Suzuki with phenyl boronic acid

Gagn6 et al. developed polymer active sites that additionally contained a receptor (recognition sites) displayed in the outer sphere of the metal center (reactive site). The Suzuki reaction of /)-bromoanisole with phenyl boronic acid and the allylation of dimethyl malonate with allyl acetate were both chosen to assess the presence and/or effect of the crown-ether in crown-ether-molecular imprinting polymer-palladium complex. The results showed that molecular imprinting can be used to functionalize the second-coordination sphere of a transition metal complex and subsequently affect its catalytic behavior. 

Scheme 1.28 Palladium-catalyzed arylation with phenyl boronic acid (71) (Suzuki, 1981).

Coordinatively, unsaturated [(l,6-diene)PdL] (L = phosphine) complexes are also efficient catalysts for the Suzuki-Miyaura coupHng of aryl chlorides with phenyl-boronic acid [125, 126]. 

Various palladium(O) monophosphine complexes of 1,6-diene have been prepared from tmedaPd(CHj)2, PRj, and the corresponding 1,6-dienes. These molecularly defined Pd complexes catalyzed the Suzuki coupling of aryl chlorides with phenyl-boronic acid more efficiently than traditional Pd(Il)-PRj pre-catalysts. Best results were achieved with the 1,6-diene complex containing Buchwald s ligand (26). With only 0.05 mol% of the catalyst, good to excellent yields of biaryls were obtained from activated (2-chlorobenzonitrile, 97%), non-activated (4-chlorotoluene, 82%, chlorobenzene, 87%) and deactivated (4-chloroanisole, 72%) aryl chlorides (Equation 54) [66]. 

Water-soluble calix[n]arenes are powerful receptors for non-polar substrates in aqueous solution. These compounds are promising candidates as carrier molecules for the transport of non-polar substrates through bulk water as well as inverse phase-transfer catalysts, as proven for the Suzuki coupling of iodobenzene with phenyl boronic acid [91]. 1.5-bis(4,4 -bis(perfluorooctyl)penta-l,4-dien-3-one (39) stabilizes palladium 0) nanoparticles (transmission electron microscopy) formed in the reduction of palladium dichloride with methanol. These palladium colloids are soluble in perfluorinated solvents, and they are efficient recoverable catalysts for Suzuki crosscoupling under fluorous biphasic conditions (Equation 69) [92]. 

In another study, Gallon et al. used polyaniline (PANI) nanofiber-supported palladium nanoparticles as catalysts for the coupling of aryl chlorides with phenyl boronic acid in water [98]. Typically, the aryl chlorides were ineffective in most Suzuki coupling reactions but, by subshtuhng the aryl halide appropriately, it could be shown that Pd nanoparticles were capable of carrying out the transforma-hon in the aqueous phase. 

Ternary Pd-catalyzed coupling reactions of bicyclic olefins (most often norbor-nadiene is used) with aryl and vinyl halides and various nucleophiles have been investigated intensively over the past few years [44]. A new approach in this field is to combine Heck and Suzuki reactions using a mixture of phenyliodide, phenyl-boronic acid and the norbornadiene dicarboxylate. Optimizing the conditions led to 84% of the desired biphenylnorbornene dicarboxylate [45]. Substituted phenyl-iodides and phenylboronic acids can also be used, though the variation at the norbornadiene moiety is highly limited. 

In a more recent study, Wang and coworkers have discussed microwave-assisted Suzuki couplings employing a reusable polymer-supported palladium complex [141]. The supported catalyst was prepared from commercial Merrifield polystyrene resin under ultrasound Bonification. In a typical procedure for biaryl synthesis, 1 mmol of the requisite aryl bromide together with 1.1 equivalents of the phenyl-boronic acid, 2.5 equivalents of potassium carbonate, and 10 mg of the polystyrene-... 

The first microwave-promoted Suzuki couplings were reported in 1996 (Eq. 11.20) [17]. Phenyl boronic acid was coupled with 4-bromotoluene to give a fair yield of product after a reaction time of less than 3 min under single-mode irradiation. The same reaction had previously been conducted with a reported reaction time of 4 h. 

Equation 11.20 Suzuki coupling of phenyl boronic acid with 4-bromotoluene. 

