Synthesis of functionalized polyethers by ring-opening metathesis polymerization of unsaturated crown ethers

A variety of polyethers were synthesized by a tandem approach incorporating ring-closing metathesis (RCM) followed by ring-opening metathesis polymerization (ROMP) using RuCl2(=CHPh)-(PCy3)(2) (1) as an initiator. Unsaturated crown ether monomers, including a 12-crown-4 analogue (3), a benzocrown ether (8), and a benzocrown ether with a pendent phenylalanine methyl ester (9), were synthesized in good yields using a lithium ion as a template and 1 as a catalyst for RCM. Saponification of 9 afforded the benzocrown phenylalanine carboxylic acid monomer 10. The ROMP of 3, 8, and 9 with 1 as an initiator yielded the homopolymers 11, 12e, and 13e, respectively. The relative concentrations of 3 to 1 were varied to produce 11 with a wide range of molecular weights (M-n from 10 900 to 206 300). Hydrogenation of 11 proceeded quantitatively to yield a saturated polyether. Monomers 8 and 9 were copolymerized with 3 to generate polymers 12a-d and 13a-d, respectively. The copolymer composition corresponded to the feed ratio of the monomers. Crown ether 10 was copolymerized with 3 at a low feed ratio to form the corresponding polyether with pendent amino acids.