Chlorodimethylsilane-Mediated Reductive Etherification Reaction: A Robust Method for Polyether Synthesis

Abstract

Polyethers have always been privileged compounds in polymer chemistry and have found extensive applications in both academic research and industry. However, the currently employed strategies for their synthesis require harsh conditions such as ionic polymerizations together with limited precursor monomer options. In this study, a chlorodimethylsilane (CDMS)-mediated reductive etherification reaction was introduced as a versatile strategy for polyether synthesis. Accordingly, terephthalaldehyde (TPA) and 1,4-butanediol were first reacted at room temperature in the presence of CDMS using nitromethane as the polymerization solvent to reveal the optimum conditions for the proposed system. Subsequently, a variety of diols ranging from linear to sterically congested diols were reacted with TPA (and its isomers) under the optimized conditions to create a polyether library. Meanwhile, in addition to polyether having the expected alternating units, the formation of polyether stem from the self-condensation of TPA was found to be inevitable in all cases. From the proposed strategy, polyethers with a molecular weight of up to 110.4 kDa and a high alternating unit of up to 93% were obtained. The versatile and robust character of the presented strategy was supported by a model end-group study, and the polymerization behavior was examined mechanistically. It is anticipated that the presented method might be a strong candidate for polyether synthesis with different backbones, given the unlimited sources of diols.

Polyether Synthesis through Reductive Etherification Reaction Strategy

“…The polycondensation was accomplished using terephthaldehyde (TPA) and 1,4‐butanediol (BD) with CDMS in CH 3 NO 2 at room temperature ( Scheme ). [ 73 ] Therefore, a toolbox of polyethers was created utilizing a variety of diols (linear to bulky) and TPA (and its isomers) under the optimum reaction conditions. The plausible mechanism for the CDMS‐based RER for polyether synthesis with alternating units is as follows ( Scheme A).…”

“…The formation of polyethers owing to the self‐condensation of TPA seems to be unavoidable besides the polyether with alternating units in all conditions (see related Scheme 7B). [ 73 ] Nevertheless, polyethers containing alternating units ranging from 73% to 93% were achieved with low (3 kDa) to high (110.4 kDa) molecular weights. It should be pointed out that dissimilar to the preparation of polyethers based on the RER mechanism that needs the protected alcohols before the polymerization, the CDMS‐based RER for the polyether synthesis may display an advantageous position, avoiding the extra reaction step for protection.…”

Recent Developments in Catalytic Reductive Etherifications

“…Besides that, the etherification of furanic chemicals generated from biomass to produce biofuel has a variety of uses as fuel additives [3,18,19]. Biomass with wide precursors and the richest and most diverse natural carbon source can be used to produce green products like biofuels or alternative additives without having an impact on human food consumption [12]. An acid catalyst is also necessary for the etherification of furanyl alcohol to proceed.…”

“…Aldehydes are acetalized during the reductive-etherification process as an intermediate step, and the final ethers are created by hydrogenation of the (partial) acetal through hydrogenolysis and dehydration, due to a lack of acid sites, the side-product production of alcohol reduced the ether yield [10,11]. The reductive etherification reaction is a simple way to generate either symmetric or asymmetric ether by the coupling reaction with aldehyde ketone with uses a lewis acid, Brönsted acid, and metal catalyst of various types and also can be conveniently performed using a catalyst [4,12] The parameters such as solvents and reactant amounts affected on reductive etherification reaction [13], and polymers of a modest molecular weight were formed in yields ranging from low to high. The development of the related reductive etherification reactions, however, has not yet developed to their full potential [1,14].…”

Poly(silyl ether)s (silyl ether copolymers) via hydrosilylation of carbonyl compounds

“…In the RER protocol, carbonyl compounds in the presence of silane and a Brønsted or Lewis acid catalyst afford the synthesis of symmetric and unsymmetrical ethers. 8–28 However, the silyl ether is produced rather than the corresponding ether in the hydrosilylation. Notably, both mechanisms seem to cover the competing reaction pathways.…”