Application of the complexes 63 in the Mizoroki-Heck reaction did not reveal higher activity than the previously examined palladium(II) complexes. However, in the Suzuki-Miyaura reaction, a drastically increased activity was observed with complex 63. Catalysis starts without a measurable induction period at mild temperatures accompanied by an extraordinarily high turnover frequency (TOF) of 552 [mol product x mol Pd x h ] at the start of the reaction for the coupling of p-chlorotoluene and phenyl boronic acid [Eq. (48)]. ... 

Tschierske developed a variety of molecules containing a p-terphenyl unit as backbone equipped with two terminal decyloxy chains and laterally attached crown ethers of different sizes [51-53]. The synthesis was straightforward starting from methyl-2,5-dibromobenzoate 30 that was coupled with [4-(decyloxy)phenyl]boronic acid 31 in a subsequent Pd°-catalyzed Suzuki reaction. The 2-hydroxymethyl crown ethers 32 were attached in the last step (Scheme 18) to yield mesogenic 33. 

The first microwave-promoted Suzuki couplings were published in 1996 (Scheme 44). Phenyl boronic acid was coupled with 4-methylphenyl bromide... 

Our group recently reported the development of a coumarin library with diversity at the 6-position via Suzuki-Miyaura coupling.21 The reaction conditions were optimized for the reaction of the 6-bromocoumarin scaffold 9 with the unsubstituted phenyl boronic acid pinacol ester 10a (Figs. 18.6 and 18.7). 

The utility of this process was further demonstrated when the one-pot Suzuki coupling procedure was demonstrated to produce 188 in excellent yield [96]. Procedurally, after the first coupling had occurred, phenyl boronic acid was added along with additional Pd(PPh3)4. 

Suzuki-Miyaura coupling can be conducted under electro-osmotic flow (EOF) conditions, In this case, the Pd catalyst is immobilized in the channel (Figure 8.16). The injection of 4-bromobenzonitrile for 5 s with a 25 s injection interval into a continuous stream of phenyl boronic acid gives 4-cyanobiphenyl in 67% yield. 

The air-stable phosphine-borane la was evaluated in the Pd-catalyzed Suzuki-Miyaura reaction. Typically, 4-bromoanisole and phenyl boronic acid were efficiently coupled using 1 mol% of PdCOAc) and 2 mol% of ligand la (Scheme 6). The BMes moiety is compatible with the cross-coupling and it actually improves catalytic activity (under the same conditions, PPh gives a notably lower yield). Interestingly, a catalytically competent Pd(0) complex 39 was isolated and fully characterized. The phosphine-borane adopts a new coordination mode besides phosphorus, the Pd center is coordinated by one of the Mes groups at B interaction). 

Suzuki coupling of 4-chIoroacetophenone 1 mol% of each catalyst (Pd) was mixed with 1.0 ml of IM 4-chloroacetophenone in toluene, phenyl boronic acid (182 mg or 1.5 mmol) and 3mmol of base (174 mg potassium fluoride or 637 mg... 

Suzuki coupling of 4-bromoanisole 1 mol% of catalyst (Pd) was mixed with 2.5 mg of IM 4-bromoanisole in solvent, phenyl boronic acid (455 mg or 3.75 mmol) and 7.5 mmol of potassium carbonate base (1045 mg). The reaction mixtures were stirred and heated under argon to 60 C or to 100 C or the boiling point of the solvent if less than 100 C (methanol 65 C, ethanol 78"C, acetonitrile 82 C, THF 65 C). Sanqiles were withdrawn and analysed as in the previous experiment. 

They suggested that the size and shape of the Au NPs are crucial to enhance the catalytic activity of the Suzuki-Miyaura coupling reaction of phenyl boronic acid and chlorobenzene. According to their report, flower-shaped Au NPs possess higher catalytic activity than the spherical Au NPs due to its smaller size of about 4 run and uniform distribution of particles. Also the yield of the desired product increases with increase in the concentration of the catalyst which clearly proves that Au NPs decorated on GO has excellent catalytic activity towards Suzuki-Miyaura coupling reaction of phenyl boronic acid and chlorobenzene. 

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