Mercaptoacetic acid (3), also known as thioglycolic acid, is a liquid miscible with water and with most organic solvents such as alcohols, ether, chloroform and benzene.[ 1 ] It is widely described in the literature, especially as a substrate for the synthesis of pharmacologically active heterocycles[ 2 ] including 1,3-thiazolidin-4-ones,[ 3 ] 1,4-thiazepines[ 4 ] and thiazoles.[ 5 ] It is also used for the formation of spiro derivatives,[ 6 ] in multicomponent reactions, and in removing the nosyl protecting group from amine functions of α-amino acids.[ 7 ]