2-Mercaptothiazoline, is used in the chain-lengthening of alkyl halides by trans-iodopropenylenation. 2-Mercaptothiazoline is an antithyroid agent that strongly reduces thyroid hormone levels. 2-Mercaptothiazoline is also used as an intermediate in the preparation of biologically active compounds. It is also used as a tool for highly selective chiral synthesis of penam- and carbapenam-type β-lactam antibiotics.