| Abstrakt: |
A series of dopamine‐based mono‐ and dinuclear boronate esters are studied as stable, efficient, and green metal‐free catalysts for coupling CO2with epoxides under suitable and solvent‐free conditions. Under the optimized reaction conditions, dinuclear boronate esters compared with those with mononuclear compounds display high catalytic activity and selectivity for the chemical conversion of CO2into cyclic organic carbonates as a valuable product. Ferrocene group containing boronate ester (B4a) display the highest activity for the carboxylation of epichlorohydrin at 100 °C and 1.6 MPa of CO2pressure, obtaining 96.3% conversion after just 2 h. After seeing a high catalytic performance of trigonal‐planar boronate ester (B1–B5) and tetrahedral boronate ester (B1a–B5a) catalysts, the effect of ionic liquid, epoxide, base, temperature, CO2pressure, reaction time, and amount of catalyst/substrate/cocatalyst is investigated for these catalysts. The newly synthesized dopamine‐based trigonal‐planar and tetrahedral boronate esters are entirely characterized by melting point, elemental analysis, NMR (1H, 13C, and 11B NMR) spectroscopy, FT‐IR spectroscopy, UV–vis spectroscopy, and LC–MS/MS spectrometry. The novel boronate esters are synthesized and characterized by melting point, elemental analysis, NMR spectroscopy, FT‐IR spectroscopy, UV–vis spectroscopy, and LC–MS/MS spectrometry. The comparison of different types of boron catalysts for reactions in CO2fixation is presented. A conversion of 96.3% is observed using boronate ester catalyst and also the different catalytic parameters are investigated in this study. |
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