74576-66-2Relevant academic research and scientific papers
Rates and mechanisms of oxidative addition to zerovalent palladium complexes generated in situ from mixtures of Pd0(dba)2 and triphenylphosphine
Amatore, Christian,Jutand, Anny,Khalil, Fouad,M'Barki, Mohamed A.,Mottier, Lo?c
, p. 3168 - 3178 (1993)
The composition of mixtures of Pd0(dba)2 (dba = dibenzylideneacetone) and triphenylphosphine was examined in THF and DMF, as well as their reactivity vis à vis oxidative addition of PhI. It is concluded that, at equilibrium, these catalytic systems contain lesser available amounts of the species active in oxidative addition, viz. the low-ligated zerovalent palladium intermediate Pd0(PPh3)4 , than Pd0(PPh3)4 solutions do for an identical concentration of zerovalent palladium. This arises because, in contradiction with usual assumptions, dba is a better ligand than triphenylphosphine, for the low-ligated active Pd0(PPh3)2 , as evidenced by the small values (0.14) of the equilibrium constants of Pd0(dba)(PPh3)2 + PPh3 + solvent ? solvent-Pd0(PPh3)3 + dba in THF or DMF. As a result, oxidative addition of PhI to mixtures of Pd0(dba)2 and 2 equiv of triphenylphosphine proceeds at an overall rate that is ca. 10 times less than that to Pd0(PPh3)4. However, it is shown that oxidative addition to the two systems proceeds via the same transient intermediate, the solvated low-ligated Pd0(PPh3)2 ' moiety, evidencing that coordination by dba is not involved in the transition state of oxidative addition. This validates a posteriori previous assumptions on such transition states made in the literature, particularly for rationalization of enantiomeric selectivity when chiral phosphines are used.
Synthesis of new styrylarenes via Suzuki-Miyaura coupling catalysed by highly active, well-defined palladium catalysts
Kostera, Sylwia,Kownacki, Ireneusz,Kubicki, Maciej,Majchrzak, Mariusz
, p. 15535 - 15539 (2015/11/25)
An efficient synthetic route for well-defined palladium(0) complexes [Pd(η2-dba)(PPh3)2] (2), [Pd(η2-dba)(PCy3)2] (3) and their crystallographic structures is reported. This is the first crystallographic characterization of palladium complexes coordinated with one dibenzylideneacetone and two phosphines. A highly effective, fully controlled method for selective synthesis of mono- (5-9) and distyrylarenes (10-15) via Suzuki-Miyaura coupling is described. ? The Royal Society of Chemistry 2013.
Palladium-catalyzed coupling reactions of tetrafluoroethylene with arylzinc compounds
Ohashi, Masato,Kambara, Tadashi,Hatanaka, Tsubasa,Saijo, Hiroki,Doi, Ryohei,Ogoshi, Sensuke
, p. 3256 - 3259 (2011/04/24)
Organofluorine compounds are widely used in all aspects of the chemical industry. Although tetrafluoroethylene (TFE) is an example of an economical bulk organofluorine feedstock, the use of TFE is mostly limited to the production of poly(tetrafluoroethylene) and copolymers with other alkenes. Furthermore, no catalytic transformation of TFE that involves carbon-fluorine bond activation has been reported to date. We herein report the first example of a palladium-catalyzed coupling reaction of TFE with arylzinc reagents in the presence of lithium iodide, giving α,β,β-trifluorostyrene derivatives in excellent yields.
Regioselectivity in the Sonogashira coupling of 4,6-dichloro-2-pyrone
Fairlamb, Ian J. S.,O'Brien, Ciara T.,Lin, Zhenyang,Lam, King Chung
, p. 1213 - 1216 (2007/10/03)
The Sonogashira cross-coupling of 4,6-dichloro-2-pyrone with terminal acetylenes proceeds in good yields and high regioselectivity for the 6-position; dibenzylidene acetone (dba) type ligands play a non-innocent role in reactions mediated by Pd(dba)2/PPh3; theoretical studies indicate that C-6 oxidative addition is favoured both kinetically and thermodynamically.
Unexpected bell-shaped effect of the ligand on the rate of the oxidative addition to palladium(0) complexes generated in situ from mixtures of Pd(dba)2 and para-substituted triarylphosphines
Amatore, Christian,Jutand, Anny,Meyer, Gilbert
, p. 76 - 84 (2008/10/08)
As with PPh3, mixtures of Pd(dba)2 and n L (L = para-Z-substituted triphenylphosphines, n ≥ 2) in DMF lead to the formation of Pd(dba)L2 and PdL3 in equilibrium with PdL2. The equilibrium between Pd(dba)L2 and PdL3 is more in favor of PdL3 when the phosphine is less electron rich. In other words, the exchange of the dba ligand by a phosphine from Pd(dba)L2 to form PdL3 is more favored when the phosphine is less electron rich. The less ligated complex PdL2 is the reactive species in the oxidative addition with phenyl iodide. It was therefore expected that the rate of the oxidative addition would increase when the phosphine is more electron rich. However, surprisingly, when the palladium(0) complex is generated from mixtures of Pd(dba)2 and n L (n ≥ 2), the oxidative addition does not follow a linear Hammett correlation and the reactivity of the palladium(0) complex exhibits a maximum value. This is due to two antagonist effects. Indeed, the overall reactivity in the oxidative addition is governed by two factors: the intrinsic reactivity of PdL2 and its concentration. When the phosphine becomes more electron rich, the complex PdL2 becomes more nucleophilic and its intrinsic reactivity in the oxidative addition increases. However, when the phosphine becomes more electron rich, the concentration of PdL2 decreases because the equilibrium between the palladium(0) complexes becomes more in favor of Pd(dba)L2. These results emphasize the crucial role of the dba ligand on the reactivity of palladium(0) complexes generated in situ in mixtures of Pd(dba)2 and phosphines.
