Synthesis Of Dibenzothiophenes From 2-Arylphenylthiols Under PdCl₂/DMSO Catalysis

Due to its superior performance,organic functional molecules containing dibenzothiophene skeletons have been widely used in materials such as organic field-effect transistors,organic light emitting diodes,and organic solar cells.Conventional methods for synthesizing dibenzothiophenes generally require multi-steps from halides and active organometallic reagents,and suffered from availability of starting materials,tedious procedure,and low yields.Therefore,it is particularly important to develop a simple and efficient synthetic method for dibenzothiophenes.In this thesis,readily available 2-arylphenylthiols were used as starting materials for the efficient synthesis of dibenzothiophene derivatives under palladium/DMSO catalysis.The method features mild conditions,wide substrate compatibility,and good yield.Importantly,this method allows multifold reaction which enables the synthesis of largep-conjugated organic functional materials.The dissertation includes the following four parts:PartⅠ:We reviewed the progress of sulfur-containing organic functional materials,and described our research plan and strategy.PartⅡ:We synthesized a series of o-aminobiphenyl compounds from commercial aryl boronic acid and aryl halides by Suzuki coupling reaction.The o-aminobiphenyl compounds underwent diazotization,Sandmeyer reaction and hydrolysis leading to a series of substituted2-arylphenylthiols.Part Ⅲ:firstly,we have an introduction about the reported synthetic methods of dibenzothiophene compounds.We hypothesized that dibenzothiophene derivatives can be synthesized via cyclization of 2-arylphenythiols under transitional-metal catalysis.Next,we optimized the reaction conditions.After extensive conditions optimization,we found the best conditions through which various substituted dibenzothiophenes can be synthesized in high yields under the catalysis of PdCl₂/DMSO system.The reaction has the following advantages:（1）simple catalytic system,and PdCl₂ as the sole metal catalyst;（2）no additives such as ligands,oxidants,and bases;（3）DMSO as an oxidant,ligand,and solvent;（4）wide substrate scope;（5）allowing multifold cyclization.Importantly,this methodology demonstrated synthetic utilities in the construction of strained compounds of significant synthetic challenge,such as an organic semiconductor DBTDT and a buckybowl trithiasumanene.Part Ⅳ:We designed some control experiments and isolated the possible intermediates for the reaction.Based on the experiment,we proposed a plausible mechanism for this palladium catalyzed cyclization of 2-arylphenylthiols.