The reaction of methyl azidoacetate with several thiocarbonyl compounds at 80°C leads to imine derivatives of methyl glycinate in yields of about 60%. With 2,2,4,4-tetramethyl-3-thioxocyclobutanone, only 19% of the corresponding glycinate 19 is obtained. The main products in this reaction are the symmetrical dispiro-1,2,4-trithiolane 20 and the dispiro-1,4,2-dithiazolidine 21 (Scheme 6). The structure of the latter was established by X-ray crystallography. A reaction mechanism involving an intermediate thiocarbonyl-S-sulfide and a thiocarbonyl-S-imide is proposed in Scheme 2.