Transesterification of Isosorbide with Dimethyl Carbonate Catalyzed by Task‐Specific Ionic Liquids

Abstract

Green synthesis of high‐molecular‐weight isosorbide‐based polycarbonate (PIC) with excellent properties is a tremendous challenge and is profoundly influenced by the precursor. Herein, an ecofriendly catalyst was employed to obtain the more reactive PIC precursor dicarboxymethyl isosorbide (DC) with 99.0 % selectivity through the transesterification reaction of isosorbide with dimethyl carbonate. This is the indispensable stage of a one‐pot green synthesis of PIC, playing a critical role in giving an insight into the polymerization mechanism of polymer synthesis through the melt transesterification reaction. To this end, a series of 4‐substituted phenolate ionic liquids (ILs) were developed as a new type of high‐efficiency catalyst for this reaction. These homogeneous ILs exhibited outstanding catalytic performances. The DC selectivity increased gradually with decreasing IL basicity; among the ILs studied, trihexyl(tetradecyl)phosphonium 4‐iodophenolate ([P66614][4‐I‐Phen]) showed the highest catalytic activity. Additionally, according to the experimental results and DFT calculations, a plausible nucleophilic activation mechanism was proposed, which confirmed that the reaction is activated through the formation of H‐bonds and electrostatic interactions with the IL catalyst. This strategy of tunable basicity and structure of anions in ILs affords an opportunity to develop other ILs for the transesterification reaction, thereby conveniently providing a variety of polymers through a green synthetic pathway.

Isosorbide bis(methyl carbonate) synthesis from isosorbide and dimethyl carbonate: the key role of dual basic–nucleophilic catalysts

“…This proposed reaction mechanism caused by the high activity of catalysts with a dual and suitable basic-nucleophilic character is supported by the above mentioned proposed mechanism for IBMC synthesis from ISO and DMC using 4substituted phenolate ILs as catalysts, 10 and also by other mechanisms reported in literature for other reactions. Thus, Scheme 3 Simplified proposed reaction mechanism.…”

The future of isosorbide as a fundamental constituent for polycarbonates and polyurethanes

“…Qian et al (23) designed a new type of ionic liquids with specific basicity and nucleophilic properties. They tuned the properties of the catalysts altering the basicity of the anions in the ionic liquids.…”

“…However, DPC possesses several disadvantages because is obtained from poisonous phosgene by a complicated synthetic process (23). Moreover, large amounts of toxic phenol are generated as a byproduct of the polymerization reaction of PICs (30).…”

WO3 and Ionic Liquids: A Synergic Pair for Pollutant Gas Sensing and Desulfurization

“…In addition to simple ILs, task specific ionic liquids (TSILs) must also be considered. In this case a catalytic function borne on the cation or anion structure endows the salt not only with solvent but also catalyst function [85,91,92].…”