From N‐Substituted Thioamides to Symmetrical and Unsymmetrical 3,4,5‐Trisubstituted 4H‐1,2,4‐Triazoles: Synthesis and Characterisation of New Chelating Ligands

Abstract

An improved protocol for the synthesis of N-substituted pyridine-2-thiocarboxamides under the conditions of the Willgerodt−Kindler reaction, employing a catalytic amount of sodium sulfide nonahydrate, has been developed. Following this protocol, eight thioamides carrying aromatic or aliphatic N-substituents have been prepared in good to excellent yields. Condensation of these thioamides or their S-alkylated

Five‐Membered Heterocycles with Three Heteroatoms: Triazoles

“…been reported; derivatives 185 were obtained with higher regioselectivity when aromatic and sterically bulky hydrazines were used (Scheme 12.61) [234]. S-Ethyl thioamides 186 react with acyl hydrazides 187 in refluxing n-butanol to give 3,4,5-trisubstituted 4H-1,2,4-triazoles 188 (Scheme 12.62) [235]. An efficient synthesis of substituted 1,2,4-triazoles involved condensation of benzoyl hydrazides with thioamides under microwave irradiation [236] cyclize, and release preparation of 3-thioalkyl-1,2,4-triazoles mediated by the polymer-bound base P-BEMP has been described [240].…”

A Structural Investigation of Anion–Triazole Interactions: Observation of “π‐Pockets” and “π‐Sandwiches”

“…[24,25] Given that we have established a general synthetic route to 4-substituted 3,5-di(2-pyridyl)-1,2,4-triazole Rdpt ligands, [26] we attempted to distinguish between the ligand fields imposed by these ligands using UV/Vis spectroscopy. Hence, we recorded both the solution and solid-state UV/Vis spectra of the nickel(II) complexes 1BF 4 and 2BF 4 Ϫthe ligands adpt and pldpt having triazole N 4 -substituents that differ markedly in their electron-donating/-withdrawing properties (to give a general feel for this difference the Hammett constants are: NH 2 , para: -0.66, ortho: -0.16; pyrrolyl, σ 1 = 0.17 [27] )Ϫin the expectation that this would inform the subsequent iron(II) chemistry of these ligands.…”

New Binding Modes of 1‐Acetyl‐ and 1‐Benzoyl‐5‐hydroxypyrazolines – Synthesis and Characterization of O,O′‐Pyrazoline‐ and N,O‐Pyrazoline‐Zinc Complexes

“…Dimethylzinc solution (1.2 m in toluene purchased from Aldrich) was used without further manipulation. 1 Acetohydrazide (6a): [12] Hydrazine monohydrate (0.20 mol) was added to a solution of ethyl acetate (0.19 mol) in ethanol (50 mL) at room temperature. After refluxing the mixture for 6 h the solvent was removed under vacuum and the colorless residue was dried under high vacuum; yield 10.3 g (87 %, colorless crystals).…”