Investigation On The Construction And Functionalization Of Aromatic Sulfur Heterocyclic Compounds

Aromatic thioheterocyclic compounds are widely found in natural products,medicines,pesticides,and functional materials,and have wide application prospects.Since sulfur atoms are easily coordinated with metals to poison metals,the development of metal-free catalyzed methods,green efficient construction of such important compounds,and new reactions to achieve C-S bond activation through appropriate catalytic systems have been hot topics in organic synthesis.This dissertation focuses on the synthesis of 3-thiocoumarin and3-thioquinolinone derivatives using iodine catalysis and the C-S bond activation of 3-thio electron-rich heterocycles olefins under palladium/copper system,and the following results were achieved.?1?A new method for the electrophilic cyclization of arylsulfinic acid sodium with phenyl propiolate or acetylene amide has been developed to efficiently construct 3-aromatic thiol coumarins and quinolinone derivatives.The method uses iodine as a catalyst,PCy₃ as a reducing agent,and DMSO as an oxidant,through the role of iodine and reducing agent to the sodium sulfonate into disulfide,which in turn generate electrophilic aromatic sulfur iodine reagent?ArSI?to attack alkyne undergoes electrophilic cyclization,eventually lose protons to get the target product.This method is free from the participation of metals.The sulfur source is inexpensive,stable,safe,and low in toxicity.The functional groups are tolerant and the substrate has a wide range of applications.Preliminary mechanistic studies have shown that the electrophilic arylthioiodide ArSI is the key intermediate in the reaction.?2?The cross-coupling reaction of 3-hydrocarbylthioindole and pyridoimidazole derivatives with phenylboronic acid was developed under the condition that Pd?PPh₃?₄ was the catalyst and CuTC was the promoter.The resulting alkenyl palladium intermediate undergoes palladium-sulfur bond polarization under the promotion of copper ions.The coordination of the oxygen of the anion-activated carboxylate in the copper salt with the boron atom to form a six-membered intermediate is the key to the success of the reaction.This method has good functional group compatibility,which could achieve good conversion of both N-protected and N-H indoles,thus showing the potential of building complex molecules in organic synthesis and medicinal chemistry.This dissertation focuses on the construction and functionalization reaction of aromatic sulfur heterocyclic compounds and extends the construction of aromatic sulfur-based heterocyclic compounds without metal catalyst and the functionalization reaction of palladium/copper systems.Meanwhile,provided a new method and new technology for the efficient synthesis and conversion of aromatic sulfur heterocyclic compounds with different structures,which enriches the connotation of organic synthetic chemistry and green chemistry.The research has certain theoretical significance and application value.