Renewable Polyethers via GaBr₃‐Catalyzed Reduction of Polyesters

Abstract

Herein, a novel approach is reported for the synthesis of medium- and long-chain aliphatic polyethers 2 based on the GaBr -catalysed reduction of polyesters 1 with TMDS as the reducing agent. Thus, various linear and branched aliphatic polyesters 1 were prepared and systematically investigated for this reduction strategy, demonstrating the applicability and versatility of this new polyether synthesis protocol. Medium- and long-chain chain polyethers were obtained from the respective polyesters without or with minor chain degradation, whereas short-chain polyesters, such as poly-l-lactide 1 i and poly[(R)-3-hydroxybutanoate] 1 j, showed major chain degradation. In this way, previously unavailable and uncommon polyethers were obtained and studied.

Fatty Acid–Derived Aliphatic Long Chain Polyethers by a Combination of Catalytic Ester Reduction and ADMET or Thiol‐Ene Polymerization

“…The relative increase ranging from 24 to 44 °C is higher for shorter monomers. Overall, the general range of the melting point of this aliphatic polyethers is comparable to results we obtained by a direct reduction of polyesters to polyethers . For example, hydrogenated polyether P3e with alternating C18/C20 segments between the ether groups ( T m = 99.8 °C) is indeed similar to the statistical C17/C21 polyether 2e in the literature .…”

“…[13] For example, hydrogenated polyether P3e with alternating C18/C20 segments between the ether groups (T m = 99.8 °C) is indeed similar to the statistical C17/ C21 polyether 2e in the literature. [13] (T m = 96.6 °C).…”

“…1 H NMR (CDCl 3 , 300 MHz): δ (ppm) = 5.80 (ddt, J = 16.9, 10.2, 6.7 Hz, 1H, CHCH 2 ), 5.07-4.83 (m, 2H, CHCH 2 ), 3.66 (s, 3H, COOCH 3 ), 2.30 (t, J = 7.5 Hz, 2H, CH 2 COO), 2.13-1.93 (m, 2H, CH 2 CHCH 2 ), 1.74-1.48 (m, 2H, CH 2 CH 2 COO), 1.46-1. 19 (m, 8H, CH 2 ); 13 C-NMR (CDCl 3 , 75 MHz): δ (ppm) = 174.2 (C = O), 139.0 (CHCH 2 ), 114.19 (CHCH 2 ), 51.4 (H 3 COOC), 34.1 (CH 2 COO), 33.8 (CHCH 2 ), 29.1 (CH 2 ), 28.9 (CH 2 ), 24.9 (CH 2 CH 2 COO); HRMS (EI) C 11…”

“…ω,ω′-Diether M2b was separated by "Kugelrohr" distillation (180 °C, 1 × 10 −3 mbar) to give 5.14 g (75%) of the pure product. 1 H NMR (500.1 MHz, CDCl 3 ): δ (ppm) = 5.73 (ddt, J = 17.1, 10.3, 6.7 Hz, 2 H, CHCH 2 ), 4.91 (dd, J = 17.1, 1.9 Hz, 2 H, CHCH a H b ), 4.84 (dd, J = 10.3, 1.9 Hz, 2 H, CHCH a H b ), 3.43 (t, J = 6.5 Hz, 4H, OCH 2 ), 3.32 (t, J = 6.7 Hz, 4 H, OCH 2 ), 1.96 (dt, J = 7.2, 6.7 Hz, 4H, CH 2 CHCH 2 ), 1.76 (tt, J = 6.5, 6.3 Hz, 2H, OCH 2 CH 2 CH 2 O), 1.49-1.44 (m, 4H, CH 2 CH 2 O), 1.33-1.25 (m, 4H, CH 2 ), 1.25-1.17 (m, 20H, CH 2 ); 13…”

“…[12] Additionally, we recently demonstrated that this catalytic method can be used to directly reduce poly esters to polyethers, obtaining structurally simple, yet to since recently unknown polyethers. [13] Here, we expand the concept of catalytic ester reduction for polymer synthesis to a set of six different ω,ω′-unsaturated ether monomers, which were obtained from fatty acid-derived raw materials. In comparison to previous publications on ADMET and thiol-ene polymerizations of fatty acid-derived substrates, [2,7,8,11,[14][15][16] of which only very few discuss ether monomers, [2,11] here we describe a broader spectrum of monomers.…”