The immobilized N-heterocyclic carbene-Pd complex was readily prepared by reaction of silica gel-supported imidazolium chloride with Pd(OAc) 2 . The Pd complex exhibited excellent catalytic activity in the coupling reaction of aryl halides with arylboronic acid. The heterogeneous Pd catalyst was reusable as well as air-stable to allow easy use.
Chiral amino thioacetate ligands were prepared from the corresponding amino alcohols and used as catalysts for enantioselective aryl transfer reaction. The amino thioacetates were remarkably superior to the corresponding amino alcohols. Low catalyst loadings of only 1-2.5 mol % were sufficient to achieve excellent enantioselectivity as well as high conversion in short reaction time. The results reveal that the thioacetoxy moiety of the amino thioacetates has a surprisingly beneficial effect in enhancing the asymmetric induction.
Palladium acetate was encapsulated onto highly ordered mesoporous silica MCM-41 with the aid of ionic liquid. The immobilized Pd complex can efficiently catalyze Heck coupling reactions of activated and non-activated aryl halides with acrylates. The Pd catalyst exhibited remarkably high catalytic activity and outstanding stability. Moreover, the immobilized palladium acetate could be recycled at least six times without significant loss of activity.
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