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13.9.2.1.1.1 Method 1: From 2-Aminobenzenethiols

DOI: 10.1055/sos-SD-013-00386

Wilkins, D. J.; Bradley, P. A.Science of Synthesis, (200413268.

The simplest and most common process for the synthesis of 1,2,3-benzothiadiazoles is through the diazotization of 2-aminobenzenethiols. Jacobson prepared the parent compound, 1,2,3-benzothiadiazole in this way,[‌18‌] and later extended the reaction to naphtho derivatives.[‌57‌,‌58‌] The 1,2,3-benzothiadiazole is typically formed by diazotization of the 2-aminobenzenethiol with nitrous acid (Scheme 20). Jacobson also reported that 1,2,3-benzothiadiazole is formed on boiling diazotized bis(2-aminophenyl) disulfide in water.[‌18‌] Diazotization of 2-[(phenylsulfanyl)methyl]aniline in water results in the formation of 1,2,3-benzothiadiazole through an initial debenzylation of the sulfide.[‌59‌,‌60‌] Cadogan and co-workers reported the preparation of 1,2,3-benzothiadiazole (36, R1=H) in 70% yield by the thermal decomposition of the diazonium acetates, which avoids the variable yields sometimes experienced in the diazotization of 2-aminobenzenethiols.[‌61‌] Other methods of preparing 2-aminobenzenethiols have been well documented, and include displacement reactions of 2-chloroanilines with sodium sulfide, and reduction of 2-nitrobenzenethiol (see HoubenWeyl, Vol.E 8d, p59). A variety of heterocyclic rings have been fused onto the 1,2,3-thiadiazole ring using this method. For example, 1,2,3-thiadiazolopyrimidines have been synthesized by reaction of aminopyrimidinethiols with sodium nitrite and hydrochloric acid.[‌62‌]

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