Ring‐Opening Reactions of Mesoionic [1,2,4]Triazolo[1,5‐c]quinazolines. – Preparation of 1,2,4‐Triazolo[3,4‐b][1,3,4]thiadiazoles by a Translocative Rearrangement

Abstract

1‐Amino‐5‐aryl‐2‐mercapto‐1H[1,2,4]triazolo[1,5‐c]quinazolin‐4‐ium hydroxides, inner salts (1) undergo ring opening by the action of hydrochloric acid to give 4‐amino‐3‐[2‐(aroylamino)‐phenyl]‐4,5‐dihydro‐5‐thioxo‐1H‐1,2,4‐triazoles 3. Reaction of compounds 3 with phosphorus pentasulfide yields the corresponding 1,2,4‐triazolo[3,4‐b][1,3,4]thiadiazoles 6. The molecular structure of 6b has been solved by X‐ray diffraction methods.

3-(2-Ethoxyphenyl)-6-phenyl-1,2,4-triazolo[3,4-b][1,3,4]thiadiazole

“…Bond lengths and angles within the heterocyclic system (Table 1) agree well with the values reported in the literature (Fornies-Marquina et al, 1974;Molina et al, 1989;Zhang et al, 1996;Chen et al, 2000;Dong et al, 2002). The bond lengths indicate some degree of delocalization around the ring system, with the three C N bonds averaging 1.302 (3) Å and the N-N bonds ranging from 1.375 (2) to 1.404 (3) Å .…”

Dichloridobis(methanol-κO)bis(6-methyl-3-phenyl-1,2,4-triazolo[3,4-b][1,3,4]thiadiazole-κN1)cadmium(II)

“…For related literature, see: Fornies-Marquina et al (1974); Huang et al (2005); Molina et al (1989); Naveen et al (2006).…”

“…(2007). E63, m2297 The molecular structure of 6-methyl-3-phenyl-[1,2,4]triazolo(3,4 -b)-1,3,4-thiadiazole (Fornies-Marquina et al, 1974) and its substituted derivatives (Molina et al, 1989;Huang et al, 2005;Naveen et al, 2006) have been reported, however, no metal complexes of these ligands have so far been reported. In this paper, we report the crystal structure of the title compound, (I), a Cd complex obtained by the reaction of 6-methyl-3-phenyl-[1,2,4]triazolo(3,4 -b)-1,3,4-thiadiazole with cadmium chloride in methanol solution.…”

Dibromidobis(6-methyl-3-phenyl-s-triazolo[3,4-b][1,3,4]thiadiazole-κN1)copper(II)

“…For related literature, see: Fornies-Marquina et al (1974); Molina et al (1989); Huang et al (2005); Naveen et al (2006).…”