Suzuki-Miyaura-type

Recently we have reported a preliminary communication on Suzuki—Miyaura type of cross-coupling of 6-... 

Bedford and coworkers disclosed iron-catalyzed Suzuki-Miyaura-type coupling reactions of benzyl bromides with sodium tetraphenylborate in the presence of 5 mol% 15 as the catalyst and 10 mol% of dianisylzinc as a promoter. No reaction occurred in its absence. The coupling furnished 38-88% yield of 3 (entry 26) [66]. The transformation proceeds probably by initial B-Zn transmetalation. The resulting arylzinc transfers the aryl group to the iron catalyst as in the Negishi couplings above. An aryliron(I) complex was proposed to be formed initially. 

Powell, Maki, and Fu reported a Ni-catalyzed tandem radical 5-exo cyclization/ Stille coupling reaction (Fig. 19) [75]. When allylic bromo ethers 80 were subjected to a reaction with trichlorophenylstannane 81a in the presence of 10 mol% NiCl2 and 15 mol% of bipy 26, bicyclic phenyl-substituted products 82 were isolated in 57-67% yield and moderate to excellent endo-diastereoselectivity. Suzuki-Miyaura-type coupling reactions of 80 with arylboronic acids 81b worked similarly in 69-87%... 

Rhodium has been successfully used in a range of Suzuki-Miyaura type reactions. Satoh and Miura have reported the Suzuki-Miyaura-type cross-coupling of arylboron compounds with aryl halides in the presence of a rhodium-based catalyst system to produce the corresponding biaryls (Scheme 13.21). They also found, unexpectedly, that when employing benzonitrile as substrate under similar reaction conditions a multiple arylation is observed, in which nucleophilic arylation on the cyano group and subsequent ortho arylation via C-H bond cleavage is involved. 

Scheme 53 Suzuki-Miyaura-type coupling of arylboronic adds with 2-bromothiophene [171] Palladium-Catalyzed Coupling Reactions...

In 2004 Kakiuchi disclosed that atkoxyarenes bearing an ortho carbonyl group can be coupled with arylboronic esters in the presence of RuH2(CO)(PPh3)3 [Eq. (16)] [65]. The reaction represents the first example of a Suzuki-Miyaura-type reaction of aryl ethers. Chelation assistance facilitates the oxidative addition of C-O bonds, which allows for a regioselective C-O bond cleavage of diaryl ethers. 

The nickel-catalyzed Suzuki-Miyaura-type C-O bond arylation has been successfully applied to steroidal architecture (Scheme 4). A hydroxyl moiety in estrone can readily be substituted by an array of aryl groups under nickel catalysis via conversion into pivalate instead of the typically used triflate [38]. The carbonyl moiety in estrone also serves as a suitable precursor for an alkenyl C-O electrophile. Treatment of estrone with 2-propenyl acetate affords the compounds bearing two acetate groups, both of which are potentially reactive toward nickel-catalyzed cross-coupling. However, selective arylation took place at the alkenyl position, and... 

Directed orf/to-metalation (DoM) chemistry [81] further reinforces the versatility of nickel-catalyzed C-O bond activation reactions. Based on the strong accelerating and orf/to-directing effect of carbamate functionality in the base-induced deprotonation of arenes, an array of electrophiles can be introduced at the ortho position of aryl carbamates. For instance, DoM of dicarbamate, followed by 1,2-addition to a,(3-unsaturated aldehyde and intramolecular cyclization, furnishes the 2//-chromene derivative (Scheme 8) [82]. The carbamate director can finally be arylated under a nickel-catalyzed Suzuki-Miyaura-type reaction [47]. 

Not only Grignard reagents but also boronates may be employed as nucleophiles in iron-catalyzed cross-coupling. Aryl iodides and bromides react in a Suzuki-Miyaura-type coupling with arylboronic acids in the presence of 10 mol% iron(lll) chloride and a stoichiometric amount of potassium fluoride in ethanol at 100 °C under air to give the corresponding biaryl compounds with good to excellent yields (Scheme 4-227). ... 

