On Ying Yuen
Published: 2016
Total Pages: 563
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In the second half of dissertation, two studies with regard to traditional cross-coupling reactions of aryl chlorides with organometallic reagents are carried out. Firstly, palladium-catalyzed Hiyama cross-coupling reaction of aryl and heteroaryl chlorides with aryl and heteroaryltrialkoxysilanes under solvent-free reaction condition is presented. The catalyst system comprising of Pd(OAc)2́2 and PCy2́2-Andolephos (Chapter 6, L2) is a highly effective for this coupling reaction with low catalyst loading (down to 0.05 mol% Pd) and short reaction time (3 h). A broad substrate scope containing electron-rich, -neutral, and -deficient and sterically hindered aryl chlorides is achieved. Notably, the first general examples of Hiyama cross-coupling reaction using heteroaryltrialkoxysilanes are demonstrated. The presence of acetic acid or water suppresses the decomposition of aryl chlorides and promotes the product yields. A large scale experiment without degasification and purification of reactants is also conducted smoothly. Last but not least, a general palladium-catalyzed borylation of aryl chlorides with pinacol borane is reported. A newly modified indolylphosphine ligand (Chapter 7, L18) is prepared via an efficient protocol involving Fischer indolization from readily available phenylhydrazine and 2'-hydroxyacetophenone. The combination of Pd(dba)2́2 and newly modified indolylphosphine ligand (Chapter 7, L18) are shown to be an effective catalyst for the borylation of non-activated and activated aryl chlorides with pinacol borane. Addition of tetra-n-butylammoniumiodide (TBAI) is highly effective for coupling of aryl chlorides bearing function groups such as keto, nitile and ester. 1 mol% Pd catalyst loading can be achieved using this catalytic system.