Ionic cyclic carbonates

Han, L., et al., Ionic liquids grafted on carbon nanotubes as highly efficient heterogeneous catalysts for the synthesis of cyclic carbonates. Applied Catalysis A General, 2012. 429-430(0) p. 67-72. 

Kim, Y. J. and Varma, R. S., Tetrahaloindate(III)-based ionic liquids in the coupling reaction of carbon dioxide and epoxides to generate cyclic carbonates H-bonding and mechanistic studies, /. Org. Chem., 70, 7882,2005. 

Synthesis of Linear and Cyclic Carbonates 7.3.1.2 Use of Ionic Liquids... 

Dunach, Inesi and others also investigated the electrochemical synthesis of cyclic carbonates from C02 with epoxides, alcohols and glycols [66]. In this regard, Yang et al. [67] reported the use of pure room temperature ionic liquids (ILs) as reaction media in the electrochemical activation of C02 for the synthesis of cyclic carbonate from epoxide, under mild conditions. C02-saturated IL (BMIMBF4) solutions were also used for the electrochemical carboxylation of activated olefins [68]. Monocarboxylic acids were obtained in moderate yield (35-55%), and the IL was recycled five times. 

Poly(bisphenol-A-carbonate) under pseudoideal reaction conditions was investigated, and the cyclic polycarbonate was obtained as the main product. In the system, the interface of the water/toluene mixture might have favored the cyclization reaction between the polar end groups [88]. Cyclic carbonates during the (Salen)CrCl catalyzed CCh/cyclohexene oxide copolymerization process in the presence of ionic initiators was also obtained [89]. The cyclic carbonate is produced via the backbiting mechanism, and the process is assumed to take place via a metal alkoxide (polymer chain) intermediate. Subsequent ring-opening of the cyclic carbonate with concomitant formation of polyether and CO2 was fast at the reaction temperatures from 80 to 100 °C). 

Dharman MM, Choi H-J, Kim D-W et al (2011) Synthesis of cyclic carbonate through microwave irradiation using silica-supported ionic liquids Effect of variation in the silica support. Catal Today 164(1) 544—547... 

Scheme 5.5 Structures of PEG-functionalized ionic liquids for the synthesis of cyclic carbonates. Reproduced from Ref. [15] by permission of The Royal Society of Chemistry...

Yang ZZ, He LN, Miao CX et al (2010) Lewis basic ionic liquids-catalyzed conversion of carbon dioxide to cyclic carbonates. Adv Synth Catal 352(13) 2233-2240... 

An enormous variety of r-bonded systems, whether they be neutral or ionic, cyclic or linear, odd or even in the number of carbon atoms, serve as ligands that coordinate to transition metals. Figure 14.3.1 shows some representatives of the innumerable organometallic coordination compounds stabilized by metal-TT bonding. 

It may be mentioned that the use of ionic nucleophilic initiators, instead of zinc-based coordination catalysts, in order to promote propylene oxide/carbon dioxide copolymerisation, did not result in the formation of any copolymer but led to the cyclic carbonate, propylene carbonate [194,236,237]. Also, zinc-based coordination catalysts with non-condensed zinc atoms in their molecules (formed by the reaction of diethylzinc with a monoprotic compound such as... 

Zhu Z, Einset A G, Yang Ch-Y et al. (1994) Synthesis of PolysUoxanes Bearing Cyclic Carbonate Side Chains. Dielectric Properties and Ionic Conductivities of Lithium Triflate Complexes. Macromolecules 27 4076-4079. 

Deng and his coworkers found that CO2 was reduced at a cupper cathode at —2.4 V vs. Ag/AgCl [42]. They successfully prepared cyclic carbonates by the reduction of CO2 in the presence of epoxides in various ionic liquids like [EMIM][BF4], [BMIMJiPFg], and A-butylpyridinium tetrafluoroborate [BPy][BF4] using a Cu cathode and Mg or A1 anode as shown in Scheme 8.16. This electrolysis is nonfaradaic reaction in which a small amount of electricity engaged in the electroreduction of CO2 generates catalytic species responsible for the addition of CO2 to epoxides to form cyclic carbonates. 

Higher-chlorinated camphenes are the most plausible side products. They may be formed together with other cyclic carbon skeletons if the Wagner-Meerwein rearrangement (to polychlorinated bornanes) is hindered [38, 39]. The ionic addition of chlorine to the primary olefinic carbon is always in competition with radical chlorination. Although the first mechanism is more likely, the second one may also take place. It was found that a gentle chlorination of... 

The synthesis of cyclic carbonates in RTILs, via cycloaddition of cathodically activated carbon dioxide to epoxide, has been reported by Deng et al. [139]. Ionic liquids, saturated with CO by bubbling at normal pressure and containing the epoxidic substrate, were electrolyzed in an undivided cell (Cu as cathode. Mg or Al as sacrificial anode). The electrolyses were carried out under potentiostatic conditions at a potential negative enough to the selective reduction of CO to CO (E=-2.4 V vs. 

