The Synthesis Of Benzoxaborole Derivatives Via Palladium-catalyzed Cross-coupling And The Application Of Benzoxaborole Derivatives

Since benzoxaboroles were first synthesized and characterized as early as in 1957 by Torssel, they were largely neglected in the past fifty years and have begun to draw interests from researchers in recent years. Benzoxaboroles were widely used in organic synthesis, catalysis, glycopeptides recognition, supramolecular chemistry, biology, medicine and material science due to their unique chemical properties in comparison to their acyclic boronic acid counterparts. At the same time, various methods have been developed for the construction of this five-membered ring system. However, most of the current approaches suffer from i) limited substrate scope or the lack of readily available precursors, and ii) tedious synthetic procedures, which prohibit them from application in organic electrons. In order to prepare benzoxaboroles in easier, cheaper and more flexible strategy, we creatively accomplishes palladium-catalyzed Cross-Coupling to synthesize various kinds of Benzoxaborole Derivatives that utilizing o-bromobenzylic alcohols compounds and B2pin2 as starting materials, which are cheap and available. Research work of this thesis focuses on three aspects as follows:Firstly, we synthesize a series of o-bromobenzylic alcohols containing primary alcohols, secondary alcohols, tertiary alcohols and acyclic tert-alcohols based on the work centre of our group.In addition, Under very mild conditions, functionalized benzoxaborole derivatives were prepared in good to excellent yields via a palladium-catalyzed Miyaura borylation reaction of readily available unprotected o-bromobenzylalcohols, and bis(pinacolato)diboron(B2pin2). Compared with traditional synthetic methods, this method is more effective and also has broader substrate applicability. By testing various reaction parameters, we obtained the best reaction condition: 1.0 equiv o-bromobenzylalcohols, 1.5 equiv B2pin2, 3.0 equiv KOAc, 10 mol% Pd(PPh3)2Cl2 in DMSO at 90 oC for 16 h. Further substrates scope was tested, confirming the good universality of this synthetic protocol and solving the difficulty which the literature ie reported to have difficulty in functionalization at 3-position. Futhermore, we can not only synthesize a series of benzoxaborole derivatives obtained by traditional synthetic methods, but also synthesize one class of boron-containing spirocyclic aromatic compounds.At last, we have designed and systhesized the pyrene-substituted spirofluorenes-based organic semiconductors, which will become important monomers for blue-light emitting materials. Photoelectrical properties of these compounds were preliminary investigated by UV-Vis, fluorescence spectra, Time-resolved fluorescence and Cyclic voltammetric analysis. We find it is potential undoped luminescent materials in OLEDs that they will become in the coming future.