| The couplings of aryl halides are powerful tools for the formation of C—C bond. In this thesis, we investigated the symmetrical and unsymmetrical coupling and Heck coupling reactions of aryl halides, and the results are summarized below.(1) The direct coupling of aryl halides for the preparation of symmetrical and unsymmetrical biaryls were performed successfully in poly(ethylene glycol) (PEG) using Pd(OAc)2 as catalyst in the absence of other additives and reductants. The selectivity toward biaryl was found to depend on the amount of PEG used. Excessive PEG decreased the hydrodehalogenation product. When the concentration of the hydroxyl group in PEG achieves 100 mol% relative to aryl halides, the best selectivity was obtained. The catalyst system could be recycled for reuse up to five times without obvious deactivation.(2) A PEG-supported ionic liquid ([PEGmim][Cl]) was synthesized and applied to Pd-catalyzed Heck coupling reaction as a novel reaction media. Using the Pd(OAc)2-[PEGmim][Cl] system, the Heck reaction of both aryl bromides and activated aryl chlorides with olefins could afford the coupling products in excellent yields. Furthermore, the Pd(OAc)2-[PEGmim][Cl] catalytic system could be recycled five times without obvious deactivation. |
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