Palladium-catalyzed C-H Activation/Cyclization Of Alkynes Towards The Synthesis Of Polycyclic Aromatic Hydrocarbons

With the development of modern information display technology,organic optoelectronic materials have attracted more and more attention in recent years.Among them,the commercial application of these materials lies on the superior material properties and low cost.Therefore the synthesis and properties study both play important roles in the development of organic optoelectronic materials.According to the structural study,the common characteristic of organic optoelectronic materials might be large ?-conjugate system to achieve the purpose of electronic flow.Thus,polycyclic aromatic hydrocarbons(PAHs)represent the preferred structure for most organic optoelectronic materials due to not only the rigid planar structure to achieve the larger ?-conjugated system,but also the huge space for the regulation of material properties.The synthetic methods for PAHs are various,such as the Friedel–Crafts reaction,transition metal catalyzed cross-coupling and so on.However,to the best of knowledge,transition metal catalyzed cross-coupling is the most adopted method because of good functional group compatibility,high synthesis efficiency and atomic economy.Of course,it still remains an outstanding challenge to achieve flexible,effective and simple synthesis methods for the synthesis of organic optoelectronic materials.In this paper,a briefing were given first about the application of PAHs in organic optoelectronic materials and the research background of transition metal catalyzed cross-coupling,and then the cyclization of alkynes catalyzed by transition metal to synthesize PAHs in recent years was reviewed.Our research focused on the synthesis of naphthalene and fluorene derivations which were described as following:1.Pd(OAc)2/PCy3 catalyzed intramolecular cyclization of o-bromodiphenylmethane for the synthesis of fluorene and its derivations.Based on the previous work in our group,we disclosed another approach for the synthesis of fluorene and its derivations via activation of aryl C-H bond..I The reactions occurred smoothly and allowed both electron-rich and electron-deficient substrates converted to the corresponding fluorenes in good to excellent yields.Studies revealed that this Pd-catalyzed cyclization was also available for the substrates of 2'-chloro-diarylmethanes.This approach could afford the diversity in fluorene-based molecular architectures such as 3,6-substituted fluorene derivatives which was difficult to be synthesized by conventional methods and therefore would provide more opportunity on research of the properties of material molecules.particularly2.Pd(OAc)2/ t-Bu3 P catalyzed intermolecular cyclization of alkynes for the synthesis of naphthalene and its derivations.This new cascade reaction provided an efficient way for the construction of naphthalene compounds by employing simple and easy-available substrates of bromoarene and diarylacetylene.Comparing with similar synthetic method,the remarkable difference lies in the avoidance of the addition of expensive silver salts.This three-component reaction proceeded smoothly in moderate to excellent yields with good functional-group compatibility which would certainly attract the attention of organic chemists interested in this class of compounds.