Synthesis and Characterization of Large (30-60-Membered) Aliphatic Crown Ethers

Article abstract of DOI:10.1021/jo00087a040

We report a new synthetic approach to large (30-72 membered) crown ethers based on isolation of the small and large cyclic polyethers made by combination of 1 mol or 2 mol each, respectively, of oligo(ethylene glycol)s and oligo(ethylene glycol) ditosylates.The advantages of this approach are the use of readily available glycols as starting materials and the ability to optimize the procedure for selective production of either macrocycle, producing yields superior or comparable to previous methods.At higher reaction temperatures the large crown ether is preferentially formed.This approach has been used to produce the crown ethers on 100-g scales.Purification was achieved by a combination of filtration through silica gel, treatment with a polymeric acid chloride, and recrystallization techniques, avoiding standard column chromatography.The pure crown ethers, 60-crown-20, 48-crown-16, 42-crown-14, 36-crown-12, and 30-crown-10, were characterized by melting points, 1H- and 13C-NMR, elemental analysis, and/or MS, GC-MS, and TGA-MS.Melting points were as much as 26 deg C higher than previously reported for these crown ethers.All the aliphatic crown ethers larger than 18-crown-6 decompose upon heating in air at ca. 200 deg C.