Synthesis of cyclic carbonates from CO₂and epoxides catalyzed by low loadings of benzyl bromide/DMF at ambient pressure

Abstract

An efficient, metal-free catalytic system for the conversion of CO2 and epoxides to cyclic carbonates under mild conditions with good-to-excellent yields (57-99%) was developed. A possible reaction mechanism involving the electrophilic activation of epoxides by benzyl cations and nucleophilic activation of CO2 by DMF is proposed.

Carbon Dioxide Based N‐Formylation of Amines Catalyzed by Fluoride and Hydroxide Anions

“…A positive solvent effect was observed in DMF, and the reaction rate was greatly enhanced (Table , entry 15). DMF has been demonstrated to activate hydrosilanes and more recently was proposed to activate CO 2 by interacting with the electrophilic carbon center . However, although these mechanisms could partially account for the higher activity, in the presence of far superior nucleophiles, that is, F − or OH − anions, such mechanisms seem less likely to improve significantly the reaction rate.…”

“…DMF has been demonstrated to activate hydrosilanes [26] and more recently was proposed to activate CO 2 by interacting with the electrophilic carbon center. [27] However,a lthought hese mechanismsc ould partially account for the higher activity,i nt he presence of far superior nucleophiles, that is, F À or OH À anions, such mechanisms seem less likely to improves ignificantly the reaction rate. Moreover,t he effect cannotb ea ttributed to enhanced homogenization of the system,a sT BAF completelyd issolves in all of the aforementioned solvents.…”

Poly(4‐vinylphenol)/tetra‐n‐butylammonium iodide: Efficient organocatalytic system for synthesis of cyclic carbonates from CO2 and epoxides

“…The yield decreased by a factor of 0.5 in the order I − (99%) > Br − (49%) > Cl − (25%) when these binary catalyst systems were used (Table , Entries 8 and 9 vs. Entry 2), as has often been reported . Considering that the intrinsic activity and nucleophilicity increase in the order Cl − > Br − > I − , the results are often interpreted through the leaving ability of the halide ion, which decreases in the order I − > Br − > Cl − .…”

“…From the perspectives of “green chemistry” and “sustainable society,” high pressure/temperature, organic solvent, and metal waste should be reduced by applying metal‐free catalysts and benign reaction conditions . Thus far, numerous catalysts, including homogeneous and heterogeneous ones, have been developed for CO 2 conversion reactions. Especially organocatalysis is attracting increasing attention from the viewpoint of reducing the amounts of metal residues in end products.…”

Novel porous organocatalysts for cycloaddition of CO2and epoxides

“…The contact time and recycling delays were set at 10 ms and 2 s for 13 C NMR respectively. For 29 Si NMR, the contact time and recycling delays were set at 2 ms and 1.5 s. For solution NMR measurements, 13 C and 1 H NMR spectra were obtained using a Bruker AV 400 MHz spectrometer. Chemical shis are reported in ppm relative to deuterated chloroform.…”