Synthesis of Organic Cyclic Carbonates

Methanol is currently produced from syngas, which has been enriched with C02 and is derived from either a fossil fuel or biomass. A better approach might consist of the direct hydrogenation of pure C02, whilst transesterification with ethylene carbonate implies that ethylene, derived from oil refineries, should be used as the raw material. 

The urea route does not involve any specific carbon source for hydrogen and C02, as does that of methanol synthesis. Ideally, hydrogen should be produced chiefly from water splitting, and C02 from flue gas. 

The first reports describing the formation of cyclic carbonates (CCs) appeared during the early 1930s [99, 100], whilst the first patents (essentially related to the synthesis of ethene and propene carbonates) appeared more than 50 years ago [101, 102]. The Huntsman Corporation is one the world s largest producers of alkylene carbonates, with a capacity of 33 kt per year, covering approximately 50% of CC production worldwide. Today, CCs are widely used in the manufacture of 

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The synthesis of enantiomerically pure compounds is the challenging problem for organic chemists. The synthesis becomes obsolete if the intermediates produce racemic mixtures. The problem is particularly acute when the asymmetric centers do not reside in a rigid cyclic or polycyclic framework. To be able to carry out efficient syntheses of complex molecules, chemists have to control the sense of chirality at each chiral center as it is introduced in the course of synthesis. Monoalkyl- or dialkyl-boranes exhibit a remarkable chemo-, stereo-, and regioselectivity for the hydroboration of unsaturated compounds. This property, coupled with the capability for asymmetric creation of chiral centers with chiral hydroboration agents, makes the reaction most valuable for asymmetric organic synthesis. In some of the cases, however, this has been achieved by diborane itself as shown in the synthesis of monensin by Kishi et al. A stereospecific synthesis of its seven carbon. component has been accomplished by two hydroboration reactions (Eq. 129) 209. ... 

The reaction of CO2 with M-OR (R = alkyl, aryl) bonds is of industrial interest as it is related to the synthesis of molecular organic carbonates and polycarbonates based on the direct carboxylation of substrates such as alcohol, polyols, and epoxides. In this paragraph the kinetics and thermodynamics of the elementary step (4.18) are discussed, and the synthesis of organic carbonates (acyclic and cyclic) is discussed in Chap. 6. 

Aresta, M. Dibenedetto, A. Tommasi, I. Direct Synthesis of Organic Carbonates by Oxidative Carboxylation of Olefins Catalyzed by Metal oxides Developing Green Chemistry Based on Carbon Dioxide. Appl Organomet. Chem. 2000,14,799-802. Eghbali, N. Li, C.-J. Conversion of Carbon Dioxide and Olefins into Cyclic Carbonates in Water. Green Chem. 2007, 9, 213-215. 

The O-C bond formation is relevant to the synthesis of organic carbonates characterized by the 0-C(0)0 moiety. Both linear and cyclic carbonates are of industrial interest (Table 1.5). The semicarbonate species R0-C(0)0H is labile, as is the analogous RR N-C(0)0H. CH30-C(0)0H has only recently been generated in solution and characterized by IR [88a] and NMR spectroscopy [88b]. 

The above studies [8-10] strongly indicate the participation of silanol groups as acid sites in the amine-catalyzed reactions. The synergistic catalysis of immobilized organic bases and silanol groups has been highlighted by the cyclic carbonate synthesis from carbon dioxide and epoxide. Acid-base dual activation mechanism of the cyclic carbonate synthesis is widely accepted. Sakakura and coworkers [11] reported silica-supported phosphonium salts as highly active catalysts for the cyclic carbonate synthesis. The results for propylene carbonate synthesis are summarized... 

Molecular orbital calculations indicate that cyclo C-18 carbyne should be relatively stable and experimental evidence for cyclocarbynes has been found [25], Fig. 3B. Diederich et al [25] synthesised a precursor of cyclo C-18 and showed by laser flash heating and time-of flight mass spectrometry that a series of retro Diels-Alder reactions occurred leading to cyclo C-18 as the predominant fragmentation pattern. Diederich has also presented a fascinating review of possible cyclic all-carbon molecules and other carbon-rich nanometre-sized carbon networks that may be susceptible to synthesis using organic chemical techniques [26]. 

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... 

Tanaka and co-workers have reported two routes for the catalytic synthesis of cyclic silyl enol ethers from silacylobutanes. The strained silacarbo-cycle174 can react directly with an acid chloride175,176 or in a three-component reaction with an organic halide and carbon monoxide177 to yield cyclic products that contain an Si-O bond [Eqs. (68) and (69)]. 

Nobel prize in chemistry with Kurt Alder in 1950. He was awarded the prize for diene synthesis work, which led to improved methods of analyzing and synthesizing organic compounds. His research resulted in the discovery of carbon suhoxide. methods of dehydrating cyclical hydrocarbons using selenium, and determination of the structure of steroids. A student of Fischer -, he graduated from the University of Berlin. 

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