Novel Nitrogen-Containing Aromatics Via Palladium-Catalyzed Intramolecular Arylation

Palladium-catalyzed coupling reaction is one of the most efficient synthetic strategies in modern organic synthesis, which could be divided into palladium-catalyzed intermolecular and intramolecular couplings. The advantages of this synthetic methodology are high yield, quicker reaction rate, therefore it is suitable choice for synthesis of polycyclic aromatic hydrocarbons (PAHs). In recent years, the subjects of C-H bond activation by palladium-catalysts has become a fast developing while fully challenging area within organometallic chemistry, which could be used as synthetic strategy in drug chemistry, biology, agriculture and material sciences. This thesis focused on the synthesis of three kinds of fluorine-based compounds:diindeno-carbazoles, fluoradene and spirobifluorenes by the means of palladium-catalyzed intramolecular arylation. Meanwhile, we have studied their optical spectroscopy, crystal structures and thermal stabilities.In the first part, we synthesized the diindenocarbazoles. Starting with 2,7-dibromo-9-hexylcarbazole, the Friedel-Crafts acylation reaction was employed to afford 3,6-dibenzoyl-2,7-dibromo-N-hexylcarbazole. The direct intramoleular arylation of this intermediate through C-H bond activation were not successful by various of palladium catalyst systems. It was reduced by using of Wolf-Kishner-Huang reduction to 3,6-dibenzyl-2,7-dibromo-N-hexylcarbazole, then the ring cluosure was completed by double C-H activation catalyzed by palladium catalyst. Prelimary investigation of the final products indicated that they have good luminescent properties.In the second part, previously unknown and highly strained 7b-arylfluoradenes were intensively synthesized for the first time. The key step for synthetic strategy is to employ palladium-catalyzed intramolecular arylation through aromatic C-H bond activation. Fluoradenes, namely indeno[1,2,3-jk]fluorine, the two subunits, indeno-and fluorine co-share a bridge-head carbon center, therefore it is hard to approach through conventional synthetic methodologies. We employed 9-(2-bromophenyl) fluoren-9-ol as the key intermediate to react with different nitrogen-containing compounds such as carbazole, N-hexylcarbazole, triphenylamine as well as N,N',N"-trihexyltriindole to afford bromide intermediates by acid-promoted Friedel-Crafts reactions, followed by using of catalyst system such as Pd(OAc)2 /PPh3/Na2CO3/DMA/BnEt3NBr to complete ring closure step according to the proton abstraction mechanism. The optical spectroscopy, crystal structures and thermal stabilities were also studied. They might be suitable components in material science.In the third part, we synthesized three dispirobifluorenes via palladium-catalyzed intramolecular arylation as the key step. By combination of results described above, well-defined synthetic routes to approach target molecules were designed. The key intermediates such as 3,6-bis(9-phenyl-9-fluorenyl)-2,7-dibromo-carbazole and 2,5-bis(9-phenyl-9-fluorenyl)-1,4-dibromobenzene were obtained through metal-halogen exchange and acid-promoted Friedel-Crafts reaction, while palladium-catalyzed intramolecular coupling played a key role to finalize the targets. Preliminary investigations indicated that they have strong luminescent properties.