Suzuki coupling palladium chloride

A rapid MW-assisted palladium-catalyzed coupling of heteroaryl and aryl boronic acids with iodo- and bromo-substituted benzoic acids, anchored on TentaGel has been achieved [174]. An environmentally friendly Suzuki cross-coupling reaction has been developed that uses polyethylene glycol (PEG) as the reaction medium and palladium chloride as a catalyst [175]. A solventless Suzuki coupling has also been reported on palladium-doped alumina in the presence of potassium fluoride as a base [176], This approach has been extended to Sonogashira coupling reaction wherein terminal alkynes couple readily with aryl or alkenyl iodides on palladium-doped alumina in the presence of triphenylphosphine and cuprous iodide (Scheme 6.52) [177]. 

Recently, the groups of Fu and Buchwald have coupled aryl chlorides with arylboronic acids [34, 35]. The methodology may be amenable to large-scale synthesis because organic chlorides are less expensive and more readily available than other organic halides. Under conventional Suzuki conditions, chlorobenzene is virtually inert because of its reluctance to oxidatively add to Pd(0). However, in the presence of sterically hindered, electron-rich phosphine ligands [e.g., P(f-Bu)3 or tricyclohexylphosphine], enhanced reactivity is acquired presumably because the oxidative addition of an aryl chloride is more facile with a more electron-rich palladium complex. For... 

The palladium nanoparticle is prepared from the reaction of the stabilizer, 4,4 -bis(perfluorooctyl)dibenzylideneacetone with palladium(II) chloride. The average size of the nanoparticle varied according the ratio of PdCF to the stabilizer, but was typically around 4 or 5 nm. The initial yield observed in the Suzuki coupling reaction was 90%, but decreased to 78% after five consecutive runs. Fluorous boronates (alternative precursors in Suzuki reactions), have also been developed for use in fluorous biphasic processes [12], A generic structure of a fluorous boronate is shown in Figure 10.2. 

Palladium catalysts have been found which are effective in the Suzuki coupling reaction of arylboronic acids with aryl chlorides carrying electron-withdrawing groups.73 Biaryls may also be synthesized by cross-coupling of arylboronic acids with arenediazonium salts.74,75 There has been a report of the polymer-bound palladium-catalysed Suzuki coupling of aryl triflates with organoboron compounds.76 Arylbor-onates may themselves be synthesized by the palladium-catalysed reactions of... 

As Figure 16.7 reveals, an aryl iodide reacts more rapidly with an alkynylcopper compound than an aryl bromide. The palladium-catalyzed C,C coupling reactions, which will be discussed later in the present chapter, also proceed more rapidly with an aryl iodide than with an aryl bromide (example Suzuki coupling in Figure 16.22) or an aryl chloride (example Stille reaction in Figure 16.27). There are still some details that are not fully understood one is inclined to assume that in accordance with the Hammond postulate the weaker C-I bond (dissociation energy DE = 51 keal/mol) breaks more rapidly with the initial oxidative addition... 

Phenylazo-1,2,4-triazole were prepared from benzenediazonium chloride and 1,2,4-triazole <07SC1977>. 5-Aryltriazole acyclonucleosides 134 with various aromatic groups on the triazole ring were synthesized from precursor 133 via the Suzuki coupling reaction in aqueous solution and promoted by microwave irradiation <07TL2389>. 1-Methyl-1,2,4-triazole 135 participated in a palladium-catalyzed C-H arylation reaction with 3,5-dimethoxychlorobenzene 136 to give coupled product 137 <07OL1449>. 

Different conditions (including additives and solvent) for the reaction have been reported,often focusing on the palladium catalyst itself," or the ligand." Catalysts have been developed for deactivated aryl chlorides," and nickel catalysts have been used." Modifications to the basic procedure include tethering the aryl triflate or the boronic acid to a polymer, allowing a polymer-supported Suzuki reaction. Polymer-bound palladium complexes have also been used." " The reaction has been done neat on alumina," and on alumina with microwave irradiation." Suzuki coupling has also been done in ionic liquids," in supercritical... 

Old, D. W. Wolfe, J. P. Buchwald, S. L., A Highly Reactive Catalyst for Palladium-Catalyzed Cross-Coupling Reactions Room-Temperature Suzuki Couplings and Animation of Unactivated Aryl Chlorides. / Am. Chem. Soc. 1998, 120,9722. 

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]. 

Bergman described indole C-3 acylation with acid chlorides via l-indolylzinc chloride in the absence of palladium [105], Davidsen and co-workers synthesized 86, which is a potent antagonist of platelet activating factor-mediated effects, using this Bergman acylation sequence as shown [106]. As will be discussed in the next section, a Suzuki coupling was used to prepare 84. 

Suzuki coupling reaction of phenylboronic acids such as 74 with 4-bromopyridine [34]. Inada and Miyuara [35] have extended the method to 2-chloroquinoline 25. Therefore, the coupling between 25 and phenylboronic acid 74 led to 2-tolylquinoline 75 in 91% yield. The catalyst was recovered with ease and used in further coupling reactions. Not surprisingly, the couplings of phenylboronic acids with electron-rich chloroarenes were ineffective due to their slow oxidative addition to the palladium(O) complex. This reaction is an example where even quinolinyl chloride is a good substrate for the oxidative addition of Pd(0) if the chlorine atom is at the activated position (a or 8). 

The use of palladium attached to FibreCat catalysts in simple Heck and Suzuki reactions has already been described (1). This work has now been extended to cover a wider variety of FibreCat systems (Figure 1) in the more difficult Suzuki coupling of aryl chlorides (3,4). (NB FibreCat 1000-Dl, D2 and D3 are experimental samples, whereas 1000-D7, D8 and 1001 are all commercially... 

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