Palladium-catalyzed cross-coupling reaction of aryl(trialkyl)silanes with aryl nitriles

Small Phosphine Ligands Enable Selective Oxidative Addition of Ar-O over Ar-Cl Bonds at Nickel(0)

Current methods for Suzuki-Miyaura couplings of nontriflate phenol derivatives are limited by their intolerance of halides including aryl chlorides. This is because Ni(0) and Pd(0) often undergo oxidative addition of organohalides at a similar or faster rate than most Ar-O bonds. DFT and stoichiometric oxidative addition studies demonstrate that small phosphines, in particular PMe3, are unique in promoting preferential reaction of Ni(0) with aryl tosylates and other C-O bonds in the presence of aryl chlorides. This selectivity was exploited in the first Ni-catalyzed C-O-selective Suzuki-Miyaura coupling of chlorinated phenol derivatives where the oxygen-containing leaving group is not a fluorinated sulfonate such as triflate. Computational studies suggest that the origin of divergent selectivity between PMe3 and other phosphines differs from prior examples of ligand-controlled chemodivergent cross-couplings. PMe3 effects selective reaction at tosylate due to both electronic and steric factors. A close interaction between nickel and a sulfonyl oxygen of tosylate during oxidative addition is critical to the observed selectivity.

The design, synthesis and validation of recoverable and readily reusable siloxane transfer agents for Pd-catalyzed cross-coupling reactions

The development of competent, recoverable and reusable 1-oxa-2-silacyclopentene (siloxane) transfer agents for Pd-catalyzed cross-coupling reactions (CCRs) of organolithium reagents with aryl and alkenyl iodides has been achieved. Drawbacks of the first-generation siloxane-transfer agent (1), relating to facile recovery for potential recycling, have been addressed.

Synthesis, characterization and microwave-promoted catalytic activity of novel N-phenylbenzimidazolium salts in Heck-Mizoroki and Suzuki-Miyaura cross-coupling reactions under mild conditions

A number of novel benzimidazolium salts having aryl substituents such as N-phenyl, 4-chlorophenyl and various alkyl substituents were synthesized. Their microwave-assisted catalytic activities were evaluated in Heck-Mizoroki and Suzuki-Miyaura cross-coupling reactions using a catalytic system consisting of Pd(OAc)₂/K₂CO₃ in DMF/H₂O under mild reaction conditions with consistent high yields, except those of 2-bromopyridine.