Polyoxaethylene polypodands - powerful reduction catalysts in solid-liquid and liquid-liquid phase transfer systems

Abstract

aThe excellent catalytic properties of polypodands, esters of inorganic acids, as phase-transfer catalysts have been reported previously. Unfortunately, these compounds are unstable under hydrolytic conditions. A group of new, hydrolytically stable podands has been synthesized. Their complex forming abilities towards alkali metal ions have been studied. The podands studied have been used as catalysts in phase transfer catalysis conditions. The kinetics of this process has been determined. All compounds prepared have been found to complex metal ions and are a powerful catalysts in reduction of ketones by borohydrides in solid-liquid and liquid-liquid systems. Copyright

State Of The Art Of Supported Phase Transfer‐Catalysts Onium Salt‐Based

“…They are more stable to high temperatures than the corresponding quaternary ammonium salts and for this reason, they are also used for other applications such as ionic liquids and tools for peptide synthesis, despite the fact that they can form easily ylides under basic conditions in comparison with the ammonium ones a lot of various strategy has been developed to overcome this pifall. [4c] A valid alternative to quaternary onium salts is represented by macrocyclic scaffold such as crown ethers [8] (e. g. 3, 4 Figure 2), cryptands [9] (e. g. 5 Figure 2), polypodands [10] (e. g. 6, 7 Figure 2), cyclic peptoids [11] (e. g. 8 Figure 2), calixarenes [12] (e. g. 9 Figure 2), cyclodextrins [13] (e. g. 10 Figure 2).…”