Renewable Task‐Specific Acidic Ionic Liquid [NMP]H ₂ PO ₄ : Ultrasonication‐Assisted One‐Pot Four Component Synthesis of Quinoxaline–Thiazole/1,3,4‐Thiadiazine Hybrids and In‐Silico ADMET Predictions

A renewable task‐specific acidic ionic liquid, N ‐methyl‐2‐pyrrolidonium dihydrogen phosphate ([NMP]H 2 PO 4 ), was employed as a recyclable catalyst for the ultrasonication‐assisted, one‐pot, four‐component synthesis of novel quinoxaline–thiazole and quinoxaline–1,3,4‐thiadiazine hybrids. The methodology integrates ninhydrin, o ‐phenylenediamine, thiosemicarbazide/thiocarbohydrazide, and α ‐bromoacetophenone derivatives under solvent‐free conditions, delivering the target products in high yields and short reaction times. Reaction parameters, including catalyst loading, ultrasonic frequency, and bath temperature, were systematically optimized, with 15 mol% [NMP]H 2 PO 4 at 75°C and 50 kHz affording optimal conversions. The catalyst was readily recovered and reused over four cycles with minimal loss in activity. In‐silico ADMET and TOPKAT analyses revealed that most compounds complied with Veber's rule and exhibited acceptable drug‐likeness profiles, with the quinoxaline–1,3,4‐thiadiazine series showing comparatively lower predicted toxicity than their thiazole counterparts. This green synthetic approach offers an efficient and sustainable route to multifunctional heterocyclic scaffolds with promising pharmacological potential.