TPPTS ligand Heck reaction

Tppts is a white solid which is slightly air sensitive. Deaerated solutions of tppts are stable if stored under inert gas atmosphere. The 31P NMR (161.8 MHz, D20) exhibits a singlet at 8 — 5.1 ppm. Detailed NMR data can be found in reference 19. Tppts is widely used as a ligand for metal-catalyzed reactions in water (e.g., hydrogenation, hydroformylation, carbonylation, and Heck reactions).1... 

Initially, only dipolar aprotic solvents such as W,A -dimethylformamide (DMF), N-methylpyrrolidinone (NMP), dimethyl sulfoxide (DMSO), and acetonitrile (MeCN) were common (Table 3-2). However, the presence of water has been found to accelerate certain Heck reactions [17], and consequently the development has gone to water-soluble tiiarylphosphane ligands (e.g triphenylphosphane w-trisulfonate sodium salt (TPPTS) [18a], with which many alkene arylations succeed superbly in aqueous solvent mixtures [19]. 

Water-soluble Ru-EDTA complexes are active carbonylation eatalysts for the conversion of amines to amides [158]. TPPTS (and other water-soluble ligands, other additives included) have been used for special carbonylations [159, 203, 238]. For other types of carbonylation and Heck reaction, see Sections 2.1.2.3 and 3.1.6. 

The Mizoroki-Heck reaction was carried out in water/scCOz and ethylene glycol /scC02 using the typical sulfonated triphenylphosphine ligand TPPTS [56]. The reaction is claimed to occur under monophasic conditions although this seems unlikely under the C02 pressures and temperatures with the amounts of catalyst and co-solvent employed. Catalyst recycling was achieved by phase separation after... 

Another biphasic Heck reaction was described by Beller et al. [25]. The medium consisted of xylene and ethylene glycol. The catalyst was a palladium complex with a carbohydrate-substituted triphenylphosphine (9 and 10). Aryl bromide (15 mmol), styrene (22.5 mmol), and NaOAc (16.5 mmol) were suspended in 10 mL of xylene and 10 mL of ethylene glycol. The catalyst precursor (Pd(OAc)2) and ligand (Pd/ ligand ratio 1 3) were added and the mixture was heated to 130 °C for 20 h. Both ligands A and B showed better results than the TPPTS ligand (cf Section 2.2.3.2) in the case of activated aryl bromides (for instance, p-nitrobromobenzene). However, for deactivated aryl bromides (for instance, 2-bromo-6-methoxynaphthalene) TPPTS proved to generate a more stable and thus more productive catalyst system. 

Triphenylphosphane monosulfonate (sodium salt) and triphenylphosphine disulfonate (disodium salt) were compared in one study with TPPTS and the results showed that each ligand together with 1.0mol% palladium catalyst is similarly effective for the Mizoroki-Heck reaction of iodobenzene with an olefin [162], Leaching levels are also comparable the percentaged leaching represents the amount of palladium contamination... 

Palladium is one of the most versatile and efficient catalyst metals in organic synthesis. Solubility in water is achieved by utilization of simple palladium(II) salts or water-soluble ligands, such as TPPTS and TPPMS. The active catalysts for Heck-type reactions are zerovalent palladium(O) species [3], which are often generated in situ by thermal decomposition of a Pd(II) precursor or by the application of a reducing agent, e.g., 1-6 equiv. of a phosphine in the presence of base generates Pd(0) and the phosphine oxide (Eq. 3) [4],... 

Scheme 10.16 Nickel-catalysed Mizoroki-Heck-type reactions with TPPTS (53) as ligand.

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