Concepts to facilitate the conversion of epoxides with carbon dioxide to the corresponding cyclicc arbonates commonly focuso nt he activation of the epoxide.H ereinw er eport ac atalytic system which allows the simultaneous activation of carbon dioxidea nd the epoxide.T his convergent activation concept is realized by combining as uitable carbene as catalyst for the carbon dioxidea ctivation with as econd catalytic system based on potassium iodide for epoxidea ctivation.I nitial experiments showed synergistic effects andt husp roving the feasibility of this activation concept. Moreover as tandard protocol was developeda nd the substrate scope under these conditions has been studied. Under mild and solvent-free conditions 14 epoxides could be converted. Ther espective cyclic carbonates were obtained in good to excellent yields with selectivities ! 99 % after simple filtration.

X‐ray absorption: The activation of the pre‐catalyst as well as the catalytically active species and reaction mechanism of Fe‐catalyzed cross‐couplings were investigated by X‐ray absorption spectroscopy. The active catalytic components are small iron clusters with three to four FeI centers. The reaction seems to proceed by an FeI/FeIII mechanism (see figure).

Polydibenzo-18-crown-6 was utilized as a co-catalyst and polymeric support in combination with potassium iodide for the synthesis of cyclic carbonates from carbon dioxide and epoxides under mild and solvent-free conditions. The efficiency of this catalytic system can be easily increased by loading the polymer with KI prior to the reaction. The influence of various reaction parameters were studied thoroughly. The scope and limitation of the catalyst system was studied at 80 °C and 100 °C. A large number of terminal epoxides (14) were converted to the desired cyclic carbonates in yields up to 99%. We could successfully recover and reuse the catalyst >20 times with excellent yields up to 99%. Although, we observed that the activity gradually decreased after repetitive cycles. This decrease was attributed to KI leaching and partial degradation caused by mechanical stirring. This assumption is supported by scanning electron microscopy and energy dispersive X-ray spectroscopy.

A novel zinc based binary catalytic system for the synthesis of cyclic carbonates under mild and solvent-free conditions utilizing CO2as a C1 building block is reported.

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