Use of Polyoxetane Resin-Supported Quaternary Onium Salts as a Polymeric Phase-Transfer Catalyst for Preparing Ethers from Hydroxy Compounds and Alkyl Halides

As a polymer support for preparing polymeric phase-transfer catalysts (PTC), soft, moderately polar polyoxetane resins were employed which were synthesized by a cationic ring-opening copolymerization of oxetanes Br(CH2)nOCH2–X with bisoxetanes X–CH2O(CH2)nOCH2–X, where X=3-methyl-3-oxetanyl and n=4 or 6. In a few cases of those polymerizations, 3-(2-oxadecyl)-3-methyloxetane was used as a comonomer with a lipophilic pendant. The terminal bromine of the pendant groups of such polyoxetane resins was quaternized with tributylamine or tributylphosphine in DMF in order to examine the phase-transfer catalyzing ability of the resultant quaternary onium bromides in the etherification reaction between alkyl halides and alcohols or phenols. These reactions gave the desired products in fairly good yields within reaction periods of 1–3 h, indicating that the catalytic activities of those PTCs are comparable to that of tetrabutylammonium bromide. A fairly high catalytic activity of the polymeric PTC was observed at each of ten stages in a process using the polymeric PTC repeatedly for the etherification reaction of 3-hydroxymethyl-3-methyloxetane with 1,4-dibromobutane.