A Purification-Free Method for the Synthesis of Thiazolium Salts Using P2S5-Py2 Complex or P4S10

An expedient method to prepare thiazolium salts using the P2S5-Py2 complex or P4S10 has been studied. A variety of thiazolium salts can be rapidly accessed by the clean reaction between readily available α-formamido ketones and these reagents. The pure thiazolium salts are obtained via simple filtration followed by salt metathesis with sodium tetrafluoroborate or sodium tetraphenylborate. The method is suitable for a variety of substituents on the heterocycle. The use of these reagents confers a practical advantage over the use of Lawesson’s reagent, making the purification of the thiazolium salt straightforward.