Study On Synthesis Of Two Sulfur-Containing Heterocyclic Compounds By Deoxygenation Of Lawesson’s Reagent

Sulfur-containing heterocyclic compounds widely exist in nature and play an important role in the fields of life science,medicinal chemistry and material science.Especially in the research area of medicinal chemistry,the introduction of sulfur-containing heterocycles gives compounds some unique biological activities.At present,great progress has been made in the construction of heterocyclic skeleton containing sulfur.However,most of the existing synthesis methods have the disadvantages of multi-step reaction,the use of expensive metal catalysts,the difficulty of substrate preparation and purification.Therefore,it is very important to develop a simple,efficient and green method for the synthesis of sulfur-containing heterocyclic compounds.In view of the existing problems in the construction of sulfur-containing heterocyclic skeleton,during the postgraduate period,I carried out the following work using Lawesson’s reagent as the sulfur source:1.Lawesson’s Reagent Promoted Deoxygenation of Anhydrides for the Syntheses of 3-Substituted or 3,4-Disubstituted ThiophenesUsing cheap Na HCO₃ as base catalyst and succinic anhydride as substrate,the synthesis of 3-or 3,4-disubstituted thiophene compounds was obtained by directly recurring to the thiolation and deoxygenation of Lawesson’s reagent.The method has the advantages of wide application range of substrates,good functional group compatibility and moderate yield.It is worth mentioning that dicarbonyl oxazolidone compounds cannot react under this condition,but mono-carbonyl oxazolidone can achieve the conversion to thiazole.The proposed synthesis strategy provides a new choice for simple and efficient synthesis of polysubstituted thiophene compounds.2.Lawesson’s Reagent Promoted Deoxygenation of Azlactones for the Syntheses of 2,4-Disubstituted ThiazolesOn the basis of the work of 1,2,4-disubstituted thiazoles have been synthesized directly by using azlactones as substrate through the deoxygenation of Lawesson’s reagent without metal or external additives.The method has wide application range,good functional group compatibility and the highest yield of 92%.Further,the importance of this methodology was also justified by a gram-scale synthesis.The proposed method is not only a further extension of the deoxygenation of Lawesson’s reagent,but also provides a new idea for the synthesis of other heterocyclic rings（such as isoxazole,imidazole and pyrazole）.