Study On 1,2,4-Thiadiazole And Thiophene Synthesis From Sulfur Powder As Sulfur Source

Sulfur-containing organic compounds can be used in pesticides,dyes,detergents and various polymer functional materials.In the past two or three decades,a large number of sulfur-containing organic drugs have been developed and utilized.Therefore,the organic sulfur compounds that are molecularly diverse and structurally complex through C-S bond formation reactions have always been one of the research hotspots in organic synthesis chemistry.Based on the direct functionalization of C-H bonds and organosulfur compounds to construct C-S bonds,people have received extensive attention and made great progress on the construction of C-S bonds which based on the direct functionalization of C-H bonds and organosulfur compounds.Compared to organic sulfur sources and other inorganic sulfur sources,Elemental sulfur is widely distributed in nature,more stable,no special smell and cheap.Therefore,the use of elemental sulfur as a sulfur source for the construction of organic sulfur compounds is a simpler and more convenient method.This paper bases on" 1,2,4-thiadiazole and thiophene construction",a series of studies on the construction of thiadiazole and thiophene derivatives were developed using elemental sulfur as a sulfur source.The details are as follows:1.Palladium-catalyzed 3-aryl-5-acyl-1,2,4-thiadiazoles formation from ketones,amidines and sulfur Powder.The reaction was performed with palladium chloride as a catalyst,dipotassium hydrogen phosphate as an alkali additive,and reacted at 130?in an argon atmosphere for 24 hours.Ketones acted as carbon source and acyl source in this transformation.This method affords an efficient approach for the rapid synthesis of 3-aryl-5-acyl-1,2,4-thiadiazoles from readily available starting materials.2.A new method for one-pot synthesis of 2,3,5-trisubstituted thiophenes by three components using phenylacetaldehyde,elemental sulfur and acetylacetone.In this reaction system,potassium carbonate and potassium bicarbonate are used as additives to synthesize 2,3,5-trisubstituted thiophene compounds under mild,transition metal-free conditions.By this method,we prepared a variety of 2,3,5-trisubstituted thiophene compounds with high yield and good functional group tolerance.