ABSTRACT
Herein the use of CaI2 in combination with poly(ethylene glycol) dimethyl ether (PEGâ DMEâ 500) as an efficient catalyst system for the addition of CO2 to epoxides is reported. This protocol is based on a nontoxic and abundant metal in conjunction with a polymeric ligand. Fifteen terminal epoxides were converted at room temperature to give the desired products in yields up to 99 %. Notably, this system was also effective for the synthesis of twelve challenging internal carbonates in yields up to 98 %.
Subject(s)
Calcium/chemistry , Carbonates/chemistry , Carbonates/chemical synthesis , Ethers/chemistry , Polyethylene Glycols/chemistry , Catalysis , Chemistry Techniques, Synthetic , LigandsABSTRACT
The use of CO2 as a C1 building block will be of essential importance in the future. In this context the synthesis of cyclic carbonates from epoxides and CO2 gained great attention recently. These products are valuable compounds in a variety of chemical fields. The development of new catalysts and catalytic systems for this atom-economic, scalable, and industrially relevant reaction is a highly active research field. Over the past 17 years great advances have been made in this area of research. This chapter covers the survey of the important known classes of homogeneous catalysts for the addition of CO2 to epoxides. Besides pioneering work, recent developments and procedures that allow this transformation under mild reaction conditions (reaction temperatures of ≤100 °C and/or CO2 pressures of 0.1 MPa) are especially emphasized.
Subject(s)
Carbon Dioxide/chemistry , Carbonates/chemical synthesis , Epoxy Compounds/chemistry , Carbonates/chemistryABSTRACT
Bifunctional phosphorus-based organocatalysts proved to be highly efficient for the atom-economic reaction of CO2 and epoxidized oleochemicals. Notably, those products are obtained from CO2 and renewable feedstocks only. Structure-activity relationships have been deduced from a screening of 22 organocatalysts in a test reaction. Bifunctional catalysts based on a phosphonium salt bearing a simple phenolic moiety proved to be extraordinarily active under comparatively mild and solvent-free reaction conditions. In the presence of the most active organocatalyst 12 oleochemical carbonates were isolated in excellent yields up to 99 %. This organocatalyzed reaction represents an excellent example for the realization of the 12 Principles of Green Chemistry as well as the 12 Principles of CO2 Chemistry.
Subject(s)
Carbon Dioxide/chemistry , Carbonates/chemistry , Fatty Acids/chemistry , Fatty Acids/chemical synthesis , Catalysis , Chemistry Techniques, Synthetic , Epoxy Compounds/chemistry , Green Chemistry TechnologyABSTRACT
Numerous bifunctional organocatalysts were synthesized and tested for the atom-efficient addition of carbon dioxide and epoxides to produce cyclic carbonates. These catalysts are based on phosphonium salts containing an alcohol moiety in the side chain for substrate activation through hydrogen bonding. In the model reaction, converting 1,2-butylene oxide with CO2 , 19 catalysts were tested to determine structure-activity relationships. In total, 28 epoxides were converted with CO2 to give the respective cyclic carbonates in yields of up to 99%. Even at 45 °C, the most active catalyst was able to produce cyclic carbonates selectively in high yields. The carbonates were generally obtained as analytically pure products after simple filtration over silica gel. This single-component catalyst system works under neat and mild reaction conditions and tolerates several useful moieties.
