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The general procedure for the synthesis of benzo[d][1,2,3]thiadiazole from 2-aminothiophenol was as follows: o-aminothiophenol (0.3 mmol, 1 eq.) and tert-butyl nitrite (0.45 mmol, 1.5 eq.) were sequentially added to the reaction vessel at room temperature (25 °C), followed by the addition of 2 mL of water as reaction solvent. The reaction mixture was stirred at 25 °C for 3 min. After the reaction was completed, 10 mL of ethyl acetate was added to dilute the reaction solution, and the diluted solution was transferred to a partition funnel and extracted with saturated saline to separate the aqueous and organic phases. The aqueous phase was then extracted with ethyl acetate 2 to 4 times. All organic phases were combined and dried with 5 g of anhydrous sodium sulfate for 5 min, followed by filtration. The filter cake was washed with ethyl acetate (5 mL x 3 times) and then concentrated under reduced pressure. Finally, the concentrate was separated by column chromatography (eluent was petroleum ether to ethyl acetate 3:1 by volume) and the eluate was collected. After removing the solvent, a white liquid product was obtained in 96% yield.

1,2,3-Benzothiadiazole crystallises from pet ether, and has at 264 and 306nm in hexane. [Overberger et al. J Org max Soc 24 1407 1959, Beilstein 27 III/IV 7113.]

[1] Synthesis, 2011, # 13, p. 2154 - 2158
[2] Patent: CN107311960, 2017, A. Location in patent: Paragraph 0044-0047; 0144-0147
[3] Patent: WO2011/100502, 2011, A1. Location in patent: Page/Page column 48-49
[4] Phosphorus and Sulfur and the Related Elements, 1984, vol. 19, p. 279 - 284
[5] Justus Liebigs Annalen der Chemie, 1893, vol. 277, p. 227,228