Expedient synthesis of novel antibacterial hydrazono-4-thiazolidinones under catalysis of a natural-based binary ionic liquid.

A library of pyran-2H-one-3-ylmethylidene and chromene-2H-one-3-ylmethylidene derivatives of the titled heterocyclic framework was synthesized from 3-acyl-4-hydroxypyran/chromene-2H-one via sequential reaction with thiosemicarbazide and dialkyl acetylenedicarboxylates. The syntheses were carried out under efficient catalysis of a new binary ionic liquid mixture [L-prolinium chloride][1-methylimidazolium-3-sulfonate] in one pot and solvent-free conditions. Calculations based on density functional theory displayed that the barrier energy for interconversion of the two possible diastereomeric isomers of each product is less than the thermal energy of molecules at room temperature, as only one product can be resolved from a given reaction mixture.