The Synthesis Of Diarylfluorene Via Palladium-catalyzed Csp~2-Csp~3Cross-coupling And The Application Of Diarylfluorene

Palladium-catalyzed cross-coupling reactions have always been the most effectivetrategies for the construction of C-C bonds, such as Suzuki coupling, Sonagashira coupling, Heckreaction which have been broadly utilized for the synthesis of materials and pharmaceuticals. In thefield of organic optoelectronics, highly efficient preparation of organic semiconductors has been animportant research area, and the palladium-catalyzed C-C couplings are certainly the most popularsynthetic strategies. This thesis accomplished palladium-catalyzed Csp3-Csp2couplings tosynthesize various kinds of diarylfluorenes by utilizing mono-aryl substituted fluorene or fluoreneas the substrates. Compared with traditional synthetic methods, this method is more effective andalso has broader substrate applicability. More importantly, a series of diarylfluorenes which couldnot be prepared by traditional methods have also been successfully synthesized. Research work ofthis thesis focuses on four aspects as follows:1. By employing the palladium-catalyzed Csp3-Csp2coupling in the presence ofmono-arylfluorene, we achieved the efficient construction of quaternary carbon-centers, along withthe synthesis of diarylfluorenes which have important application as photoelectric materials. Bytesting various reaction parameters, we obtained the best reaction condition：5mol%of [Pd(dba)2],10mol%of PPh3,1.2equiv of aryl bromide,1.2equiv of KOtBu in toluene at100oC for8–10hours. Furthersubstrate scope was tested, confirming the good universality of this synthetic protocol. Under thestandard conditions, a series of diarylfluorenes with electron-rich substituents were smoothlyobtained in good yields. Notably, more challenging produrcts such as electron-deficientdiarylfluorenes and meta-substituted diarylfluorenes were also resoundingly synthesized.2. Based on the research results of last chapter, by employing fluorene as the substrate, wesynthesized diarylfluorenes in one step. The results indicated that this method is also highlyefficient and with good substrate tolerance. Compared with the traditional methods,palladium-catalyzed cross-couplings can be utilized for the synthesis of more challengingdiarylfluorenes which could not be synthesized by previous methods, such as fluorine or chlorinesubstituted diarylfluorenesor meta-substituted diarylfluorenes. Meanwhile, to further clarify therelationship between diarylfluorenes synthesis from mono-arylfluorenes and diarylfluorenessynthesis from simple fluorene, preliminary investigations of reaction process was conducted.3. Encouraged by previous work, a series of diarylfluorenes with spiro rings at the core were designed and synthesized by palladium-catalyzed Csp3-Csp2couplings. Structures of all thesecompounds were confirmed by NMR and HRMS spectra analysis.Furthermore, photoelectricalproperties of these compounds were preliminary investigated by UV-Vis and fluorescence spectraanalysis. Among these compounds, some are host materials and some are potential undopedphosphorescent materials.4. To take advantage of the methodological research results, we tried to extend small moleculecoupling reaction for polymerization. We screened different reaction conditions, such as Pd, ligand,temperature, of small molecular prototype reaction, and preliminarily explore the feasibility of thisreaction for the synthesis of diarylfluorene polymer materials and further research goals.