Synthesis of Thiazolo[3,2‐b] [1,2,4]triazoles through Pd‐Catalyzed Copper‐Free Sonogashira Coupling Reaction

Abstract

The synthesis of 2-substituted thiazolo [3,2-b] [1,2,4]triazoles is accomplished copper-free, Pd-catalyzed Sonogashira reaction of 6-(iodomethyl)-2-methylthiazolo[3,2-b][1,2,4]triazole with terminal alkynes in DMF at 70°C. The coupling reaction of phenylacetylene and 4-ethynyltoluene gave the desired products in high yields. While, the Sonogashira reaction of alkynes such as 1-hexyne, 1-octyne, propargyl alcohols, and propargyl amines afforded the products in good yields.ChemistrySelect 2019, 4, 9238 -9240

Copper-free Sonogashira cross-coupling reactions: an overview

“…Although, the Sonogashira coupling of various alkynes, for example, propargyl alcohols, 1-octyne, and propargyl amines gave the corresponding products in satisfactory yields (Scheme 34). 96 Sardarian and co-workers in 2019 demonstrated the formation of a new heterogenized organometallic catalyst through coordinating Pd with polyvinyl alcohol-substituted Fe 3 O 4 @SiO 2 1-octyne. The reaction of phenylacetylene with different heteroaryl halides having electron-donating and withdrawing groups afforded the relevant products in very high yields.…”

“…Although, the Sonogashira coupling of various alkynes, for example, propargyl alcohols, 1-octyne, and propargyl amines gave the corresponding products in satisfactory yields ( Scheme 34 ). 96 …”

The Use of Electrophilic Cyclization for the Preparation of Condensed Heterocycles

“…62 By contrast, iodination was practically non-stereoselective, leading to the formation of almost equal amounts of E-and Z-stereoisomers. However, Bakherad and co-workers 63 claim that the iodination of propargylic thioethers 109 (R 2 = H) occurs with the formation of [1,3]thiazolo [3,2-b][1,2,4]triazoles 111, which in our opinion is doubtful because the authors 63 provided as evidence only the analysis of NMR spectra in comparison with NMR spectra of known compounds that were quite different in structure.…”

Fused bicyclic 1,2,4‐triazoles with one extra sulfur atom: Synthesis, properties, and biological activity

“…[107] The synthesis of 2-substituted thiazolo [ . [108] The reaction between C-5 lithium thiazolo[3,2-b] [1,2,4]triazoles and enantiomerically pure (S,S)-N-tertbutanesulfinyl-3,3,3-trifluoroacetaldimines leads to the formation of thiazolo[3,2-b][1,2,4]triazoles 54 with chiral (trifluoro)-ethylamine at position 5 (Scheme 42). [109,110] Functionalization of the salts under the influence of nucleophiles and temperature was investigated.…”