Thermoregulated catalysis

Jin Z, Zheng X (1996) Thermoregulated Phase-transfer Catalysis. In CornUs B, Hermann WA (eds) Aqueous-Phase Organometallic Catalysis, Chap. 4, Sect. 6.3. Wiley, Weinheim, p 233... 

Keywords Immobilization Thermoregulated catalysis Thermomorphic ligands Hydroformylation Polyethylene glycol modified phosphites... 

Fig.1 The general concept of thermoregulated phase-transfer catalysis (TRPTC)...

The opposite temperature-dependent solubility of ligands in organic solvents is applied in the thermoregulated phase-separable catalysis (TRPSC) first published by Jin and coworkers [17] in 2000. The general principle is shown in Fig. 2 [10]. 

Thermoregulated phase-transfer and phase-separable catalysis are attractive catalyst recycUng techniques complementing other approaches of multiphase catalysis. They utilize temperature-dependent solubility or miscibiUty phenomena to switch between homogeneous reaction and heterogeneous separation stages. 

Hermanns E, Hasenjager J, Driefien-Holscher B (2008) PEG-Modified Ligands for Catalysis and Catalyst Recycling in Thermoregulated Systems. 23 53-66 Hermanns J, see Schmidt B (2004) 13 223-267 Herrmann W, see Freimd C (2007) 22 39-77... 

Thermoregulated Phase Transfer Catalysis - A conceptual advance in the field of biphasic hydroformylation of higher olefins is the use of rhodium catalysts generated from nonionic tenside phosphines, such as ethoxylated tris(4-... 

Because of their low solubilities in the aqueous phase, the hydroformylation of higher alkenes (>C2) is still a challenging problem. In addition to fluorous biphasic catalysis, possible solutions, which have been addressed, include the addition of surfactants240,241 or the use of amphiphilic ligands242-244 to enhance mutual solubility or mobility of the components across the phase boundary and thereby increase the rate of reaction. The use of polar solvents such as alcohols,245 p-cyclodextrin,246 cyclodextrin ligands,247 248 thermoregulated phase-transfer... 

Another interesting technique to solve the problem of mass transport in bipha-sic reactions was developed by Fell and Jin, the catalysis with so-called thermo-regulated phase transfer ligands [177-185] (details see Section 4.6.3). In the examples given so far, a smart solvent system controlled the phase behaviour of the reaction mixture. Lemaire et al. have found that also polyether-functionalized chiral mono- or diphosphites are active in thermoregulated conversion [186]. The hy-droformylation of styrene yields conversions of 99%, n/i-ratios of 85/15 and an enantioselectivity of up to 25%. A recycling of the catalyst proved to be possible, however, with a certain leaching of the rhodium catalyst. 

Thermoregulated Phase-transfer and Thermoregulated Phase-separable Catalysis... 

Thermoregulated Phase-transfer Catalysis with Nonionic Water-soluble Phosphines... 

Thermoregulated phase-transfer catalysis, however, could be successfully put into effect for the hydroformylation of higher olefins in aqueous/organic two-phase media [11], As shown in Table 2, various olefins have been converted to the corresponding aldehydes in the presence of nonionic phosphine-modified rhodium complexes as catalysts. An average turnover frequency (TOF) of 250 h-1 for 1-do-decene and 470 Ir1 for styrene have been achieved. Even the hydroformylation of oleyl alcohol, an extremely hydrophobic internal olefin, would give a yield of 72% aldehyde [19]. In comparison, no reaction occurred if Rh/TPPTS complex was used as the catalyst under the same conditions. 

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