Design of a versatile and improved precatalyst scaffold for palladium-catalyzed cross-coupling: (η3-1-tBu-indenyl)2(μ-Cl)2Pd2
We describe the development of (η3-1-tBu-indenyl)2(μ-Cl)2Pd2, a versatile precatalyst scaffold for Pd-catalyzed cross-coupling. Our new system is more active than commercially available (η3-cinnamyl)2(μ-Cl)2Pd2 and is compatible with a range of NHC and phosphine ligands. Precatalysts of the type (η3-1-tBu-indenyl)Pd(Cl)(L) can either be isolated through the reaction of (η3-1-tBu-indenyl)2(μ-Cl)2Pd2 with the appropriate ligand or generated in situ, which offers advantages for ligand screening. We show that the (η3-1-tBu-indenyl)2(μ-Cl)2Pd2 scaffold generates highly active systems for a number of challenging cross-coupling reactions. The reason for the improved catalytic activity of systems generated from the (η3-1-tBu-indenyl)2(μ-Cl)2Pd2 scaffold compared to (η3-cinnamyl)2(μ-Cl)2Pd2 is that inactive PdI dimers are not formed during catalysis.
Melvin, Patrick R.,Nova, Ainara,Balcells, David,Dai, Wei,Hazari, Nilay,Hruszkewycz, Damian P.,Shah, Hemali P.,Tudge, Matthew T.
NOVEL PRECATALYST SCAFFOLDS FOR CROSS-COUPLING REACTIONS, AND METHODS OF MAKING AND USING SAME
The present invention provides novel transition-metal precatalysts that are useful in preparing active coupling catalysts. In certain embodiments, the precatalysts of the invention are air-stable and moisture-stable. The present invention further provides methods of making and using the precatalysts of the invention.
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Page/Page column 60; 61
(2016/05/02)
Design and preparation of new palladium precatalysts for C-C and C-N cross-coupling reactions
A series of easily prepared, phosphine-ligated palladium precatalysts based on the 2-aminobiphenyl scaffold have been prepared. The role of the precatalyst-associated labile halide (or pseudohalide) in the formation and stability of the palladacycle has been examined. It was found that replacing the chloride in the previous version of the precatalyst with a mesylate leads to a new class of precatalysts with improved solution stability and that are readily prepared from a wider range of phosphine ligands. The differences between the previous version of precatalyst and that reported here are explored. In addition, the reactivity of the latter is examined in a range of C-C and C-N bond forming reactions.
Bruno, Nicholas C.,Tudge, Matthew T.,Buchwald, Stephen L.
Described are palladium precatalysts, and methods of making and using them. The palladium precatalysts show improved stability and improved reactivity in comparison to previously-described palladium precatalysts.
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Paragraph 0056; 0298
(2014/01/08)
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