The Synthesis and polymerization of oxo-crown ethers

A novel synthetic route to and a polymn. procedure for oxo-crown ethers 2,11-dioxo-18-crown-6 (I), 2-oxo-12-crown-4 (II), and 2-oxo-21-crown-7 (III) are described. Cyclization, of the w-hydroxycarboxylic acid precursors of I-III was achieved by heating these precursors in the presence of a Lewis acid catalyst (CoCl2) and template salt (MCl). Cyclization yields ?82% were reached, using CsCl as template salt. Oxo-crown ethers I-III were polymd. using SnOct2 as catalyst, giving polymers with mol. wts. of approx. 5 kg/mol and dispersities of ca. 1.8 (measured with polyethylene oxide stds.). The polymn. of II was monitored with 1H-NMR and SEC giving information about the influence of monomer/catalyst ratio and temp. on polymn. rate as well as the influence of temp. on mol. wt. (distribution). The possibility of introducing end groups into II homopolymer using SnOct2-catalyzed polymn. was also studied