Suzuki water-soluble phosphine ligands

Akin to (—)-stipiamide (28) is (-)-myxalamide A (29), the , , Z, , -pentaene portion having been fashioned via the alternative Suzuki process between a vinyl catecholborane (formed in situ via hydroboration of alkyne 33) and Z-vinyl iodide 32 (Scheme 15). Using catalytic Pd(OAc)2 and the water-soluble phosphine ligand TPPTS, coupling in aqueous CH3CN at room temperature gave the desired natural product in 44% isolated yield as a pure isomer. 

To effect aqueous Suzuki-Miyaura reactions, water-soluble phosphine ligands have been explored. Miyaura and coworkers [122] reported that a palladium catalyst based on the water-soluble N-(4-diphenylphosphino)phenyl-methylgluconamide (GLCAphos, 40) was effective at low loadings for the Suzuld-Miyaura couphng of activated aryl chlorides in water (Scheme 6.26). 

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... 

The first examples of water-soluble alkylphosphines that were capable of promoting Suzuki couplings of aryl bromides in aqueous solvents at room-temperature were monodentate phosphines 98 and 99 (Scheme 1.64). Catalysts derived from them showed high activity towards aryl bromides, with TONs up to 10 000 at rt, which increased up to 734 000 at 80 °C, while the more sterically demanding ligand 99 gave catalysts with a superior activity towards aryl... 

Fluorenyldialkylphosphines represent another interesting class of trialkyl-phosphines that can be used for Suzuki couphngs of aryl chlorides. Sulfonylation of the aromatic moiety of the fluorenyl group results in a water-soluble ligand that can be used for couplings in aqueous solvent (Equation 2.20) [35-37]. 

D.iii.d. Miscellaneous. The Suzuki reaction in the presence of either TPPMS ligand or phosphine-free mode has successfully been applied for the preparation of water-soluble polyphenylenes containing carboxylic (Scheme or sulfonato groups. 

Ligand 19 is water soluble, and has been employed in Suzuki coupling reactions conducted in aqueous media. Ligand 17 provides optimal results in Suzuki coupling reactions of aryl tosylates and aryl benzenesulfonates. Ligand 16 is thought to have the greatest substrate scope of the Buchwald biaryl-phosphine derivatives, and is widely used in... 

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