Palladium-catalyzed coupling Suzuki reaction

The first report of the synthesis of )S-keto sulfoxides using a palladium-catalyzed carbonylative Suzuki reaction of a-bromosulfoxide with arylboronic acids appeared in 2005 [28]. Asensio and his associates described the synthesis of 12 different /f-keto sulfoxides in moderate to excellent yields using Pd(PPh3)4 and CsF as the base in the presence of 1 bar CO (Scheme 4.13). The carbonylative coupling reaction is strongly favored over the competing non-carbonylation and homocoupling processes. However, the chemoselectivity drops and by-products... 

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,... 

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]. 

The Fukuyama indole synthesis involving radical cyclization of 2-alkenylisocyanides was extended by the author to allow preparation of2,3-disubstituted derivatives <00S429>. In this process, radical cyclization of 2-isocyanocinnamate (119) yields the 2-stannylindole 120, which upon treatment with iodine is converted into the 2-iodoindole 121. These N-unprotected 2-iodoindoles can then undergo a variety of palladium-catalyzed coupling reactions such as reaction with terminal acetylenes, terminal olefins, carbonylation and Suzuki coupling with phenyl borate to furnish the corresponding 2,3-disubstituted indoles. 

The palladium-catalyzed coupling of boronic acids with aryl and alkenyl halides, the Suzuki reaction, is one of the most efficient C-C cross-coupling processes used in reactions on polymeric supports. These coupling reactions requires only gentle heating to 60-80 °C and the boronic acids used are nontoxic and stable towards air and water. The mild reaction conditions have made this reaction a powerful and widely used tool in the organic synthesis. When the Suzuki reaction is transferred to a solid support, the boronic add can be immobilized or used as a liquid reactant Carboni and Carreaux recently reported the preparation of the macroporous support that can be employed to efficiently immobilize and transform functionalized arylboronic adds (Scheme 3.12) [107, 246, 247]. 

The Suzuki reaction was used in liquid crystal syntheses67 to modify the properties of a polymer by the introduction of aromatic groups to a boronic acid functionalized backbone. Palladium-catalyzed couplings have found wide use in this field.68,69... 

The examples reported to date do not allow a clear ranking of palladium catalysts with regard to their ability to catalyze the Suzuki reaction. It should also be kept in mind that palladium(O) complexes are air-sensitive, and the quality of commercially available catalysts of this type can vary substantially. Some successful Suzuki couplings are listed in Table 5.12. Further examples have been reported [184,186-196],... 

C-Arylation of indoles can be accomplished by means of palladium-catalyzed coupling reactions, such as the Suzuki coupling (Entry 7, Table 15.7) or Stille coupling with resin-bound 2-bromoindoles [88] or 5-bromoindoles [75]. 2-Iodoindoles have been prepared on polystyrene by iododesilylation of 2-silylindoles with NIS (Entry 8, Table 15.7), and these can be C-arylated with arylboronic acids [73]. 

The palladium-catalyzed coupling of boronic acids (as well as other boron derivatives) with aryl and vinyl halides and psendohalides is known as the Suzuki or Suzuki-Miyaura reaction. Because boron is nontoxic, this reaction has been used in pharmaceutical syntheses. In addition, hydroboration or borate substitution allows for the synthesis of virtually any desired coupling partner. For these reasons, as well as the high yields and functional group compatibility, the Suzuki reaction is the first reaction to consider for carrying out a cross coupling. Representative substrates and catalysts are shown in Scheme 17. The various bases are used to generate four-coordinate boron ate complexes that are more reactive in transmetalation. 

The Suzuki reaction is a palladium-catalyzed coupling of an organic halide (R X) with an organoborane (RBY2) to form a product (R-R ) with a new C-C bond. Pd(PPh3)4 is the typical palladium catalyst, and the reaction is carried out in the presence of a base such as NaOH or NaOCH2CH3. 

Suzuki reaction (Section 26.2) The palladium-catalyzed coupling of an organic halide (R X) with an organoborane (RBY2) to form a product R—R . 

Palladium-catalyzed coupling reactions of 2-(5-iodoisoxazol-3-yl)pyridine 274 with a variety of organometallic compounds led to derivatives 275-278 through Sonogashira, Suzuki, Negishi, and Stille reactions, respectively (Scheme 64) <20010L4185>. 

Alkylboronic acids and arylboronic acids, RB(OH)2, and ArB(OH)2, respectively, are increasingly important in organic chemistry. The palladium catalyzed coupling reaction of aryl halides and aryl triflates with arylboronic acids (the Suzuki-Miyaura... 

Miyaura, N., Suzuki, A. Paiiadium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds. Chem. Rev. 1995, 95, 2457-2483. Stephenson, G. R. Asymmetric palladium-catalyzed coupling reactions (ed. Stephenson, G. R.) (Chapman Hall, London, 1996) 275-298. Browning, A. F., Greeves, N. Palladium-catalyzed carbon-carbon bond formation (eds. Beller, M.,Bolm, C.) (Wiley-VCH, Weinheim, New York, 1997) 35-64. 

The reader is also directed to Section 12.7.C for a palladium-catalyzed coupling reaction involving boronic acids called Suzuki coupling. 

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