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

Abstract

The catalytic condensation of cis-2-butene-1,4-diol with CpRu(MQA)(C(3)H(5)) (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.

A New Strategy to Synthesize α,ω‐Dihydroxy Multiblock Copolymers via [CpRu(CH3CN)3]PF6/Quinaldic Acid Catalyst

“…Compared with PBD polymer, the 1 H NMR of MBCs (Figure S8, Supporting Information) did not find the proton at 5.26 ppm, indicating that there was no branching polyether formed during the polymerization. Therefore, combined with Waymouth's work, our result could confirm that linear enchainment for the synthesis of MBCs may play the leading role . In addition, theoretically, Ru complexes 3 and 4 could be converted into each other to achieve the growth polymerization to obtain MBCs.…”

“…Based on Kitamura's work, Waymouth et al prepared a similar catalyst named Ru allyl complex 1 (as shown in Figure ), and its kinetic process indicated that allyl ether hydrolysis was slower than the allyl ether formation using Ru allyl complex 1. Benefited with this special Ru allyl complex 1, a new polymer, poly(2‐butene‐1,4‐diol) (PBD), was successfully synthesized . This highly efficient method for the preparation of allyl ethers via allyl alcohol also offers a new strategy where the coupling reaction could be conducted in polymers possessing allyl alcohol as the terminal group.…”

“…Benefited with this special Ru allyl complex 1, a new polymer, poly(2-butene-1,4diol) (PBD), was successfully synthesized. [42,43] This highly efficient method for the preparation of allyl ethers via allyl alcohol also offers a new strategy where the coupling reaction could be conducted in polymers possessing allyl alcohol as the terminal group. However, the synthesis of complex 1, as shown in Figure 1, is complicated, and we found that complex 2 formed by [CpRu(CH 3 CN) 3 ]PF 6 /quinaldic acid shows similar catalytic activity as complex 1.…”

“…Therefore, combined with Waymouth's work, our result could confirm that linear enchainment for the synthesis of MBCs may play the leading role. [43] In addition, theoretically, Ru complexes 3 and 4 could be converted into each other to achieve the growth polymerization to obtain MBCs. However, with increasing reaction time, allyl ether hydrolysis played an important role.…”

Transition metal catalyzed nucleophilic allylic substitution: activation of allylic alcohols via π-allylic species

“…63 The catalytic oligomerisation of cis-2-butene-1,4-diol has recently been achieved in the presence of a catalyst of type 3 with 4-methoxyquinoline-2-carboxylate as the N,O-ligand (Scheme 42). 64 In this process, the allylic alcohol behaves both as the nucleophile and electrophile generator. The linear transbutenyl ethers are formed preferentially (92%) along with some vinyl branches (8%).…”