1,2,3-Benzothiadiazoles. Part I. A simplified synthesis of 1,2,3-benzothiadiazoles

Thiadiazoles

“…indicates that there is a little conjugation between the two rings [15]. Similar values of bond angles and bond lengths have been reported for benzo-1,2,3-thiadiazole 9 [5]. X-Ray data have also been reported for the mesoionic 5-(methoxycarbonyl)amino-3-methyl-1,2,3-thiadiazole (15) and for 4-phenyl-1,2,3-thiadiazole 3-oxide (16) [6].…”

“…Other 1,2,3-thiadiazoles are soluble in methylene chloride and chloroform. Benzo-fused analogues of 1,2,3-thiadiazoles 7 have also been reported [5]. Fully aromatic mesoionic compounds have been synthesized [6], but information is limited.…”

“…1,2,3-Thiadiazoles are weak bases and form a deliquescent hydrochloride salt that is decomposed by water. There are several examples of reactions of alkyl halides at the nitrogen atoms of 1,2,3-thiadiazoles to give salts or mesoionic compounds [5]. Alkylation reactions occur preferentially at N3 ring atom; Table 14.5 shows the effect exerted by substituents at the 4 and 5-position of the ring with the relative formation of compounds 223 and 224.…”

“…Many biologically active derivatives of this ring system have been synthesized and incorporated into commercial drugs and pesticides. For instance, the 1,2,5-thiadiazole timolol (5), is used as maleate salt to treat glaucoma; the sulfonamide derivative, acetazolamide 6, is a diuretic. isomeric thiadiazoles is continuously increasing, there is a gap of knowledge in the area of 1,2,3-thiadiazoles, which still account for the fewest literature citations.…”

A straightforward synthesis of 2-aminobenzothiazoles from Herz compounds

“…For instance, treatment of Herz salts (2) with excess of nitrous acid was reported to give 1,2,3-benzothiadiazoles. 16 On the other hand, malononitrile 17 and amines 18 have been reported to react with the benzene ring of 1,2,3-benzodithiazolium chlorides (2) in low to moderate yields.…”