The Application Of Sulfur Participation In Heterocyclic Reactions

Because of the stronger nucleophilicity of sulfur than oxygen, sulfur is easy to form Sulfonium ion and propargyl sulfide compounds are prone to joint-ene rearrangement. Therefore, sulfur participation is an important means for building heterocyclic compounds in organic synthesis. In recent years, there are a lot of heterocyclic compounds synthesized with the sulfur participation.In this paper, we investigated the synthesis of a series of oxazole derivatives and benzo [c] thiophene derivatives using sulfur participation.First, phenylthio propyne was used as the main starting material to synthesize a series of N-(1-(phenyl sulfinyl)-2-yl-4-yl)-acetamides. And then in the presence of trifluoroacetic anhydride, with the Pummerer rearrangement of the acetamides in anhydrous dichloromethane and the temperature slowly risen from-78℃to room temperature, the corresponding 5-(2-(phenylthio)vinyl-1,3-oxazoles were obtained. These oxazole compounds can be found in many bioactive compounds and used as synthetic intermediates.Secondly, alkenyl propargyl sulfide compounds were used as starting materials to synthesize 4,5-dihydro-benzo [c] thiophenes in anhydrous toluene. In the presence of the mild base DBU, alkenyl propargyl sulfide compounds were converted efficiently to 4,5-dihydro-benzo [c]thiophenes in good yields. Because of the importance of thiophene-based compounds in many areas including material, medicinal and synthetic chemistry, benzo[c]thiophenes are also considered an important class.