Rh-Catalysed Hydroformylation Of Higher Olefins

The hydroformylation of alkenes is an important method for the production of aldehydes in industrial applications, in which a key concern is to establish a catalytic system that can realize the combination of high efficiency and long life of catalyst. In this study, the zwitterionic phosphines ligands with lysine tags were designed and synthesized based on the concept of "ionic tag" for hydroformylation of higher olefins. A "homogeneous catalysis-immobilization separation" catalytic system was developed based on zwitterionic phosphines ligands. Under this catalytic system, the hydroformylation takes place in a homogeneous medium containing methanol/ionic liquid and the Rh-catalysts can be recovered by extracted with n-heptane. The Rh-catalysts were reused17times with0.3-0.4%of Rh leaching without significant loss of catalytic efficiency, in which the formation of dimethylacetals is a vital step for inhibiting the Rh-catalyst loss in the hydroformylation.Owning to the reactivity of aldehyde group, the formation of acetal may be used to protect the sensitive aldehyde group or to further synthesize fine chemicals. Based on the atom economy and low energy consumption principles in green chemistry, the hydroformylation of alkenes can be combined with acetalization reaction to form tandem reaction sequences. In this study, A robust and highly active and selective tandem hydroformylation-acetalization of olefins using acid-Rh bifunctional catalysts (ARBCs) in ionic liquid/alcohol systems is reported. The key feature of the Rh catalyst is its use of the zwitterionic phosphine ligand bearing an amino acid tag. This novel catalytic system can efficiently immobilize the Rh-catalyst and shows no significant loss of activity, selectivity or Rh for more than seventeen cycles. We believe that the high acetal selectivity mainly depends on the synergy between the acidic active site and the Rh active site on the ARBCs.To design and synthesize customized ILs with functionalized cations or anions that match the commercial phosphine ligand is a simpler and more economic means to realize highly effective immobilization of Rh catalyst. In this study, the novel room temperature-solidifiable polyether guanidinium ionic liquids (PGILs) were designed and synthesized for hydroformylation of higher olefins. In the light of the main disadvantages such as poor mass transfer and fast catalyst deactivation existing in the ionic liquid biphasic hydroformylation, a novel "homogeneous catalysis and two-phase separation" catalytic system is established based on PGILs. This catalytic system combines the advantages of both the homogeneous and the biphasic hydroformylation, hence enabling super long-term high activity and selectivity with much simplified separation and recycling of Rh catalyst. No significant loss of activity, selectivity or Rh was observed after forty-seven cycles, and the turnover number (TON) reached above40000. To the best of our knowledge, no comparable results have been reported for biphasic hydroformylation in ILs.