RT info:eu-repo/semantics/article
T1 Experimental Study of the Mechanism of the Pd-catalyzed Aryl-alkyl Negishi Coupling using Hybrid Phosphine- Electron Withdrawing Olefin Ligands
A1 Gioria, Estefanía
A1 Martínez de Ilarduya Martínez de Ilarduya, Jesús María
A1 Espinet Rubio, Pablo
K1 Chemistry
AB A detailed study of the Negishi cross-coupling reaction of ArI (Ar = 2-C6H4CO2Et) and ZnEt2 with palladium catalysts containing conventional phosphines versus one using a chelating hybrid phosphine–electron-withdrawing olefin (P-EWO) ligand reveals that for conventional phosphines (e.g., PPh3) β-H elimination from intermediate [PdArEt(PPh3)2] is competitive with Ar–Et reductive elimination and is responsible for part of the undesired reduction product ArH. In contrast, with the EWO phosphine, the β-H elimination from intermediate [PdArEt(P-EWO)] is slow compared to the fast Ar–Et reductive elimination, and the undesired reduction product ArH observed proceeds in this case of hydrolysis of ZnArEt, formed in transmetalations where Ar is transferred from Pd to Zn. The rate of these transmetalations is comparable to the rate of reductive eliminations. Consequently, undesired transmetalations affording [PdEt2(P-EWO)] and ZnArEt are more effective at early stages of the reactions and less effective when the ethylating agent becomes poorer in ZnEt2 and richer in ZnEtX (X = I), as the reaction proceeds. Careful analysis of the experiments reveals the detailed changing evolution of the reaction, not only providing the main features of the catalytic cycle but also deducing how the reagents in the system change with time and what the effects on the products of these changes are.
PB American Chemical Society
SN 0276-7333
YR 2014
FD 2014
LK http://uvadoc.uva.es/handle/10324/21730
UL http://uvadoc.uva.es/handle/10324/21730
LA eng
NO Organometallics, 2014, 33 (17), p. 4394–4400
NO Producción Científica
DS UVaDOC
RD 22-nov-2024