Iminothiolactone-thiolactam rearrangement in the synthesis of 4-amino-6-thioxo-3,7,9-triazatricyclo-[6.2.1.0 1,5 ]undec-4-ene-2,10-diones

The reaction of 4-amino-8-hydroxy-1,6-dioxo-2,7-diazaspiro[4.4]non-3-ene-4-carbonitriles with Lawesson's reagent proceeded as an iminothiolactone-thiolactam rearrangement, leading to the formation of 4-amino-6-thioxo-3,7,9-triazatricyclo[6.2.1.01,5]undec-4-ene-2,10-diones.