Calcium-Based Catalytic System for the Synthesis of Bio-Derived Cyclic Carbonates under Mild Conditions

Abstract

Recently, bio-derived cyclic carbonates have gained significant importance: e.g., as building blocks in non-isocyanate polyurethanes (NIPUs). Herein we report the development of a calcium-based catalyst system for the synthesis of challenging internal and trisubstituted cyclic carbonates from bio-derived epoxides and CO2 under mild reaction conditions. Several crown ethers were tested as ligands in combination with various cocatalysts for the possible activation of CO2. The most active system consists of a dicyclohexyl-functionalized 18-crown-6 ether and triphenylphosphane in addition to calcium iodide. The in situ complexation of Ca2+ by the crown ether was detected by 1H NMR spectroscopy. Interestingly, the addition of triphenylphosphane as a cocatalyst leads to a significant increase in activity, which is similar to or even higher than that of organic superbases such as DBU and TBD. The catalytic system was employed in the conversion of 16 different bio-derived epoxides, including fatty acid esters, oils, and terpenes with CO2, and is able to facilitate the reaction under mild conditions. Various internal epoxides were converted at only 45 °C, 0.5 MPa CO2 pressure, a catalyst loading of 5 mol %, and a reaction time of 24 h with isolated yields up to 98% of the respective carbonate. The challenging terpene-based carbonates were isolated in yields up to 81%, although harsher reaction conditions were necessary.

Ionic‐Liquid‐Functionalized UiO‐66 Framework: An Experimental and Theoretical Study on the Cycloaddition of CO2 and Epoxides

“…[2,3] Compared to carbon capture and storage( CCS) techniques, carbon capturea nd utilization (CCU) techniques are more attractive, ast he captured CO 2 can be effectively converted to various valuable productss uch as urethanes, formic acid, dimethyl carbonate, and cyclic carbonates. [11][12][13][14][15][16][17][18][19][20] Cyclic carbonates are highly stable compounds; thus, long-term sequestration of CO 2 is possible. [11][12][13][14][15][16][17][18][19][20] Cyclic carbonates are highly stable compounds; thus, long-term sequestration of CO 2 is possible.…”

Polymers Based on Cyclic Carbonates as Trait d'Union Between Polymer Chemistry and Sustainable CO2 Utilization

“…[1c] Unfunctionalized saturated carbonates can be used for the synthesis of polymers by nucleophilic ring opening with diamines leading to bis-hydroxycarbamates as starting materials for isocyanatefree polyester polyurethanes. [53] 1c can be formed asab yproduct of back-biting in CHO/CO 2 copolymerization. In general,p olymers with relativelyl ow molecular weights wereo btained at high temperature with partial loss of CO 2 .…”

“…[211] Improvement of the keyc atalytic step of CO 2 cycloaddition to the epoxide precursors is another viable strategy to further enhancet he sustainability of 5CCs. Additionally,e fficient Lewis acids have emerged for the insertion of CO 2 into internal epoxides.F or instance, the organometallic complexes shown in Scheme 24 allow the efficient carbonation of internal epoxides such as limonene (7a, 9) [65a, 164] and epoxidized fatty acids (7b, 8) [53,214] at moderateC O 2 pressures. [212] These compounds generallyr equire temperatures around1 00 8C, pressures in the 20-40 bar range, and polar solvents such as DMF or NMP (for LiBr), leadingt om ore demanding purification procedures and to the production of chemical wastes.…”

“…Thes ynthesis of pure 1c (racemic or chiral) from CO 2 is challenging because cyclohexene oxide (CHO) is a meso-epoxide [52] and the cycloadditiono f CO 2 to epoxides generallyp roceeds with retention of configuration. [53] 1c can be formed asab yproduct of back-biting in CHO/CO 2 copolymerization. [54] cis-CHC, instead, can be prepared selectively.…”

Cobalt‐based catalytic system for the chemical fixation of CO2 under solvent‐free conditions

“…As a continuation of our study on using ligands for enhancing the coupling reaction, and encouraged by the Werner group's work, which depicted that catalyst system ‘CaI 2 /L1’ (or ‘CaI 2 /18‐crown‐6’) could be used for the synthesis of cyclic carbonates from epoxides and CO 2 (Scheme , a and b), we tried the reaction in the presence of different ligands, and found that the combination of ‘CoNO 3 . 6H 2 O/L2’ could efficiently promote the coupling reaction of CO 2 and epoxides in solvent‐free reactions (Scheme , c).…”