Oleyl hydroformylation

The prototype reaction was the hydroformylation of oleyl alcohol (water insoluble) with a water-soluble rhodium complex, HRh(C0)[P(m-C6H4S03Na)3]3 (Figure 6.5). Oleyl alcohol was converted to the aldehyde (yield = 97%) using 2 mol % Rh with respect to the substrate and cyclohexane as the solvent, at 50 atmospheres CO/H2, and 100°C. The SAPCs were shown to be stable upon recycling, and extensive work proved that Rh is not leached into the organic phase. Since neither oleyl alcohol nor its products are water soluble, the reaction must take place at the aqueous-organic interface where Rh must be immobilized. Also, if the metal catalyst was supported on various controlled pore glasses with... 

Another method for catalyst recycling was introduced by Davies and Hanson [38]. The heterogenization of the rhodium catalyst in an aqueous phase on a silica carrier enabled simple catalyst separation via filtration. Oleyl alcohol was hydroformylated in a thin aqueous phase on the catalyst surface at 50 bar and 100°C. Under these conditions, the yield was 97%, while the catalyst could be recycled several times without any loss of activity. 

Supported aqueous-phase catalysts can also be used to advantage. These supported catalysts have a thin aqueous film adhering to silica gel that contains the water-soluble complex (131). These catalysts are particularly useful for the hydroformylation of substrates such as oleyl alcohol (132). Since these catalytic reactions occur at the phase boundary, characteristics such as the water content can cause changes both in the reactivity and in the linear branched chain ratio of the product aldehyde. 

Rhodium complexes modified with polyether phosphine oxides according to the Structure 30 were used as catalysts for the hydroformylation of 1-decene and oleyl alcohol in micellar aqueous-biphase systems [56, 57]. 

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. 

The development of supported aqueous-phase catalysis (SAPC) opened the way to hydroformylating hydrophobic alkenes such as oleyl alcohol, octene, etc. (cf. Section 4.7 [17]). SAPC involves dissolving an aqueous-phase HRh(CO)(TPPTS)3 complex in a thin layer of water adhering to a silica surface. Such a catalyst shows a significantly high activity for hydroformylation. For classical liquid-liquid systems, the rate of hydroformylation decreases in the order 1-hexene > 1-octene > 1-decene however, with SAP catalysts, these alkenes react at virtually the same rate and the solubility of the alkene in the aqueous phase is no longer the ratedetermining factor [26]. 

Hydroformylation of the water-insoluble oleyl alcohol into formylstearyl alcohol has also been successfully achieved with a 96.6% yield by using a rhodium/trisul-fonated triphenylphosphine complex dissolved in an aqueous film supported on a high-surface-area silica gel (cf. Section 6.1) [13]. This supported catalyst has also been used to perform the hydroformylation of allyl 9-decenyl ether and 3-methyl-2-(2-pentenyl)-2-cyclopenten-l-one (as-jasmone). However, with the latter substrate, the aldehyde yields did not exceed 38% [14],... 

In the early experiments [18] the hydrogenation or hydroformylation of oleyl alcohol into the corresponding saturated alcohol and aldehyde, all products being completely insoluble in water, was performed with success. The authors have considered that the reaction is occurring at the organic-aqueous film interface. Further experiments carried out by Horvath have confirmed this interpretation [19]. Indeed, several olefins of different carbon chain length are functionalized at the same rate, more precisely at the same turnover frequencies (TOFs). Olefins with up to 17 carbon atoms can be transformed [14]. 

Hydroformylation of oleyl alcohol into formylstearyl alcohol has been successfully achieved with a 96.6% yield by using a Rh/TPPTS complex dissolved in an aqueous... 

Supported aqueous phase catalysts are well known [29, 30]. In these systems, a thin film of water present on the surface of a polar solid support is used to immobilize metal complexes, which are nonvolatile or insoluble in a mobile gaseous or liquid organic phase, respectively [30]. The concept was used successfully, for example, for the hydroformylation of oleyl alcohol over a supported rhodium complex [29]. Here, it was suggested that the reaction occurred at the interface between the aqueous and organic phase. However, the volatility of water necessitated... 

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