Carbonates, cyclic epoxides

Ni(cyclam)]2+ was shown to be an efficient electrocatalyst for the intramolecular cyclization-carboxylation of allyl or propargyl-2-haloaryl ethers,200 and for the synthesis of cyclic carbonates from epoxides and carbon dioxide.201... 

Silica gel-based catalytic systems have been described as efficient promoters for a number of organic reactions.28 Illustrative examples include the oxidative cleavage of double bonds catalyzed by silica-supported KM11O4,29 reaction of epoxides with lithium halides to give /i-halohydrins performed on silica gel,30 selective deprotection of terf-butyldimethylsilyl ethers catalyzed by silica gel-supported phosphomolybdic acid (PMA),31 and synthesis of cyclic carbonates from epoxides and carbon dioxide over silica-supported quaternary ammonium salts.32... 

J.-Q. Wang, D.-L. Kong, J.-Y. Chen, F. Cai, and L.-N. He, Synthesis of cyclic carbonates from epoxides and carbon dioxide over silica-supported quaternary ammonium salts under supercritical conditions, /. Mol. Cat. A Chem., 249 (2006) 143-148. 

Not least for the syntheses of natural products, alkoxycarbonylations with formation of allenic esters, often starting from mesylates or carbonates of type 89, are of great importance [35, 137]. In the case of carbonates, the formation of the products 96 occurs by decarboxylation of 94 to give the intermediates 95 (Scheme 7.14). The mesylates 97 are preferred to the analogous carbonates for the alkoxycarbonylation of optically active propargylic compounds in order to decrease the loss of optical purity in the products 98 [15]. In addition to the simple propargylic compounds of type 89, cyclic carbonates or epoxides such as 99 can also be used [138]. The obtained products 100 contain an additional hydroxy function. 

Cyclic epoxides such as 124 can react in two ways with strong bases (a) via abstraction of a /3-proton to form allylic alcoholates 125 or (b) by deprotonation at the epoxide carbon atom forming the intermediate 126 and, after electrophilic substitution, the epoxides 128. If there is a suitable C—H bond in the vicinity of the C-Li moiety, intramolecular carbenoid insertion reactions to 127 may take place (equation 27) ° . ... 

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. 

Alkenylsilanes and -stannanes, and arylsilanes and -stannanes are useful reagents for transfer of an sp -carbon unit to electrophiles under titanium catalysis. Epoxides are opened by TiCE to generate cationic carbon, which is successfully trapped with bis(trimethylsilyl)propene as an aUcenylsilane (Eq. 122) [305]. Other Lewis acids, for example ZnCla, SnCU, and BF3 OEt2, proved less satisfactory. Cyclic epoxides such as cyclopentene and cyclohexene oxides gave poorer yields. An intramolecular version of this reaction proceeded differently (Eq. 123) [305]. Eqs (124) and (125) illustrate diastereoselective alkenylation and arylation of (A,0)-acetals that take advantage of the intramolecular delivery of alkenyl and aryl groups [306], Cyclic ethers... 

Scheme 5.16. Bismuth bromide-catalyzed formation of cyclic carbonates from epoxides and DMF [97CC95].

SCHEME 4.6 Partial carbonation of epoxidized vegetable oil. (Reprinted from O. Figovsky, L. Shapovalov, A. Leykin, O. Birukova, and R. Potesshnikova, Nonisocyanate Polyurethanes Based on Cyclic Carbonates and Nanostructures Composites, J. Scientific Israel Technology Advanced 14, no. 4 (2012) 95-106. With permission.)... 

North, M. Synthesis of Cyclic Carbonates from Epoxides and Carbon Dioxide Using Bimetallic Aluminium (Salen) Complexes, ARKTVOC, no. i (2012) 610-628. 

Regioselectivity may also be controlled by n-interaction, as seen in the aluminum hydride reduction of unsaturated cyclic epoxides (e.g., 52). The observed regiochemical outcome was explained by an intermediate n-complex (53) in which the substrate is essentially planar. This model, which is supported by semiempirical calculations, minimizes axial-attack effects and emphasizes subtle electronic factors as well as hydride donor-carbon distances [94TL6647]. 

Polymer supported crown ether/metal salt Prep, of cyclic carbonates from epoxides and CO2 ... 

A siUca-SIL [BMIM]BF4 material was synthesized [80]. The catalyst proved to be an efHdent heterogeneous catalyst for solventless synthesis of cyclic carbonates from epoxides and CO2 under supercritical conditions, which required no additional organic solvents either for the reaction or for the separation of product. High yields with excellent selectivity were obtained. Moreover, the catalyst could be easily... 

Figure 8.18 Possible mechanism for (a) cycli2ation reactions of epoxides and (b) one-pot synthesis of cyclic carbonate from epoxide and CO over polymer-supported nano-gold...

Darensbourg DJ, Lewis SJ, Rodgers JL, Yarbrough JC (2003) Carbon dioxide/epoxide coupling reactions utilizing Lewis base adducts of zinc halides as catalysts. Cyclic carbonate versus polycarbonate production. Inorg Chem 42 581-589... 

