An Efficient, One-Pot Synthesis of 3-Methyl-1,3-thiazolidines

3-Methyl 1,3-thiazolidines 3a-c can be prepared easily in good yields by the reaction of β-mercaptoamine derivatives 1a-c with formalin and formic acid in a one-pot operation. The same procedure is also suitable for the construction of the 3-methyl-tetrahydro-1,3-thiazine skeleton from γ-mercaptoamines as exemplified in the synthesis of 3d.