Bimetallic Cooperativity with a 2-Phosphinoimidazole-Derived Pd(II) Dimer Enables Naphthalene Synthesis via dimeric Pd(III) Catalysis
semanticscholar(2020)
摘要
We report the synthesis of bimetallic Pd(I) and Pd(II) complexes scaffolded on bidentate 2-phosphinoimidazole
ligands. These complexes display unique catalytic activity and enable the expeditious formation of 1,3-disubstituted naphthalenes via an unprecedented coupling of
aryl iodides and methyl ketones in the presence of silver triflate. Excellent substrate
scope for naphthalene formation is also demonstrated. Mechanistic studies suggest
that the transformation proceeds via Pd-catalyzed arylation of a methyl ketone, followed by cyclization with a second equivalent of ketone. Importantly, this ketone
arylation processes occurs under oxidizing conditions, suggesting involvement of
higher oxidation state dimeric Pd catalysts. Based on experiments and DFT calculations, we propose a mechanism involving high oxidation state Pd(III) bimetallic catalysis. These new bimetallic complexes
possess reactivity that is not seen with monometallic Pd catalysts and we confirm the importance of the palladium catalyst
for both arylation and cyclization for naphthalene formation.
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