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.