Yang H, Gu Y, Deng Y, Shi F (2002) Electrochemical activation of carbon dioxide in ionic liquid synthesis of cyclic carbonates at mild reaction conditions. Chem Commun 3 274-275... 

A tetrahalideindate(III)-based ionic liquid has recently been used as a recyclable catalyst in the coupling of carbon dioxide and epoxides to provide ready access to cyclic carbonates (Scheme 8.95) [240]. Mechanistic details have been described. 

Silica grafted imidazolium-based ionic liquids efficient heterogeneous catalysts for chemical fixation of COj to a cyclic carbonate. Energy Environ. Sci.,... 

Cyclic carbonates are prepared by the reduction of CO2 at —2.4 V versus Ag/AgCl in the presence of epoxides in various ionic liquids like [EMIM]... 

The catalytic activity of phosphonium salts in the synthesis of cyclic carbonates (e.g., propylene carbonate from propylene oxide and carbon dioxide) was found to be greatly enhanced by their immobilization onto silica that itself had no catalytic effect. The discipline of ionic liquids keeps developing dynamically. Phosphonium ionic liquids have received much less attention than ammonium salts in the past, but the situation is changing. Triphenylalkyl-, tetraalkyl- and functionalized-phospho-nium tosylates (Fig. 11) that exhibit melting points mostly above 100 °C were introduced and characterized. 

The synthesis of cycUc carbonates from epoxides and CO2 (Scheme 1) is one of the major ways to transform CO2 to valuable chemicals. The first successful synthesis of cyclic carbonate using room temperature ILs of imidazolium and pyridinium salts was reported by Peng and Deng in 2001 [9]. It has been shown that cycloaddition of CO2 to propylene oxide (PO) producing propylene carbonate (PC) is effectively catalyzed by [BMIm]BF4. PO was quantitatively converted to PC with 2.5 MPa of CO2 at 110°C for 6 h in the presence of 2.5 mol% [BMIm]BF4. After the reaction, PC was distilled from the reaction mixture and the catalyst was recycled up to four times with only a minor loss in activity. The ionic liquid catalyst is recyclable for the cycloaddition of CO2 to PO. They also showed that the type of either cation or anion affect the activity of the ILs. The activity decreased in the orders of [BMIm]+ > [BPy]+ and of BF4 > Cl > PFe". 

I have also included in this book the insertion reactions of carbon cumulenes into polarized metal single bonds, which can be perceived as an initial [2+2] cycloaddition, which subsequently rearranges to give a linear adduct. The reactivity of the metal substituent appears to be NR2 > OR > SR. When the metal compound contains several reactive groups, stepwise insertion occurs. For example, Sn(OR)4 reacts with phenyl isocyanate to give the tetracarbamate Sn[N(Ph)COOR]4. Mixed insertion products are obtained using different isocyanates. In the insertion reactions of carbodiimides sometimes ionic cyclic amidinate complexes are formed. 

Higher yields of cyclic carbonates are obtained using chromium (iii) bis(salicylaldimine) complexes in combination with DMPA as a catalyst. Also, tetrahaloindate (m) based ionic liquids catalyze this reaction. From chloromethyloxirane and CO2 (7 bar) at 120 °C a 98 % yield of the corresponding carbonate is obtained . 

Miscellaneous Reactions. Ionic liquids are known to promote fixation of carbon dioxide to propargyl alcohols under copper(I) chloride catalysis to give a-methylene cyclic carbonates (eq 66) or 5-methylene-l,3-oxazolidin-2-ones in excellent yields (eq 67)3 ... 

Chemical fixation of carbon dioxide with oxiranes to form cyclic carbonates proceeds very effectively under mild conditions using immobilized ionic liquid (IL) catalyst in conjunction with zinc chloride without any organic solvents. The optimum reaction conditions were 110 °C and 1.5 MPa, and the catalyst system was recycled and reused.The reaction of carbon dioxide with oxiranes can be catalyzed by typical ILs (1 -alkylmethylimidazolium salts) 7 ... 

Thus, instead of using ionic and coordination initiators it is possible to use organic initiators for the polymerization of six-membered cyclic carbonates. Murayama et have... 

Ionic liquids have also been found to be efficient reaction media for the activation of CO2 [82-84]. Diurea derivatives are easily obtained from amines and carbon dioxide with a CsOH/ionic liquid catalyst system [83]. N-Substituted 4-methylene-2-oxazolidinones are also efficiently synthesized in IL media by reaction of carbon dioxide with propargylic alcohol and different amines [82]. Other examples include the cycloaddition of CO2 to epoxides to produce cyclic carbonates [85] and synthesis of cyclic urethanes [86,87]. 

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