Polymer water-soluble hydroformylation catalysts

Recently, rhodium/poly(enolate-co-vinyl alcohol-co-vinyl acetate) catalysts have been developed for the biphasic hydroformylation of aliphatic alkenes and applied to the selective hydroformylation of functionalized alkenes [16], Although the conversions were low (< 25%), excellent selectivities for the hydroformylation of n-bu-tyl vinyl ether and methyl 3,3-dimethylpenten-4-onate can be achieved with such water-soluble polymer-anchored rhodium catalysts. For instance, the hydroformylation of methyl 3,3-dimethylpenten-4-onate gives only the linear aldehyde. 

CAO-Norbornanecarboxaldehyde [Asymmetric Hydroformylation of an Alkene using a Cro.ss-Linkcd Polymer-Supported Catalyst under Heterogeneous Conditions]. n-Heptanal and 2-Metbylhexanal [Hydroformylation of an Alkene using Water-Soluble Complexes as Catalytic Precursors in a Two-Phase System]... 

The thermal instability of rhodium-based hydroformylation catalysts has already been overcome commercially in the Ruhrchemie/Rhone-Poulenc process for propene hydroformylation in which the sodium salt of a sulfonated triphe-nylphosphine ligand (TPPTS, la) is used to solubilize the catalyst in the aqueous phase. In this process, the second phase is toluene and the reaction is carried out as a batch process with rapid stirring to intimately mix the two immiscible phases. After reaction, the system is allowed to separate and the organic phase is simply decanted from the aqueous catalyst phase. Both water-soluble polymers and PAMAM dendrimers have been reported as supports for rhodium-catalyzed hydroformylation under aqueous biphase conditions, but reactivities and regioselec-tivities were only comparable to or worse than those obtained with the reference TPPTS ligand. The aqueous biphase approach has found limited application for the hydroformylation of longer-chain alkenes, because of their very low solubility in water leading to prohibitively slow reaction rates, but there have been a variety of approaches directed at the solution of this problem. 

The concept of SI L catalyst has been developed quickly in the last decade. Holderich et al. [4] added acidic chloroaluminate ILs to various types of supports, and the catalytic activities of the immobilized ILs were found to be higher than those of the conventional catalysts under the same conditions. Inspired by this work, SIL catalysts have been widely used in the coupling reactions for olefin hydroformylation [5], olefin metathesis [6], Heck reactions [7], and hydroamination [8], and so on. SIL catalytic systems have also been reported for some other reactions, such as water-gas shift reaction [9], dihydroxylation of olefins [10], and hydrogenation [1 Ij. The solid supports used include magnetic NPs [12], mesoporous molecular sieves [13], soluble organic ions [14], noncovalently solid-phase [15], IL-functionalized carbon nanotubes [16], polymer cocktail [17], and so on. 

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