhikh, Taisiya; Ogienko, D.; Bashirov, D.; Konchenkoa, S. (May 21, 2019). "Luminescent complexes of 2,1,3-benzothiadiazole derivatives". Russian Chemical Bulletin. 68: 651–661. doi:10.1007/s11172-019-2472-9.
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