Suzuki aqueous

The Suzuki reaction97 allows tire coupling of two aromatic rings by reaction of an arylboronic compound with a iodo or bromo aryl derivative. The tetrakis (U iphenylphosphine) Pd is the catalyst working in the basic medium. This reaction was recently used98 in aqueous media for the preparation of different isomers of diphenyldicarboxylic acids (Fig. 5.21) but also for the synthesis of soluble rodlike polyimides99 by coupling the 3,6-diphenyl- V, V,-bis(4-bromo-... 

The first example of microwave-promoted solid-phase methodology in heterocyclic chemistry was the arylation of thiophene and indole via Suzuki couplings on TentaGel S RAM resin, as demonstrated by Hallberg and coworkers in 1996, before temperature- and pressure-controlled microwave instruments were even available [189]. Three years later Schotten and coworkers presented analogous but aqueous Suzuki couplings of 5-bromo-thiophene anchored to PEG soluble support via a carboxylic function at its C-2 position [116]. Unfortunately, this work was performed in a do-... 

Alternatively, 3-phenyl pyrazinone was prepared via Suzuki reaction, when a polymer-bound pyrazinone was irradiated with 4 equiv of phenylboronic acid, 5 equiv of Na2C03 and 20 mol % of Pd[P(Ph)3]4 as the catalyst in DMF as the solvent (Scheme 36). Contrary to the results obtained in solution phase [29], all attempts to drive the reaction toward the formation of disub-stituted compound, using higher equivalents of reagents or longer reaction times, were unsuccessful. Apphcation of aqueous conditions afforded mixtures of 3-mono and 3,5-disubstituted pyrazinones. 

Swanson MB, WA Ivancic, AM Saxena, JD Allton, GKO Brian, T Suzuki, H Nishizawa, M Nokata (1995) Direct photolysis of fenpyroximate in a buffered aqueous solution. J Agric Food Chem 43 513-518. 

Sterically demanding, water-soluble alkylphosphines 6.10 and 6.11 as ligands have been found to have a high activity for the Suzuki coupling of aryl bromides in aqueous solvents (Eq. 6.35).115 Turnover numbers up to 734,000 mmol/mmol Pd have been achieved under such conditions. Glucosamine-based phosphines were found to be efficient ligands for Suzuki cross-coupling reactions in water.116... 

Organoboron compounds cannot react without proper activation. The use of oxygen bases is inherent in the standard Suzuki-Miyaura cross-coupling method. Fluorides (usually CsF) can be used as alternative activating agents, which is particularly useful in cases when the reagents are incompatible with oxygen bases for the reactions run under anhydrous conditions,24 (66) 241 Fluoride activation can be effective, however, even under aqueous phase-transfer conditions (67) 242... 

Anionic complexes of boron (boronates, borinates, etc.) have been introduced as convenient reagents in cross-coupling reactions of broad scope, particularly interesting for the transfer of alkynyl and primary alkyl residues, which cannot be accomplished using the standard protocols of the Suzuki-Miyaura reaction. Readily available Ph4BNa can be used as a convenient reagent for phenylation in place of the much more expensive PhB(OH)2, and all four phenyl groups can be utilized when the reaction is carried out with a phosphine-free catalyst in aqueous solutions.244... 

Citterio D., Omagari M., Kawada T., Sasaki S., Suzuki Y., Suzuki K., Chromogenic betaine lariates for highly selective calcium ion sensing in aqueous environment, Anal. Chim. Acta 2004 504 (2) 227-234. 

Several microwave-assisted protocols for soluble polymer-supported syntheses have been described. Among the first examples of so-called liquid-phase synthesis were aqueous Suzuki couplings. Schotten and coworkers presented the use of polyethylene glycol (PEG)-bound aryl halides and sulfonates in these palladium-catalyzed cross-couplings [70]. The authors demonstrated that no additional phase-transfer catalyst (PTC) is needed when the PEG-bound electrophiles are coupled with appropriate aryl boronic acids. The polymer-bound substrates were coupled with 1.2 equivalents of the boronic acids in water under short-term microwave irradiation in sealed vessels in a domestic microwave oven (Scheme 7.62). Work-up involved precipitation of the polymer-bound biaryl from a suitable organic solvent with diethyl ether. Water and insoluble impurities need to be removed prior to precipitation in order to achieve high recoveries of the products. 

The group of Ley has reported on the use of palladium-doped perovskites as recyclable and reusable catalysts for Suzuki couplings [151]. Microwave-mediated cross-couplings of phenylboronic acid with aryl halides were achieved within 1 h by utilizing the supported catalyst (0.25 mol% palladium) in aqueous 2-propanol (Scheme 7.127). The addition of water was crucial as attempted transformations in non-aqueous mixtures did not proceed. 

Scheme 12.16 Microwave-assisted aqueous Suzuki couplings with PEG-bound aryl halides or sulfonates.

Kobayakawa, K., Miura, T., Suzuki, A., Sato, Y., and Fujishima, A., Enhancement of the photocatalytic activity of CdS powder for hydrogen evolution from aqueous sulfide solution by heat treatment with KC1, Solar Energ. Mater. Solar Cells, 30, 201,1993. 

Today, the Suzuki cross coupling of aryl halides and arylboronic acids is also carried out in aqueous-biphasic operation starting from chlorinated derivatives instead of their more costly bromo or iodo equivalents (Equation 5.6, [39]). 

J. Terao, A. Tang, J.J. Michels, A. Krivokapic, and H.L. Anderson, Synthesis of poly(p-phenylene vinylene) rotaxanes by aqueous Suzuki coupling, Chem. Commun. 56-57, 2004. 

Greater durability of the colloidal Pd/C catalysts was also observed in this case. The catalytic activity was found to have declined much less than a conventionally manufactured Pd/C catalyst after recycling both catalysts 25 times under similar conditions. Obviously, the lipophilic (Oct)4NCl surfactant layer prevents the colloid particles from coagulating and being poisoned in the alkaline aqueous reaction medium. Shape-selective hydrocarbon oxidation catalysts have been described, where active Pt colloid particles are present exclusively in the pores of ultramicroscopic tungsten heteropoly compounds [162], Phosphine-free Suzuki and Heck reactions involving iodo-, bromo-or activated chloroatoms were performed catalytically with ammonium salt- or poly(vinylpyrroli-done)-stabilized palladium or palladium nickel colloids (Equation 3.9) [162, 163],... 

The Suzuki coupling of 2-iodo-2-cyclohexen-1-one and 4-methoxy-phenylboronic acid is achieved using silver(l) oxide as a suspension in aqueous THF as the base. Unlike earlier reports,15-17 in which up to 6 equiv of Ag2mild conditions, rapid conversion can be achieved at room temperature for a large variety of sensitively functionalized partners in near quantitative yields (see Table).18... 

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