Ring-closure reactions. Part 15. Solvent effects on cyclic aralkyl ether formation by intramolecular Williamson synthesis

Abstract

Product analysis, rate data, and effective molarity (e.m.) values have been obtained for the formation of catechol polymethylene ethers by the intramolecular alkylation of o-ω-bromoalkoxyphenoxides in Me₂SO–water (99 : 1, v/v). Twelve ring sizes were investigated in the range 6–32. Comparison with similar data for the reaction in EtOH–water (75 : 25, v/v)(except for n 32) showed that the e.m. values are largely independent of solvent despite the large solvent effect observed in both the cyclization reaction and the related intermolecular model reaction. Small effects only were observed in the medium ring region. The main possible factors playing a role in solvent effects on intramolecular cyclization have been critically analysed in the light of the data.