Synthesis of thiazolidines using ionic liquids as a green catalyst and media: recent advances

Thiazolidines (TZs) are a significant class of heterocyclic compounds displaying several pharmaceutical, and biological activities. Because of our interest in the chemistry and biology of heterocycles, with the exploitation of ionic liquids (ILs) in organic transformations, herein, the recent preparative developments for TZs in ILs are deliberated wherein ILs play the dual role of solvent and catalysts. The preparation of various types of TZs, namely 1,3-thiazolidine-4-ones bearing azo-linkage, spiro-[indole-thiazolidine]-2,4'-diones, 2-(2-oxo-chromenyl)-3-thiazolidinones, 2-pyrazolo-thiazolidineones, 2-imino-thiazolidine, and pyridine-based 5-amino-2-oxo-thiazolo[4,5-b] pyridine-6-carbonitriles has been described using various ILs. This review aims at the synthesis advancement in the assembly of TZs in ILs during 2012-2023, under various conditions such as reflux, stirring, solvent-free or microwave, and ultrasound irradiation conditions. Devoid of vapor pressure, and being recyclable, ILs are relatively eco-friendly, especially for inherently sustainable multi-component reactions (MCRs) that are atom-economic and are endowed with waste reduction attributes in terms of fewer manipulations.