PEG-assisted two-component approach for the facile synthesis of 5-aryl-1,2,4-triazolidine-3-thiones under catalyst-free conditions

Abstract

A straightforward and greener PEG-assisted protocol has been disclosed for the synthesis of 5-aryl-1,2,4-triazolidine-3-thiones via the reaction of aromatic aldehydes and thiosemicarbazides using very convenient neutral reaction conditions.

Transalkylidation reaction: green, catalyst-free synthesis of thiosemicarbazones and solving the NMR conflict between their acyclic structure and intramolecular cycloaddition products

“…Cyclocondensation of thiosemicarbazide with aldehydes could afford either 1,2,4-triazolidine-3-thiones or 2-amino-1,3,4-thiadiazoline using different reaction conditions (45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55)(56). We observed that there is a structural elucidation confusion between the open structure of thiosemicarbazone and their cycloaddition product with aldehyde.…”

“…That was obvious in several published articles which reported identical spectral data for both thiosemicarbazones and their cycloaddition product (1,2,4-triazolidine-3-thiones). Thus, many authors incorrectly interpreted the NMR spectral data of alkylidene thiosemicarbazones and reported them as triazolidine-3-thiones (45)(46)(47)(48)54,55,57), this confusion arises from the presence of three exchangeable N-H signals in both structures. Herein, we would like to report a green and simple method for synthesis of alkylidene thiosemicarbazide and clarify the structural elucidation confusion between alkylidene thiosemicarbazide, and their cyclized forms.…”

Thiamine Hydrochloride Catalyzed Synthesis of 1,2,4‐Triazolidine‐3‐thiones in Aqueous Medium

“…General experimental procedure for the synthesis of 1,2,4triazolidine-3-thiones and structure elucidation of novel 1,2,4triazolidine-3-thiones using IR, 1 H and 13 C NMR and Mass is provided in the supporting information. Sulfamic acid [23] (20) EtOH Reflux 30 92 2 [C 16 MPy]AlCl 3 Br [25] (10) H 2 O RT 10 96 3 Catalyst free [31] EtOH 80 15 94 4 N,N-dimethylpyridine-4-amine [24] (20) H 2 O RT 20 95 5 Catalyst free [29] PEG Catalyst free [30] Glycerol 40 96 95 9…”

“…Amongst these, the simplest approach for the synthesis of 1,2,4‐triazolidine‐3‐thiones involves the reaction of aldehydes or ketones with thiosemicarbazides in the presence of catalysts such as sulfamic acid, N,N‐dimethylpyridine‐4‐amine, [C 16 MPy]AlCl 3 Br, [(Py) 2 SO][HSO 4 ], [HMPBSA]HSO 4 , glycine nitrate . Moreover, organic solvents like PEG‐400, glycerol and ethanol endorsing catalyst free conditions have also been reported. However, many of the reported methods suffer from drawbacks like use of toxic catalysts, high reaction temperature, prolong reaction time, expensive precursors, limited substrates etc.…”

An efficient synthesis of anti-microbial 1,2,4-triazole-3-thiones promoted by acidic ionic liquid

“…Earlier, MnO 2 , FeCl 3 , H 2 O 2 and m-chloroperbenzoic acid have been used for synthesis of 1,2,4-triazolidine-4-thiones from steroidal and non-steroidal homocyclic ketone and thiosemicarbazones [36][37][38][39][40][41][42][43]. Recently PEG-assisted synthesis of 5-aryl-1,2,4-triazolidine-3-thiones from aldehydes or cyclic ketones has been reported [44].…”