Tppts

Supported aqueous phase (SAP) catalysts (16) employ an aqueous film of TPPTS or similar ligand, deposited on a soHd support, eg, controlled pore glass. Whereas these supported catalysts overcome some of the principal limitations experienced using heterogeneous catalysts, including rhodium leaching and rapid catalyst deactivation, SAP catalysts have not found commercial appHcation as of this writing. 

Pd(OAc)2, TPPTS, CH3CN, H2O, 75 min. 100% yield. The Alloc group is readily released in the presence of this ester. 

The major advantage of the use of two-phase catalysis is the easy separation of the catalyst and product phases. FFowever, the co-miscibility of the product and catalyst phases can be problematic. An example is given by the biphasic aqueous hydro-formylation of ethene to propanal. Firstly, the propanal formed contains water, which has to be removed by distillation. This is difficult, due to formation of azeotropic mixtures. Secondly, a significant proportion of the rhodium catalyst is extracted from the reactor with the products, which prevents its efficient recovery. Nevertheless, the reaction of ethene itself in the water-based Rh-TPPTS system is fast. It is the high solubility of water in the propanal that prevents the application of the aqueous biphasic process [5]. 

Certain amines, when linked to TPPTS, form ionic solvents liquid at quite low temperatures. Bahrman [33] used these ionic liquids as both ligands and solvents for the Rh catalyst for the hydroformylation of alkenes. In this otherwise interesting... 

A ruthenium complex [RuCl2(TPPTS)2]2 was used for regeneration of NADP+ to NADPH withhydrogen. Thus, 2-heptanonewas reduced with alcohol dehydrogenase from Thermoanaerobacter brockii in the presence of the mthenium complex, NAD P, and hydrogen at 60°C to (S)-2-heptanol in 40 % ee. Turnover number was reported to be 18 (Figure 8.6) [5cj. 

Fackler, J.J., Grant, T.A., Hanson, B.E.and Staples, R.J. (1999) Characterisation of luminescent, homoleptic, three coordinate, water soluble Au(I) complex of trisulfonated triphenylphosphine (TPPTS) as the caesium salt, Cs8[Au(TPPTS)j]. 5.25H2O. Cold Bulletin, 31, 20-23. 

An example of a large scale application of the aqueous biphasic concept is the Ruhrchemie/Rhone-Poulenc process for the hydroformylation of propylene to n-butanal (Eqn. (15)), which employs a water-soluble rhodium(I) complex of trisulphonated triphenylphosphine (tppts) as the catalyst (Cornils and Wiebus, 1996). 

Similarly, Pd/tppts was used by Hoechst (Kohlpainter and Beller, 1997) as the catalyst in the synthesis of phenylacetic acid by biphasic carbonylation of benzyl chloride (Fig. 2.29). The new process replaces a classical synthesis by reaction of benzyl chloride with sodium cyanide, followed by hydrolysis of the resulting benzyl cyanide. Although the new process produces one equivalent of sodium chloride, this is substantially less salt production than in the original process. Moreover, sodium cyanide is about seven times as expensive per kg as carbon monoxide. 

Figure 2.29. Pd/tppt.s-catalysed carbonylations in aqueous biphasic media.

The C-C coupling through aqueous two-phase catalysis, is exemplified by reaction (17), which is carried out industrially in France. Here Ru with triphenylphosphine trisulphonate (TPPT) is used. 

Reaction conditions Catalyst H(CO)Rh(TPPTS)3, Rh 0.089 mmol, 1-octene/Rh = 426, CO/H2 (molar ratio) = 1, P(C0/H2) 400 psi, T = 100°C. Single-phase heptane only solvent, catalyst H(CO)Rh(PPh3)3. Linear/branched. 

In another interesting area in the study of hydroformylation, Davis developed the concept of supported aqueous phase (SAP) catalysis.175 A thin, aqueous film containing a water-soluble catalyst adheres to silica gel with a high surface area. The reaction occurs at the liquid-liquid interface. Through SAP catalysis, the hydroformylation of very hydrophobic alkenes, such as octene or dicyclopentadiene, is possible with the water-soluble catalyst [HRh(CO)(tppts)3]. 

Hydroaminomethylation of alkenes occurred to give both n- and /. so aliphatic amines catalyzed by [Rh(cod)Cl]2 and [Ir(cod)Cl]2 with TPPTS in aqueous NH3 with CO/H2 in an autoclave. The ratio of n-and /.soprimary amines ranged from 96 4 to 84 16.178 The catalytic hydroaminomethylation of long-chain alkenes with dimethylamine can be catalyzed by a water-soluble rhodium-phosphine complex, RhCl(CO) (Tppts)2 [TPPTS P(m-C6H4S03Na)3], in an aqueous-organic two-phase system in the presence of the cationic surfactant cetyltrimethy-lammonium bromide (CTAB) (Eq. 3.43). The addition of the cationic surfactant CTAB accelerated the reaction due to the micelle effect.179... 

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