Ultrasound Accelerated Synthesis of 2‐Amino‐1,3‐Thiazoles via Three‐Component Reaction of Methyl Ketones, Thioureas, and N‐Bromosuccinimide Catalyzed by Brønsted Acidic Ionic Liquid

ABSTRACT The direct synthesis of the 2‐amino‐1,3‐thiazole scaffold has been achieved via a three‐component reaction between methyl ketones, thioureas, and N‐bromosuccinimide, efficiently promoted by 1‐(4‐sulfobutyl)‐3‐methylimidazolium hydrogen sulfate among Lewis acidic triflate salts, solid acids, and Brønsted acidic ionic liquids. Under ultrasound assistance, 16 2‐amino‐1,3‐thiazoles were synthesized in yields ranging from 20% to 78% in 35 to 115 min, depending on the substituents of aromatic ketones and thioureas. Additionally, the recovery yield and recycling of 1‐(4‐sulfobutyl)‐3‐methylimidazolium hydrogen sulfate were achieved at 82% and five times, respectively, without significantly affecting the yield of 2‐amino‐4‐phenyl‐1,3‐thiazole.