85100-62-5Relevant articles and documents
Scalable Negishi Coupling between Organozinc Compounds and (Hetero)Aryl Bromides under Aerobic Conditions when using Bulk Water or Deep Eutectic Solvents with no Additional Ligands
Dilauro, Giuseppe,Azzollini, Claudia S.,Vitale, Paola,Salomone, Antonio,Perna, Filippo M.,Capriati, Vito
supporting information, p. 10632 - 10636 (2021/04/09)
Pd-catalyzed Negishi cross-coupling reactions between organozinc compounds and (hetero)aryl bromides have been reported when using bulk water as the reaction medium in the presence of NaCl or the biodegradable choline chloride/urea eutectic mixture. Both C(sp3)-C(sp2) and C(sp2)-C(sp2) couplings have been found to proceed smoothly, with high chemoselectivity, under mild conditions (room temperature or 60 °C) in air, and in competition with protonolysis. Additional benefits include very short reaction times (20 s), good to excellent yields (up to 98 %), wide substrate scope, and the tolerance of a variety of functional groups. The proposed novel protocol is scalable, and the practicability of the method is further highlighted by an easy recycling of both the catalyst and the eutectic mixture or water.
Single-Electron-Transfer-Induced Coupling of Alkylzinc Reagents with Aryl Iodides
Okura, Keisho,Shirakawa, Eiji
supporting information, p. 3043 - 3046 (2016/07/14)
Alkylzinc reagents prepared from an alkyllithium and zinc iodide were found to undergo coupling with aryl and alkenyl iodides in the presence of LiI in a mixed solvent consisting of THF and diglyme (1:1). Alkyllithiums, prepared by halogen–lithium exchange between an alkyl iodide and tert-butyllithium, are also converted to alkylarenes through alkylzinc reagents.
Catalyst activation, deactivation, and degradation in palladium-mediated negishi cross-coupling reactions
B?ck, Katharina,Feil, Julia E.,Karaghiosoff, Konstantin,Koszinowski, Konrad
supporting information, p. 5548 - 5560 (2015/03/30)
Pd-mediated Negishi cross-coupling reactions were studied by a combination of kinetic measurements, electrospray-ionization (ESI) mass spectrometry, 31P NMR and UV/Vis spectroscopy. The kinetic measurements point to a rate-determining oxidative addition. Surprisingly, this step seems to involve not only the Pd catalyst and the aryl halide substrate, but also the organozinc reagent. In this context, the ESI-mass spectrometric observation of heterobimetallic Pd-Zn complexes [L2PdZnR]+ (L=S-PHOS, R=Bu, Ph, Bn) is particularly revealing. The inferred presence of these and related neutral complexes with a direct Pd-Zn interaction in solution explains how the organozinc reagent can modulate the reactivity of the Pd catalyst. Previous theoretical calculations by Gonzlez-Prez et al. (Organometallics 2012, 31, 2053) suggest that the complexation by the organozinc reagent lowers the activity of the Pd catalyst. Presumably, a similar effect also causes the rate decrease observed upon addition of ZnBr2. In contrast, added LiBr apparently counteracts the formation of Pd-Zn complexes and restores the high activity of the Pd catalyst. At longer reaction times, deactivation processes due to degradation of the S-PHOS ligand and aggregation of the Pd catalyst come into play, thus further contributing to the appreciable complexity of the title reaction. Catalytic complexity: The Pd catalyst used in Negishi cross-coupling reactions shows an unexpected heterogeneity and complexity. Among the various species observed in solution, heterobimetallic Pd-Zn complexes are of particular interest (see figure). These species also seem key to understanding the kinetics of Negishi cross-coupling reactions. S-PHOS=2-dicyclohexylphosphino-2,6-dimethoxybiphenyl.
