Sulfonates Suzuki coupling

Several microwave-assisted protocols for soluble polymer-supported syntheses have been described. Among the first examples of so-called liquid-phase synthesis were aqueous Suzuki couplings. Schotten and coworkers presented the use of polyethylene glycol (PEG)-bound aryl halides and sulfonates in these palladium-catalyzed cross-couplings [70]. The authors demonstrated that no additional phase-transfer catalyst (PTC) is needed when the PEG-bound electrophiles are coupled with appropriate aryl boronic acids. The polymer-bound substrates were coupled with 1.2 equivalents of the boronic acids in water under short-term microwave irradiation in sealed vessels in a domestic microwave oven (Scheme 7.62). Work-up involved precipitation of the polymer-bound biaryl from a suitable organic solvent with diethyl ether. Water and insoluble impurities need to be removed prior to precipitation in order to achieve high recoveries of the products. 

Scheme 12.16 Microwave-assisted aqueous Suzuki couplings with PEG-bound aryl halides or sulfonates.

It is used for making NHCs for metal catalysed a-arylation of acychc ketones, e.g. propiophenones, and amination of haloarenes [Matsubara et al. J Org Chem 72 5069 2007], It has been sirlfonated for making sulfonated anilines, and consequently sulfonated NHCs, which provide water soluble Pd-NHCs used for Suzuki coupling of arylhalides with arylboronic acids in aqueous medium [Fleckenstein et al. Chem Commun 2870 2007],... 

Sulfonated ACPs are prepared both by direct sulfonation and by polycondensation and polycyclocondensation of sulfonated compounds. Synthesis of the first sulfonated poly(p-phenylene) was reported by Wegner and co-workers [103]. The Suzuki coupling of diboronic ethers with dibromo-aromatic monomers furnished poly(p-phenylene) with 95% yield. 

Monomers with pendant methoxyphenyl groups can be synthesized by the bromination of bis(4-fluorophenyl)sulfone, followed by a Suzuki coupling with4-methoxybenzeneboronic acid [22], The synthesis is shown in Figure 7.4. 

The first water-soluble, electroactive, self-doped sulfonatoalkoxy-substituted PPP, poly[2,5-bis(3-sulfonatopropoxy)-l,4-phenylene-aZf-l,4-phenylene] (55), was synthesized from 1,4-benzenediboronic acid [4612-26-4] (56) and the disodium salt of l,4-dibromo-2,5-bis(3-sulfonatopropoxy)benzene (57) by the homogeneous Suzuki coupling method (130). The polymer purified by dialysis of an aqueous solution was composed exclusively of 1,4-linkages. The abihty to utilize a variety of bis(boronic acids) in this polymerization with sulfonate containing aiyl hahdes will lead to a high degree of structural control of the optoelectronic properties of these water-soluble poljnners. 

Bromide resin 5 underwent Suzuki coupling (eq 5), and amine resin 6 reacted with isocyanates (eq 6), acid chlorides, and a sul-fonyl chloride. All resin-bound products were cleaved by displacement of the sulfonate linker with diethylamine in 23->95% isolated yield, and in ca. 90% purity. ... 

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