Synthesis of some substituted 1,2,4-triazole and 1,3,4-thiadiazole derivatives

Abstract

New S-substituted 1,2,4-triazole and 1,3,4-thiadiazole derivatives have been prepared.We have already reported the synthesis of substituted 1,2,4-triazoles and 1,3,4-thiadiazoles [1], which have a broad spectrum of biological activity as it known from the literature data. Continuing a search for biologically active compounds of this type [2][3][4][5] and in an attempt to clarify the changes in the biological activity of these compounds upon replacing the free mercapto group with various substituents, we undertook the synthesis of a series of new S-substituted triazoles 1a-k and thiadiazole 2., e, f, i-k R = Me, a-d, f-h R 1 = H, e, i-k R 1 = Br, a-e R 2 = Me, f-k R 2 = Ph; a-i R 3 = 3-Br-4-MeOC 6 H 3 , j R 3 = 3-Br-4-i-BuOC 6 H 3 , k R 3 = i-BuThe starting 3,4-disubstituted 5-mercapto-1,2,4-triazoles were obtained in our laboratory by the cyclization of 1-[3-R 1 -4-alkoxyphenylaceto]-4-R 2 -thiosemicarbazides (R 1 = Br or H, R 2 = Me or Ph) in an alkaline medium with subsequent acidification by adding acetic acid [1]. The reaction of these products with 4-alkoxy-3-bromobenzyl chloride or isoamyl chloride in alkaline medium gave S-substituted triazoles 1a-k. The potassium salt of 4-ethoxyphenylacetodithiocarbazic acid [5], which in the presence of concentrated sulfuric acid cyclizes to a 2-substituted 5-mercapto-1,3,4-thiadiazole, was used as the starting compound for the synthesis of S-substituted 1,3,4-thiadiazole 2. The reaction of this mercapto derivative with 3-bromo-4-methoxybenzyl chloride gave compound 2.

Discovery of Small Molecule Kappa Opioid Receptor Agonist and Antagonist Chemotypes through a HTS and Hit Refinement Strategy

“…Beginning with the appropriate isothiocyanate and 2-picolynyl hydrazide, we synthesized the 1,2,4-triazole-3-thione scaffolds in two steps and excellent yields (77−82% overall yields) without chromatographic separations. 28 The subsequent coupling with a wide range of benzyl halides proceeded smoothly in acetone facilitated by K 2 CO 3 29 to readily furnish over 75 compounds, a selection of which is shown in Table 2.…”

Current Developments in the Syntheses of 1,2,4-Triazole Compounds

“…It is well known that thiol groups in triazole thiols have high reactivity, and they can easily react with a series of halides in the presence of base. The reaction of 3,4-disubstituted 5-thiol-1,2,4-triazole 227, which was provided by the intramolecular cyclization of thiosemicarbazides in alkaline medium and subsequent acidification with acetic acid, with benzyl or isoamyl chlorides under basic condition could afford S-substituted triazole 228 in 50-95% yields (Scheme 98) [300]. Researches demonstrated that substituents on benzene ring had large influence on this transformation.…”