Pillar5arenes as Supramolecular Hosts in Aqueous Biphasic Rhodium‐Catalyzed Hydroformylation of Long Alkyl‐chain Alkenes

Aqueous biphasic catalysis continues to attract strong interest, especially when very hydrophobic substrates are concerned. Indeed, their insolubility in water strongly limit their transformation by water‐soluble organometallic catalysts. To improve contacts between the substrate‐containing organic phase and the catalyst‐containing phase, one of the best solutions consists in using interfacial additives capable of supramolecularly recognize the substrate and/or the catalyst. In the present study, modified pillar5arenes are considered as interfacial additives and their performance is assessed in Rh‐catalyzed hydroformylation of long alkyl‐chain alkenes (higher olefins). Pillar5arenes substituted by carboxylate functions and methyl groups P5 A‐(Me)10‐x‐(CH2COOMe)x are compared to pillar5arenes substituted by polyethylene glycol (PEG) chains (P5 A‐(Me)5‐(PEG)5 and P5 A‐(PEG)10). Utilization of P5 A‐(Me)10‐x‐(CH2COOMe)x leads to high conversion and regioselectivity (linear/branched aldehyde ratio) in Rh‐catalyzed hydroformylation of 1‐decene and 1‐hexadecene. Compared with other interfacial additives such as modified cyclodextrins, the studied pillar5arenes show lower chemo‐selectivity, similar catalytic activity and higher regioselectivity.