Cazin and co-workers recently reported on the use of the well-defined dimer complexes [Pd( a-C1)(C1)(NHC)]2 that are commercially available, and perform exceedingly well in the Suzuki-Miyaura reaction involving aryl chlorides [108]. The Cazin group has also recently disclosed well-defined mixed NHC/phosphite palladium systems of the type [PdCl2(NHC) P(OR)3j], enabling the Suzuki-Miyaura of aryl chlorides at 0.1 mol% Pd loading [109]. 

Inamoto and Doi have also worked on pincer-type biscarbene complexes of nickel(II). Pre-catalyst 20 was successfully applied to the Suzuki-Miyaura reaction... 

The scope of Suzuki-Miyaura reactions is extremely broad, covering practically all types of organic residues. The cross-coupling of arylboronic acids with aryl halides or triflates is the most... 

The pincer-type palladacycle (120) (R = 1Pr), which is actually a derivative of a dialkylphos-phinous acid (themselves excellent ligands see Section 9.6.3.4.6) was shown to allow the crosscoupling of aryl chlorides with terminal acetylenes ((120), ZnCl2, Cs2C03, dioxane, 160 °C). However the high reaction temperature may be prohibitive for the actual application of this catalytic system, as acetylenes are known to be thermally sensitive.433 The same palladacycle (R = Ph) is effective in the Suzuki-Miyaura reaction with aryl bromides and activated aryl chlorides (K2C03, toluene, 130 °C). 

A variety of triazole-based monophosphines (ClickPhos) 141 have been prepared via efficient 1,3-dipolar cycloaddition of readily available azides and acetylenes and their palladium complexes provided excellent yields in the amination reactions and Suzuki-Miyaura coupling reactions of unactivated aryl chlorides <06JOC3928>. A novel P,N-type ligand family (ClickPhine) is easily accessible using the Cu(I)-catalyzed azide-alkyne cycloaddition reaction and was tested in palladium-catalyzed allylic alkylation reactions <06OL3227>. Novel chiral ligands, (S)-(+)-l-substituted aryl-4-(l-phenyl) ethylformamido-5-amino-1,2,3-triazoles 142,... 

Other successful examples of catalysts containing NHC ligands are found in palladium- and nickel-catalyzed carbon-carbon bond formations. The catalyst development with these metals has focused in particular on Heck-type reactions, especially the Mizoroki-Heck reaction itself [Eq. (42)] and various cross coupling reactions [Eq. (43)], e.g., the Suzuki-Miyaura reaction ([M] = and the Kumada-Corriu reaction ([M] = MgBr). " Related reactions like the Sonogashira coupling [Eq. (44)]326-329 Buchwald-... 

In conclusion, the application of the Suzuki—Miyaura reaction of 6-chloropurine derivatives with substituted phenylboronic acids is a facile and effective approach for the synthesis of a series of specifically substituted 6-phenylpurine bases and nucleosides. In comparison with the previously known methods25-30 using other types of organometallic reagents or photochemistry, this method is more effective and selective, and therefore, further applications in the synthesis of 6 C-substituted purine derivatives may be expected. 

An efficient aqueous phase Suzuki-Miyaura reaction of activated aryl chlorides with aryl boronic acids has been reported. The method uses a new D-glucosamine-based dicyclohexylarylphosphine ligand for the palladium catalyst and works well with nitro-and cyano-activated chlorides.32 The aryl fluoride bond has been considered inert to palladium-catalysed substitution reactions. However, a computational study, backed up by experiment, shows that the presence of a carboxylate group ortho to fluorine will allow reaction both with phenylboronic acids in a Suzuki-type reaction and with organotin reagents in a Stille-type reaction the presence of the adjacent oxyanion stabilizes the transition state.33... 

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