Silicon polypodands: a new class of efficient solid-liquid phase-transfer catalysts

Silicon polypodands 1-7 were found to be powerful complexing agents of alkali metal salts, even in low polarity media (chlorobenzene) and hence very efficient phase-transfer catalysts. Their catalytic activity was measured in typical anion-promoted reactions under solid-liquid phase-transfer catalysis (SL-PTC) conditions. It ismainly determined by the complexing ability of the ligand, increasing with the number of silicon atoms and binding sites. Comparison with traditional phase-transfer catalysts showed that these polypodands are better catalysts not only than open-chain PEG400Me2 and TRIDENT, but even than more sophisticated macrocyclic polyethers such as DCH18C6.