Abstract This chapter deals with the utilization of CO2 in the carboxylation of alcohols, diols, polyols, and epoxides to create a variety of compounds such as linear carbonates, cyclic monomeric carbonates, and polycarbonates. Homogeneous, heterogenized, and heterogeneous catalysts are described. The problem of water elimination is considered and routes for water-trapping discussed. DPT calculations used to support the reaction mechanism are presented with the identified transition states relevant to various mechanistic scenarios. 

Dibenedetto A, Aresta M, Nocito F, Pastore C, Venezia AM, Chirykalova E, Kononenko VI, Shevchenko VG, Chupova lA (2006) Synthesis of cyclic carbonates from epoxides use of reticular oxygen of AI2O3 or AI2O3-supported CeOx for the selective epoxidation of propene. Catal Today 115 117-123... 

Song J, Zhang Z, Han B, Hu S, Li W, Xie Y (2008) Synthesis of cyclic carbonates from epoxides and CO2 catalyzed by potassium halide in the presence of -cyclodextrin. Green Chem 10 1337-1341... 

Shibata I, Mitani I, Imakuni A, Baba A (2011) Highly efficient synthesis of cyclic carbonates from epoxides catalyzed by indium tribromide system. Tetrahedron Lett 52 721-723... 

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". 

As described in this subsection, metal halides, metal complexes and water can improve the activities of ILs for the synthesis of cyclic carbonates from epoxides and CO2. A generally accepted reaction mechanism for those bi-functional catalyst systems can be drawn as Scheme 5. Because these additives have Lewis acidic nature, they would interact with the oxygen atom of the epoxide. On the other hand, the basic anion of IL would attack the less hindered carbon atom of the epoxide ring. Such cooperative activation of the epoxide should make the ring opening easier, being the reason of the promotional effects of the additives. In some cases, the additives may have a role in the activation of CO2. 

If other organocatalysts were capable of catalyzing mostly the polymerization of carbonyl-containing monomers (see previous sections), NHCs were found advantageous to polymerize a variety of monomers, including not only heterocycles such as lactones, lactide, cyclic carbonates, cyclic siloxanes, epoxides, NCAs but also bis-aldehydes and both acrylates and methacrylates. 

W.J. Kruper, D.V. Dellar, Catalytic formation of cyclic carbonates from epoxides and COj with chromium metalloporph)frinates, J. Org. Chem. 60 (1995) 725-727. 

A. Monassier, V. D Elia, M. Cokoja, H. Dong, J.DA. Pelletier, J.-M. Basset, F.E. Kuhn, S)mthesis of cyclic carbonates from epoxides and CO under mild conditions using a simple, highly efiScient niobium-based catalyst, ChemCatChem 5 (2013) 1321-1324. 

Monassier, A. D Elia, V Cokoja, M. Dong, H. Pelletier, J. D.A. Basset, J.-M. Kuhn, F.E. Synthesis of Cyclic Carbonates from Epoxides and COj under Mild Conditions Using a Simple, Highly Efficient Niobium-Based Catalyst. Chem Cat Chem 2013,5, 1321-1324. 

Bai, D. Nian, G. Wang, G. Wang, Z. Titanocene Dichloride/KI An Efficient Catalytic System for Synthesis of Cyclic Carbonates from Epoxides and CO. Appl Or-ganometal. Chem. 2013, 27, 184-187. 

Lescouet, T Chizallet, C. Famisseng, D. The Origin of the Activity ofAmine-Func-tionalized Metal-Organic Frameworks in the Catalytic Synthesis of Cyclic Carbonates from Epoxide and CO. Chem Cat Chem 2012,4,1725-1728. 

Zalomaeva, O. V. Maksimchuk, N. V Chibiryaev, A. M. Kovalenko, K.A. Fedin, V. P Balzhinimaev, B.S. Synthesis of Cyclic Carbonates from Epoxides or Olefins and CO Catalyzed by Metal-organic Frameworks and Quaternary Ammonium salts. J. Energ. Chem. 2013, 22, 130-135. 

Pescarmona, P.P. Taherimehr, M. Challenges in the Catalytic Synthesis of Cyclic and Polymeric Carbonates from Epoxides and CO. Catal. Sci. TechnoL, 2012, 2, 2169-2187. 

Regioselectivity of C—C double bond formation can also be achieved in the reductiv or oxidative elimination of two functional groups from adjacent carbon atoms. Well estab llshed methods in synthesis include the reductive cleavage of cyclic thionocarbonates derivec from glycols (E.J. Corey, 1968 C W. Hartmann, 1972), the reduction of epoxides with Zn/Nal or of dihalides with metals, organometallic compounds, or Nal/acetone (seep.lS6f), and the oxidative decarboxylation of 1,2-dicarboxylic acids (C.A. Grob, 1958 S. Masamune, 1966 R.A. Sheldon, 1972) or their r-butyl peresters (E.N. Cain, 1969). 

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