Polyethers as Complexing Agents in Calcium-Catalyzed Cyclic Carbonate Synthesis

Abstract

Herein, we report a detailed investigation of alkali and alkaline earth metal salts in combination with polyethers as catalytic systems for the synthesis of cyclic carbonates from epoxides and CO2. CaI2 showed superior activity compared to various other tested alkali and alkaline earth metal salts. Interestingly, in contrast to other catalytic protocols, the presence of hydroxyl groups hampered the reaction. Thus, poly­(ethylene glycol) dimethyl ethers (PEG DME) proved to be the most suitable polymer complexing agents. This catalytic protocol is based on a nontoxic and abundant metal as well as readily available polymer coordination agents. Notably, 26 terminal epoxides were converted even at room temperature with CO2 to the corresponding cyclic carbonates in yields up to 99%. Additionally, this system was also effective for the synthesis of 21 challenging internal carbonates based on fossil and renewable feedstock in yields up to 98%. Significantly, at a large scale, namely, 10 g of epoxide, a quantitative yield of cyclic carbonate was isolated in the presence of only 1 mol % catalyst under ambient conditions. Two different recycling strategies were tested which allowed the reuse of the catalyst up to 7 times without the loss of activity.

Catalytic Formation of Cyclic Carbonates using Gallium Aminotrisphenolate Compounds and Comparison to their Aluminium Congeners: A Combined Experimental and Computational Study

“…Finally, an epoxide based on dicyclopentadiene was successfully converted to the corresponding cyclic carbonate where only one of the epoxides is selectively converted (Table 3, 24 b ). This selectivity has previously been observed by the few groups that have attempted conversion of this challenging substrate [5b,20,29,30] . In summary, increasing the reaction temperature, allows for the successful conversion of more complex substrates.…”

Recent progress in the catalytic transformation of carbon dioxide into biosourced organic carbonates

“…Whereas most coordination compounds of calcium are generally insoluble in most reaction media, Werner et al showed that the use of chelating ligands (crown ethers) in combination with calcium halides leads to soluble and highly active Lewis acids for CO 2 /epoxide cycloaddition. 118,209,[280][281][282] The in situ complexation of CaI 2 by poly(ethylene glycol)dimethyl ether (PEG-DME-500) further promotes the nucleophilicity of the iodide anion leading to a system able to mediate the cycloaddition of CO 2 to terminal and internal epoxides including iEFA1 (entry 4, Table 6). 280 Alternatively, crown ethers are effective complexing agents for CaI 2 leading to highly active calcium catalysts such as 4 for the cycloaddition of CO 2 to terminal epoxides under ambient conditions.…”

Synthesis of Bio‐Based Cyclic Carbonates Using a Bio‐Based Hydrogen Bond Donor: Application of Ascorbic Acid to the Cycloaddition of CO2 to Oleochemicals

“…Addition of metal‐based Lewis acidic complexes to nucleophilic quaternary salts has the effect to strongly accelerate carbonation of internal epoxides; Fe(II) bispincer‐type, V(V) and Al(III) aminotriphenolate complexes were reported to promote the carbonation of epoxidized methyl oleate (EMO) in the 70–100 °C temperature range under 5–10 bar CO 2 in presence of nucleophilic halide salts. Use of CaI 2 /PPh 3 /dicyclohexyl‐functionalized 18‐crown‐6 ether (DCFCE) led to carbonation of EMO at low temperature (45 °C) under 10 bar CO 2 pressure . Similarly, efficient Al(III) and La(III) complexes were reported as Lewis acids for carbonation of limonene monoxide under mild conditions (70–85 °C, 10 bar CO 2 ).…”