A study of the behaviour of 2,4substituted thiosemicarbazides toward orthoesters: Formation of mesoionic compounds

The reactions beetwen 2,4disubstituted thiosemicarbazides and orthoesters in refluxing xylene led to the formation of the 1,2,4triazoline5thione ring and to the 1,2,4triazolium5thiolate ring. The formation of the mesoionic componds is due to rearrangement of the easily available 2,4disubstituted thiosemicarbazides to 1,4disubstituted thiosemicarbazides under the reaction conditions adopted. This method can be usefully used for the synthesis of mesoionic compounds, especially in the case of the 2methyl4phenylthiosemicarbazide.