304435-67-4Relevant academic research and scientific papers
Soluble polymer-supported hindered phosphine ligands for palladium-catalyzed aryl amination
Khamatnurova, Tatyana V.,Zhang, Dongmei,Suriboot, Jakkrit,Bazzi, Hassan S.,Bergbreiter, David E.
, p. 2378 - 2383 (2015)
Strategies for synthesis of more effective soluble supported ligands for phosphine-ligated Pd(0) cross coupling catalysts have been explored. Reversible addition-fragmentation chain transfer (RAFT) polymerization has been used to prepare alkane-soluble poly(4-alkylstyrene)-bound phosphine ligands. 4-tert-Butylstyrene and 4-dodecylstyrene were copolymerized with ca. 7 mol% of 4-chloromethylstyrene or a 4-diphenylphosphinestyrene monomer using RAFT chemistry to afford poly(tert-butylstyrene-co-4-dodecylstyrene) copolymers. Polymers with chloromethyl groups were allowed to react with the phenolic group of a hindered dicyclohexylbiarylphosphine ligand. This hindered polymer-bound phosphine formed reactive Pd complexes useful in haloarene amine couplings. All aryl halide amination reactions had Pd leaching that was typically 0.1% of the charged Pd with one example having only 0.02% Pd leaching. These Pd complexes of poly(4-alkylstyrene)-bound phosphines were also compared to similar hindered phosphine complexes formed with a polyisobutylene (PIB), whose terminus was also converted into a dicyclohexylbiarylphosphine ligand. Palladium catalysts ligated by these hindered biarylphosphines on poly(4-alkylstyrene) and PIB-bound both were recyclable in the absence of oxygen, had similar activity, and very low Pd leaching. This journal is
Homogeneous Catalysts Supported on Soluble Polymers: Biphasic Suzuki-Miyaura Coupling of Aryl Chlorides Using Phase-Tagged Palladium-Phosphine Catalysts
An Der Heiden, Markus,Plenio, Herbert
, p. 1789 - 1797 (2007/10/03)
The Suzuki-Miyaura coupling of aryl chlorides and PhB(OH)2 under biphasic conditions (DMSO/heptane) can be performed in almost quantitative yields over several cycles by means of polymeric Pd catalysts with soluble polyethylene glycol phase tags. Three sterically demanding and electron-rich phosphines 1-CH2Br,4-CH2P(1-Ad) 2-C6H4, and 2-PCy2,2′ -OH-biphenyl, and 2-PtBu2,2′-OH-biphenyl were covalently bonded to 2000 Dalton MeOPEG-OH. The catalysts, which were formed in situ from Na2[PdCl4], the respective polymeric phosphine, KF/K 3PO4, and PhB(OH)2, efficiently couple aryl chlorides at 80°C at 0.5 mol% loading, resulting in a > 90% yield of the respective biphenyl derivatives. The use of polar phase tags allows the efficient recovery of palladium-phosphine catalysts by simple phase separation of the catalyst-containing DMSO solution and the product-containing n-heptane phase. The high activity (TOF) of the catalyst remains almost constant over more than five reaction cycles, which involve the catalytic reaction, separation of the product phase from the catalyst phase, and addition of new reactants to initiate the next cycle. The Buchwald type biphenyl phosphines form the most active Pd catalysts, which are 1.3-2.8 times more active than catalysts derived from diadamantyl-benzylphosphine, but appear to be less robust in the recycling experiments. There is no apparent leaching of the catalyst into the heptane solution ( 0.05%), as evidenced by spectrophotometric measurements, and contamination of the product with Pd is avoided.
Use of polymer-supported dialkylphosphinobiphenyl ligands for palladium-catalyzed amination and Suzuki reactions
Parrish,Buchwald
, p. 3820 - 3827 (2007/10/03)
The preparations of polymer-supported dialkylphosphinobiphenyl ligands (3) are reported. A palladium catalyst based on ligand 3a is active for amination and Suzuki reactions using unactivated aryl iodides, bromides, or chlorides. Filtration of the catalyst from the reaction mixtures allows for simplified product isolation via an aqueous workup. The resin-bound catalyst can be recycled without additional palladium in both the amination and Suzuki reactions.
