Palladium-catalyzed Reactions For The Synthesis Of Diarylalkynes And Phenanthrenes

Phenanthrenes are one of the most simple and stable fused aromatics among polycyclic aromatic hydrocarbons?PAHs?.They have attracted much attention because of their extraordinary physical properties,bioactivities and electronic properties.In particular,with the development of organic semiconductive materials during the last four decades,phenanthrene is qualified as a highly attractive building block for conjugated systems owing to its high resonance energy and high energy gap.Tremendous scientific effort has been devoted to their potential applications in the field of organic electronics such as organic field-effect transistors?OFETs?,OLED emitter materials,and so on.Therefore,the efficient synthesis of phenanthrene derivatives has been the focus of chemists.The rapid development of transition metal-catalyzed coupling reactions has made it possible to construct phenanthrene derivatives,and the most widely study is the construction of phenanthrene compounds by transition metal-catalyzed alkyne insertion.In this paper,the application ofPhenanthrenes in the field of optoelectronic materials and the basic theory of palladium catalysis are discussed.A series of explorations and studies on the synthesis of acetylene and the construction of phenanthrene derivatives are carried out.Based on the above research background,we have completed the following two aspects of work:1.It ws successfully achieved with the cheap and readily available bromobenzene and acetylenic alcohol as substrates,Pd?OAc?₂ as catalyst and Ph₂PtBu as ligand,by palladium-catalyzed Sonogashira coupling reaction.This method had good substrate compatibility and obtained the target compound in high yield.And we could also obtain higher separation yields when the reaction was amplified.2.An efficient palladium-catalyzed three-component cascade reaction has been developed for the facile construction of phenanthrene frameworks.The transformation is driven by a controlled reaction sequence of Suzuki–Miyaura coupling followed by the insertion of alkynes,and finally,annulation to yield phenanthrene derivatives via C–H activation.This methodology is able to accommodate a variety of substrates and affords the anticipated products in good to excellent yields.Though the formation of regioisomers is unavoidable due to 1,4-palladium migration for the substrates of 4-substituted o-bromoiodobenzenes,this onepot,multistep reaction is still an appealing strategy and might find application in the synthesis of polycyclic aromatic hydrocarbons?PAHs?because of its straightforward,practical and step economy.