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Download fileCalcium-Based Catalytic System for the Synthesis of Bio-Derived Cyclic Carbonates under Mild Conditions
journal contribution
posted on 2017-12-05, 00:00 authored by Lars Longwitz, Johannes Steinbauer, Anke Spannenberg, Thomas WernerRecently,
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.
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dicyclohexyl-functionalized 18- crown -6 ethertriphenylphosphaneyieldcalcium-based catalyst systemDBU1 H NMR spectroscopybio-derived cyclic carbonatesCO 2trisubstituted cyclic carbonatescocatalystTBDreaction conditionsSeveral crown ethersBio-Derived Cyclic Carbonatesbio-derived epoxidesNIPU0.5 MPa CO 2 pressureCalcium-Based Catalytic System