Two new methods for the synthesis of 2-aminothiazolonesfrom 2-(4-methoxybenzylthio)acetic acids are described. Asingle reagent and simple experimental conditions are usedin the key tandem deprotection−cyclization process. In thefirst approach 2-aminothiazolones are directly accessed viacyclization of the corresponding N-acylisothioureas. Thesecond complementary approach provides access to a varietyof 2-thiomethylthiazolones via cyclization of N-acyldithioimidates. The product 2-thiomethylthiazolones are thenefficiently converted to 2-aminothiazolones via amine displacement.