New Insights into Xantphos/Pd-Catalyzed C−N Bond Forming Reactions: A Structural and Kinetic Study

Autor:	and Timothy E. Barder, Liane M. Klingensmith, Stephen L. Buchwald, Eric R. Strieter
Rok vydání:	2005
Předmět:	Xantphos Organic Chemistry Kinetic energy Medicinal chemistry Dissociation (chemistry) Catalysis Inorganic Chemistry Reaction rate chemistry.chemical_compound chemistry Reaction calorimeter Morpholine Organic chemistry Physical and Theoretical Chemistry Equilibrium constant
Zdroj:	Organometallics. 25:82-91
ISSN:	1520-6041 0276-7333
Popis:	Both (Xantphos)Pd(dba) and Pd(Xantphos)2 were identified in mixtures of Pd2(dba)3 and Xantphos by use of 31P NMR and independent syntheses. At high ligand concentrations, Pd(Xantphos)2 was found to be the predominant species. Reaction calorimetry was employed to determine whether the formation of Pd(Xantphos)2 affects the rate at which the Pd-catalyzed C−N bond formation occurs between 4-tert-butylbromobenzene and morpholine. Indeed, the concentration of Xantphos dramatically influences the activity of the catalyst, with high concentrations of Xantphos inhibiting the reaction rate due to the formation of Pd(Xantphos)2. Two plausible hypotheses for the low activity of Pd(Xantphos)2 as a precatalyst are (1) a slow rate of Xantphos dissociation from Pd(Xantphos)2 inhibits the formation of an active (Xantphos)Pd0 species and (2) the high degree of insolubility of Pd(Xantphos)2 results in the precipitation of a significant fraction of the precatalyst from the reaction mixture. Although the equilibrium constant...
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::56e99fb4e434360268c303f4776d9f40 https://doi.org/10.1021/om050715g Zobrazit plný text záznamu