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Title: Experimental Study of the Mechanism of the Pd-catalyzed Aryl-alkyl Negishi Coupling using Hybrid Phosphine- Electron Withdrawing Olefin Ligands
Authors: Gioria, Estefanía
Martínez de Ilarduya, Jesús María
Espinet Rubio, Pablo
Issue Date: 2014
Publisher: American Chemical Society
Description: Producción Científica
Citation: Organometallics, 2014, 33 (17), p. 4394–4400
Abstract: 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.
Keywords: Chemistry
ISSN: 0276-7333
Peer Review: SI
DOI: 10.1021/om5005379
Sponsor: Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. GR169 and VA256U13)
Ministerio de Economía, Industria y Competitividad (CTQ2013-48406-P)
Language: eng
Rights: info:eu-repo/semantics/openAccess
Appears in Collections:CINQUIMA - Artículos de revista
DEP63 - Artículos de revista

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