Zinc chloride-promoted aryl bromide-alkyne cross-coupling reactions at room temperature
(Chemical Equation Presented) Substoichiometric amounts of ZnCl2 promote the room temperature, Pd/P(t-Bu)3-catalyzed cross-coupling of aryl bromides with alkynes. Pd(I) dimer 1 is demonstrated to be a particularly active precatalyst for this reaction. The reaction is general for a wide variety of aryl bromides.
Finke, Aaron D.,Elleby, Eric C.,Boyd, Michael J.,Weissman, Haim,Moore, Jeffrey S.
Rapid Room-Temperature, Chemoselective Csp2?Csp2Coupling of Poly(pseudo)halogenated Arenes Enabled by Palladium(I) Catalysis in Air
While chemoselectivities in Pd0-catalyzed coupling reactions are frequently non-intuitive and a result of a complex interplay of ligand/catalyst, substrate, and reaction conditions, we herein report a general method based on PdIthat allows for an a priori predictable chemoselective Csp2?C Csp2coupling at C?Br in preference to C?OTf and C?Cl bonds, regardless of the electronic or steric bias of the substrate. The C?C bond formations are extremely rapid (Idimer under open-flask conditions.
Ligand- and Solvent-Tuned Chemoselective Carbonylation of Bromoaryl Triflates
The palladium-catalyzed chemoselective carbonylation of bromoaryl triflates is reported. The selective C?Br bond versus C?OTf (OTf=triflate) bond functionalization can be remarkably tuned by the combination of the ligand [4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos) vs. 1,1′-bis(diphenylphosphino)ferrocene (DPPF)] and the solvent (toluene vs. DMSO). The respective ligand and solvent effects are rationalized by DFT calculations. In contrast, the monodentate ligands BuPAd2 and tBu3P prefer the selective C?Br bond activation and are solvent insensitive.
Aryl bromide/triflate selectivities reveal mechanistic divergence in palladium-catalysed couplings; the Suzuki-Miyaura anomaly
In palladium-catalysed cross-coupling reactions, the outcome of competition between aryl bromides and aryl triflates depends on the nucleophilic partner; Suzuki couplings with R-B generally follow a different pattern from other R-M species. The Royal Society of Chemistry.
Espino, Gustavo,Kurbangalieva, Almira,Brown, John M.
p. 1742 - 1744
(2008/02/04)
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