Room temperature reactions Suzuki-Miyaura coupling

Caztn and coworkers reported that easily prepared [(IPr)PdCl2] dimer 10 [14] and a series of mixed P(OR)3/NHC Pd complexes 11 [15] could be used in Suzuki-Miyaura coupling reactions at low catalyst loadings and at room temperature. For the latter, the authors carried out a series of experiments that suggested that alcohok or alkoxide groups play a major role in the activation of the complexes to generate the catalytically active Pd(0) species. 

Sawai K, Tatumi R, Nakahodo T, Fujihara H (2008) Asymmetric Suzuki-Miyaura coupling reactions catalyzed by chiral palladium nanoparticles at room temperature. Angew Chem Int Ed 47 6917-6919... 

Suzuki-Miyaura cross-coupling reaction (Scheme 6.24). Conversions of up to 90% (TON = 90,000) within 2 h were achieved in toluene under reflux [76]. The same group reported on Pd-complexes of the type 42 that form efficient room temperature catalytic systems for the Suzuki-Miyaura coupling of poorly reactive aryl-chlorides (Scheme 6.24) [77]. 

A similarly high performance has been reported for oxime-derived (125) and benzylsulfide-derived (126) palladacycles.438 These precatalysts are effective in the cross-coupling of arylboronic acids,438,439 organotin compounds,440 and terminal acetylenes441 with aryl iodides and bromides, and of activated aryl chlorides. SC-palladacycles can effect the Suzuki-Miyaura reaction even at room temperature. 

Additionally, Suzuki-Miyaura cross coupling reactions can be performed on similar supported iodides. Aryl bromides could be employed in this reaction as well. After optimization of conditions, it turned out that a hydroxyl-derived IL was the best solvent for this reaction. Namely, reaction completion was obtained after 12 h at room temperature in [N11130H][NTf2] in the presence of 1% Pd(OAc)2 and using potassium carbonate as abase. Under these conditions, less than 1% of homocoupling product is observed and easily eliminated by washing with diethyl ether prior to transesterification with methanol. Overall, biphenyls were isolated under analytically pure form in 90-95% yields [126],... 

Chem 663 46 2002] obtained high turnover numbers and turnover frequencies in Suzuki-Miyaura cross-coupling reactions at room temperature conditions with this catalyst. Botella Najera [J Org Chem 70 4360 2005] also studied this catalyst for Mirozoki-Heck couplings in aqueous A. iV-dimethylacetamide in air using N-methyldicyclohexylamine (see [7560-83-0]) as base with or without Bu4NBr. 

Arylation of a wide range of NH/OH/SH substrates by oxidative cross-coupling with boronic acids in the presence of catalytic cupric acetate and either triethyl-amine or pyridine at room temperature in air. The reaction works for amides, amines, anilines, azides, hydantoins, hydrazines, imides, imines, nitroso, pyrazi-nones, pyridones, purines, pyrimidines, sulfonamides, sulfinates, sulfoximines, ureas, alcohols, phenols, and thiols. It is also the mildest method for NIO-vinylation. The boronic acids can be replaced with siloxanes or starmanes. The mild condition of this reaction is an advantage over Buchwald-Hartwig s Pd-catalyzed cross-coupling. The Chan-Lam C-X bond cross-coupling reaction is complementary to Suzuki-Miyaura s C-C bond cross-coupling reaction. 

The three basic steps in the palladium-catalysed Suzuki-Miyaura reaction involve oxidative addition, transmetalation, and reductive elimination. A systematic study of the transmetalation step has found that the major process involves the reaction of a palladium hydroxo complex with boronic acid, path B in Scheme 3, rather than the reaction of a palladium halide complex with trihydroxyborate, path A. A kinetic study using electrochemical techniques of Suzuki—Miyaura reactions in DMF has also emphasized the important function of hydroxide ions. These ions favour reaction by forming the reactive palladium hydroxo complex and also by promoting reductive elimination. However, their role is a compromise as they disfavour reaction by forming of unreactive anionic trihydroxyborate. A method for coupling arylboronic acids with aryl sulfonates or halides has been developed using a nickel-naphthyl complex as a pre-catalyst. It works at room temperature in toluene solvent in the presence of water and potassium carbonate. ... 

In 2001, Fu s group [128] reported the application of Pd-triarylphosphane-ferrocene catalysts for the Suzuki-Miyaura reaction on aryl chloride substrates (Figure 1.40a). Activated aryl chlorides could be coupled at room temperature, while unactivated aryl chlorides, including sterically hindered and electron-rich substrates, at 70 °C. The triarylphosphane - which is air stable - was mixed with either Pd2(dba)j or Pd(OAc)2 with KjPO -HjO as base in toluene at room temperature, and very good yields were obtained. 

Keywords Allyl bromides, benzyl bromides, diborylmethane derivative, Pd-catalysts such as [Pd-PEPPSI-IPr] (l)/Pd[P(f-Bu)3l2 (2), aq. KOH, dioxane, room temperature, Suzuki-Miyaura cross-coupling (SMC) reaction, C-C bond formation, regio- and chemoseletivity, homoallylboronates, alkylboronates... 

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