| Poly-substituted thiophenes are widely used in many fields such as pesticides,medicines,materials,etc.Thiophenes are also important building blocks in the synthesis of highly complex natural products.S3·-species has been known for many years and can be very easily formed by the reaction of some sulfur reagents with alkalai in electron pair donor solvents at room temperature.However,applications for the synthesis of organosulfur compounds involving S3·-are very rare.In this thesis,we mainly study S3·-in situ generated from S3·-mediated cyclization reactions with different radical acceptors for the synthesis of thiophene derivatives via C-S bond formations.This study also expands the application of S3·-in organic reactions.The whole work is constituted by three parts as follow:In the first part,S3·-in situ generated from K2S mediated[1+2+2]cycloaddition reaction with diaryl acetylenes is studied to construct tetraphenylthiophene derivatives.We synthesized a series of new tetra-aryl substituted thiophenes,which expanded the diversity of thiophene derivatives.This protocol provides a new,environment-friendly and simple strategy to construct tetra-aryl substituted thiophenes.In the second part,we study S3·-in situ generated from Na2S·9H2O mediated[1+3+1]cycloaddition reaction with cyelopropyl acetylenes to synthesize 2-benzylidenetetrahydrothiophenes.This protocol provides a new,simple and straightforward strategy to construct tetrahydrothiophene derivatives under transition metal-free conditions.We also find that Na2S·9H2O in DMF,DMA or DMSO could also in situ generate S3·-based on a electron spin-resonance(ESR)experiment.In the third part,we have developed S3·-mediated cyclization reactions of 1,3-enynes to give 2,3,5-trisubstituted thiophenes and 3-thienyl disulfides via two or six C-S bond formations It provides a good example for the study of C-S bonds construction reaction without transition metal catalysis. |
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