Aryl Suzuki cross-coupling

FuNn iONAL Group Tolerance of PdildbrO VIMes.HCI Catalyzed Suzuki Cross-Coupling Reactions of Aryl Chlorides with Phenyi.boronic Acid Derivatives... 

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... 

Synthesis of unprotected 4-aryl phenylalanine by Suzuki cross-coupling reactions. 

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]. 

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]). 

In a simple strategy to biaryl formation, Han et al.89 showed that silicon-directed ipso-substitution and concomitant cleavage from supports could be used for formation of functionalized biphenyls. For this they used a tethered silyl aryl bromide in a Suzuki cross-coupling reaction, followed by the ipso-substitution/cleavage step (Scheme 39). A variety of boronic acids were coupled in this manner. The only difficulty occurred with electron-deficient nitrophenylboronic acid where the desired product was formed under anhydrous conditions in only 33% yield (the remainder being starting material). Reversion to the more usual conditions of aqueous base-DME (i.e., those used by Frenette and Friesen)70 improved the yield to 82%. 

Boukouvalas J, Lachance N, Ouellet M, Tmdeau M (1998) Facile Access to 4-Aryl-2(5//)-furanones by Suzuki Cross Coupling Efficient Synthesis of Rubrolides C and E. Tetrahedron Lett 39 7665... 

Schliiter et al. successfully accomplished generation-specific incorporation of an individual aryl bromide functionality into poly(benzyl ether) dendrimers. Whatever its position in the dendrimer framework, this bromide function could also be utilised for further chemical modification because it can react with aryl-boronic acid via Suzuki cross-coupling [42]. 

Peyroux, E. Berthiol, F. Doucet, H. Santelli, M. Suzuki cross-coupling reactions between alkenylboronic acids and aryl bromides catalysed by a tetraphosphane-Pd catalyst. Eur. J. Org. Chem. 2004, 1075-1082. 

Chaumeil, H. Signorella, S. Le Drian, C. Suzuki cross-coupling reaction of sterically hindered aryl boronates with 3-iodo-4-meth-oxybenzoic add methyl ester. Tetrahedron 2000, 56, 9655-9662. 

Griffiths, C. Leadbeater, N. E. Palladium and Ni-catalyzed Suzuki cross-coupling of sterically hindered aryl bromides with PhB(OH)2. Tetrahedron Lett. 2000, 43, 2487—2490. 

Leadbeater and Griffiths developed palladium catalysts for the Suzuki cross-coupling of aryl halides bearing two ortho substituents with phenylboronic acid, and used them in the synthesis of sterically hindered biaryls [83]. 

Most recently, Monteiro et al. have reported that cyclopalladated compounds derived from the ortho-metalation of benzylic tert-butyl thioethers are excellent catalyst precursors for the Suzuki cross-coupling reaction of aryl bromides and chlorides with phenylboronic acid under mild reaction conditions. A broad range of substrates and functional groups are tolerated in this protocol, and high catalytic activity is attained (Eq. (58)) [93]. 

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