Suzuki coupling palladium/carbon

The Suzuki-Miyaura synthesis is one of the most commonly used methods for the formation of carbon-to-carbon bonds [7]. As a palladium catalyst typically tetrakis(triphenylphosphine)palladium(0) has been used, giving yields of44—78%. Recently, Suzuki coupling between aryl halides and phenylboronic acid with efficient catalysis by palladacycles was reported to give yields of 83%. 

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-... 

Equation 5.2. describes a transformation, where the palladium catalysed Suzuki coupling was used to establish the first carbon-carbon bond between an indole ring and an acetophenone moiety en route to benzo[c]carbazole. The carbacycle was established in a potassium er -butoxide mediated photochemical transformation.2... 

The bromo derivative of A -mcthylsuccinimide did also undergo Suzuki coupling when treated with naphthylboronic acid in the presence of palladium acetate, triphenylphosphine and potassium carbonate (6.3.). The coupled product was deprotected under the reaction conditions and an indole derivative was isolated in good yield, which was successfully converted into the hexacyclic naphthopyrrolo[3,4-c]carbazole structure. Using the analogous trimethylstannyl-naphthalene derivative and optimised Stille coupling conditions the desired product was isolated only in 56% yield.5... 

The Suzuki coupling of aryl halides was also extended to tosylates recently. Benzothiazole 5-tosylate reacted with m-xylene-2-boronic acid (6.13.) to give the coupled product in 94% yield using palladium acetate and a stericly congested biphenyl based phosphine ligand as catalyst.17 Another class of less commonly utilised cross-coupling partners are methyltio derivatives. In the presence of a copper salt, which activates the carbon-sulphur bond, 2-methyltio-benzotiazol coupled readily with a series of arylboronic acids.18... 

Since the Suzuki coupling of purine derivatives was covered by recent reviews,1 we only present a selection lfom these reactions. Xanthine (3,6-dihydropurine-2,6-dione) derivatives were coupled with different boronic acids, including styrylboronic acid, in the presence of the conventional tetrakis(triphenylphosphino)palladium catalyst and tripotassium phosphate as a mild base (8.1.), to obtain the appropriate 8-substituted xanthines in acceptable yield.4 The advantage of the use of anhydrous tripotassium phosphate as base over the classical aqueous carbonate or hydroxide reagents might be attributed to the sensitivity of the 8-halopurine core towards nucleophilic attack. 

An improved procedure of Suzuki-couplings was recently described by Buchwald [5] et al. By using 0-(di-tert.butyl-phosphino)-biphenyl as ligand, palladium acetate and potassium carbonate couplings are facilitated at room temperature [eq. (c)]. 

A modification of the Suzuki coupling reaction proved to be a clean and useful method for the preparation of monosubstituted arylferrocenes. Iodoferrocene was reacted with a series of substituted arylboronic acids in the presence of sodium carbonate and palladium acetate in aqueous ethanol at room temperature to produce a range of substituted monoarylfer-rocenes (Eq. (19)). A systematic investigation undertaken to determine the optimal reaction conditions indicated that scrupulous deoxygenation of the solvent is critical. The use of... 

As mentioned above, palladium-catalyzed couplings of fluoroalkenes are becoming part of the repertoire of organofluorine chemists. However, the range of fluoroalkenes that have been coupled is still very limited and a ubiquitous feature is the presence of a (small) fluorine atom at the a-carbon. Recently, Percy et al. have reported that 1-(N,N-diethylcarbamoyloxy)-2,2-difluoro-l-iodoethene undergoes smooth Suzuki coupling (Eq. (79)) [122]. 

Synthesis of the anti-inflammatory drug flurbiprofen by an environmentally efficient Suzuki coupling that uses water as the solvent and palladium on carbon as a reusable catalyst. 

Various carbon-carbon cross-coupling reactions are employed to arrive at oligomers from fluorene monomers, including nickel-cataylzed Yamamoto coupling between aryl halides [48], palladium(0)-catalyzed Suzuki coupling between boronic acids/esters and halides [49], and ferric-chloride-catalyzed Scholl reaction, also called Friedel-Crafts arylation, of bare fluorenes [50,51]. 

The Sonogashira coupling of 2,4-dichloroquinoline in water with a palladium-carbon catalyst (triphenylphosphine, triethylamine, Cul, 80 °C) shows complete selectivity for the 2-position and Suzuki couplings of 1,3-dichloroisoquinoline are selective for C-1. ... 

Palladium-catalysed carbonylation of halides, with carbon monoxide, can be used to prepare esters, amides and ketones by trapping the intermediate acylpalladium halide with alcohols,amines and organometal-lics, respectively. Boronic acids are probably the best organometallics for the preparation of ketones, but conditions must be adjusted to give the best selectivity between the acylation reaction and simple Suzuki coupling of the boronic acid with the starting halide. ... 

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