1,2,3-Benzothiadiazole

1,2,3-Benzothiadiazole is a bicyclic aromatic chemical composed of a benzene ring that is fused to a 1,2,3-thiadiazole. A colorless solid, the compound is soluble in organic solvents.

1,2,3-Benzothiadiazole
Names
Preferred IUPAC name
1,2,3-Benzothiadiazole
Other names
  • Benzothiadiazole
  • Benzthiadiazole
  • Azabenzothiadiazole
  • benzo-1,2,3-thiadiazole
Identifiers
3D model (JSmol)
ChemSpider
EC Number
  • 205-989-4
MeSH benzo-1,2,3-thiadiazole
UNII
  • InChI=1S/C6H4N2S/c1-2-4-6-5(3-1)7-8-9-6/h1-4H
    Key: FNQJDLTXOVEEFB-UHFFFAOYSA-N
  • C1=CC=C2C(=C1)N=NS2
Properties
C6H4N2S
Molar mass 136.17 g·mol−1
Appearance colorless solid
Density 1.499 g/cm3[1]
Melting point 36–37 °C (97–99 °F; 309–310 K)
Boiling point 220.5 °C (428.9 °F; 493.6 K)
Related compounds
Related compounds
 2,1,3-Benzothiadiazole
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Preparation

1,2,3-Benzothiadiazole is readily prepared by the diazotisation reaction of 2-aminothiophenol or its disulfide with sodium nitrite, as originally reported in 1887[2] and reviewed in several subsequent publications.[3][4][5][6]

By the Herz reaction anilines can be converted to benzothiadiazole. The method is attractive since less elaborate precursors (merely anilines) are required. Upon treatment with disulfur dichloride, the anilines give the intermediate 1,3,2-benzothiazathiolium salt, which is diazotised to complete the formation of a 1,2,3-benzothiadiazole. The parent system cannot be made this way, since the use of aniline in this reaction leads to formation of the 6-chloro derivative.[7]

Structure and bonding

The molecule is planar. The N-N and S-N distances are respectively 128 and 171 picometers, indicative of multiple bond character.[1] Like naphthalene, this heterocycle is a 10-electron system.[3]

Reactions

1,2,3-benzothiadiazole is much less nucleophilic than naphthalene. Nitration is slow.[8] For that reason, many of its simple derivatives have been made from 2-aminothiophenols already having additional substituents.[7]

1,2,3-benzothiadiazole is a very weak base and alkylation reactions give exclusively the 3-amino quaternary salt.[9]

Applications

1,2,3-benzothiadiazole has been claimed to synergise insecticides including dicrotophos[10] but has not been commercialised for that application. The only derivative to have found significant use is the fungicide acibenzolar-S-methyl.

References
  1. Mayr, Armin J.; Carrasco-Flores, Benjamin; Cervantes-Lee, Francisco; Pannell, Keith H.; Párkányi, László; Raghuveer, Krishan (1991). "Transition metal heterocyclic chemistry: XI. Manganese cyclopentadienyldicarbonyl complexes of 1,2,3-selena- and thiadiazoles including structural comparison of free and complexed 1,2,3-benzothiadiazole and 4-phenyl-1,2,3-thiadiazole". Journal of Organometallic Chemistry. 405 (3): 309–322. doi:10.1016/0022-328X(91)86290-7.
  2. Jacobson, J. (1887). "Zur Kenntniss der orthoamidirten aromatischen Mercaptane". Berichte der Deutschen Chemischen Gesellschaft. 20: 1895–1903. doi:10.1002/cber.188702001423.
  3. Hodgson, H.H.; Dodoson, D.P. (1964). "A Review of the Chemistry of the Arylthiadiazoles or Internal Diazo–Sulphides". Journal of the Society of Dyers and Colourists. 64 (2): 65–71. doi:10.1111/j.1478-4408.1948.tb02498.x.
  4. Thomas, E.W. (1984). "1,2,3-Thiadiazoles and their Benzo Derivatives". Comprehensive Heterocyclic Chemistry. pp. 447–462. doi:10.1016/B978-008096519-2.00092-8. ISBN 9780080965192.
  5. Storr, R. C.; Gilchrist, T. L., eds. (2004). "Product Class 9: 1,2,3-Thiadiazoles". Science of Synthesis. Vol. 13: Category 2, Hetarenes and Related Ring Systems. doi:10.1055/sos-SD-013-00386. ISBN 9783131122810.
  6. "1,2,3-Benzothiadiazole". 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. pp. 93–104. ISBN 9783131812445.
  7. Kirby, P.; Soloway, S. B.; Davies, J. H.; Webb, Shirley B. (1970). "1,2,3-Benzothiadiazoles. Part I. A simplified synthesis of 1,2,3-benzothiadiazoles". Journal of the Chemical Society C: Organic (16): 2250. doi:10.1039/J39700002250.
  8. Ward, E. R.; Heard, D. D. (1963). "1,2,3-Benzothiadiazole. Part II. Electrophilic substitution in 4- and 6-amino-1,2,3-benzothiadiazoles". Journal of the Chemical Society (Resumed): 4794–4803. doi:10.1039/JR9630004794.
  9. Jaffari, G. A.; Nunn, A. J.; Ralph, J. T. (1970). "1,2,3-Benzothiadiazole. Part VI. Investigations on the quaternisation of 1,2,3-benzothiadiazole and 1,2,3-benzoselenadiazole". Journal of the Chemical Society C: Organic (15): 2060. doi:10.1039/J39700002060.
  10. Felton, John C.; Jenner, Donald W.; Kirby, Peter. (1970). "Benzothiadiazoles, a novel group of insecticide synergists". Journal of Agricultural and Food Chemistry. 18 (4): 671–673. doi:10.1021/jf60170a011.
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