Studies On Syntheses Of Thioether And Isothiourea Via Benzyne Intermediate Generating From O-Diiodibenzene

This thesis includes two sections:The first section is the reaction of thiophenol and o-diiodobenzene to synthesize aryl thioether.Because of its high electrophilic activity,benzyne can quickly react with nucleophilic thiophenol to obtain thioether compounds.This C-S coupling mode does not require the participation of transition metals,which is in line with the modern synthetic concept of atomic economy and green environmental protection.The traditional metal-free C-S coupling reaction needs iodonium,sulfonium,benzyne precursor or other active species,which are difficult to prepare and require high cost.In this study,we found that under the action of sodium hydride,o-diiodibenzene can be used as a new type of aryne precursor to react with thiophenol to efficiently synthesize o-iodioaryl sulfide.The o-diiodibenzene starting materials are cheap and easy to obtain,and the reaction conditions are mild.More importaintly,o-iodoaryl thioether products can be widely transformed to a variety of 1,2-disubstituted benzene,which provides a simple and convenient way for the synthesis of complex natural products and drug molecules.The second section is about the study on the synthesis of S-arylisothioureas from thiourea and o-diiodobenzene.Isothiourea structure is an important synthetic building block,widely existing in some active natural products,chemical drugs and reaction catalysts.The syntheses of S-arylisothioureas are usually mediated by transition metals,which have some problems such as harsh conditions and metal catalyst contamination.Therefore,the direct S-arylation of thiourea using benzyne is the most economical,environmental friendly,efficient and direct method.In this research,we used o-diiodide benzene to produce benzyne under the action of sodium hydride,and then S-arylated with thiourea to form S-(2-iodoaryl)isothioureas.This method has the advantage of simple operation and a wide range of substrates,and the ortho-substituted diiodibenzene substrates have a high degree of regioselectivity.