Polycondensation of Butenediol: Synthesis of Telechelic 2-Butene-1,4-diol Oligomers

The catalytic condensation of cis-2-butene- 1,4-diol withCpRu(MQA)(C3H5) (Cp =cyclopentadienyl, MQA =4-methoxyquinoline-2-carboxylate)generates poly- (2-butenediol), an unsaturated telechelic polyether diol with molecular weights between 400 and 4600 g/mol. This Ru(IV) allyl catalyst enchains 2-butene-1,4-diol primarily as the linear trans-2-butenyl ether (92%) along with vinyl branches (8%). These telechelic oligomers are useful chain extenders and macromonomers, as demonstrated by their use in the synthesis of poly(lactide)-b-poly(butenediol)- b-poly(lactide) triblock copolymers. Model studies support a proposed mechanism involving the formation of Ru(IV) allyl intermediates from allylic alcohols and chain growth by selective nucleophilic displacement at the terminus of the Ru(IV) allyl to generate trans-2-butenyl ether linkages.