Isothiouronium salts as useful and odorless intermediates for the synthesis of thiaalkylimidazolium ionic liquids

• Published in: Tetrahedron letters Vol. 60; no. 11; pp. 780 - 784
• Main Authors: Matiello, Gabriela I., Pazini, Alessandra, da Silva, Kácris I.M., da Costa, Rafaela G.M., Ebeling, Günter, Dupont, Jairton, Limberger, Jones, Scholten, Jackson D.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 14-03-2019
• Subjects: Cross-coupling; Ionic liquids; Isothiouronium salts; Sulfur compounds; Ionic liquids; Sulfur compounds; Isothiouronium salts; Cross-coupling
• ISSN: 0040-4039; 1873-3581
• DOI: 10.1016/j.tetlet.2019.02.013

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•Synthesis of thiaalkylimidazolium ionic liquids from odorless isothiouronium salts.•Mono and dicationic thiaalkylimidazolium ionic liquids were prepared and characterized.•These ionic compounds were applied as ligands in Ullmann and Suzuki coupling reactions.•They can also be employed as charged probes to detect intermediates by ESI-MS.
A simple and odorless route for the synthesis of monocationic and dicationic thiaalkylimidazolium ionic liquids (ILs) is reported. Our approach starts with the selective monoalkylation of dihalogenated substrates by methylimidazole derivatives, followed by the synthesis of odorless isothiouronium salts via reaction with thiourea. The target ILs are obtained after sequential hydrolysis-alkylation of the isothiouronium salts followed by anion metathesis in water. After extraction, the novel thiaalkylimidazolium ILs are obtained with high purity, without the requirement of additional purification steps. In order to demonstrate their applicability, two of these task-specific ILs were employed as ligands in Ullmann and Suzuki couplings and also as charged probes to detect copper intermediates via ESI(+)-MS.