Oxidative carboxylation of olefins

The oxidative carboxylation of olefins appears to be a very interesting synthetic methodology for synthesizing CCs, starting from cheap and easily available reagents such as C02 and 02 (Equation 7.16). 

The direct oxidative carboxylation of olefins has great potential, and many advantages. Notably, it does not require the C02 to be free of dioxygen this is an especially attractive feature, as the cost to purify C02 is extremely high, and may discourage its use. Moreover, the direct oxidative carboxylation of olefins can couple two processes-the epoxidation of olefins, and the carbonation of epoxides. Hence, the process makes direct use of those olefins that are available commercially at low price, and which represent an abundant feedstock. Such an approach also avoids having to isolate the epoxide. 

Oxidative Carboxylation of Olefins to Afford Cyclic Carbonates... 

The direct oxidative carboxylation of olefins [108-110] couples two processes, namely (1) the epoxidation of the olefins and (2) the carbonation of the epoxide, occurring in the same reactor. Interestingly, it has been shown that CO2 modulates the oxidant properties of O2 [111]. 

Aresta M, Dibenedetto A (2002) Carbon dioxide as building block for the synthesis of organic carbonates behavior of homogeneous and heterogeneous catalysts in the oxidative carboxylation of olefins. J Mol Catal 182-183 399-409... 

Aresta M, Dibenedetto A, Tommasi I (2000) Direct synthesis of organic carbonates by oxidative carboxylation of olefins catalyzed by metal oxides developing green chemistry based on carbon dioxide. Appl Organomet Chem 14 799-802... 

Therefore, the direct synthesis of cyclic carbonates from olefins instead of epoxides, a so-called one-pot "oxidative carboxylation" of olefins, would be appealing. The oxidative carboxylation synthesis from olefins can be roughly viewed as the coupling of two sequential processes of epoxidation of olefins and CO2 cycloaddition to epoxides formed (Scheme 18). The reaction uses easily available and low-priced chemicals of olefins as substrates and, moreover, preliminary synthesis and separation of epoxides would be avoided. So, the oxidative carboxylation would be a simpler and cheaper carbonate synthesis process with industrial potential from environmental and economic points of view. Although the three-component couplings have been known at least since 1%2 [66], up to date, only a few works have been made on these reactions in contrast to extensive studies on the addition reactions of CO2 to epoxides in ILs as catalyst/or solvent. 

The oxidative carboxylation of olefins to cyclic carbonates can proceed through the first step of epoxidation of olefins and the subsequent cycloaddtion of CO2 to epoxides formed (Scheme 18). Thus it is supposed that a system of combining catalysts effective for the first step and for the second one would be effective for the direct synthesis of cyclic carbonates via the oxidative carboxylation of olefins. Indeed the direct preparation of carbonates was successfully achieved with a few catalyst systems including ILs coupled with oxidation catalysts. One patent [66] reported that the cyclic carbonate was formed from an olefin, CO2, and oxygen in the presence of dual catalysts. The catalyst system includes a heavy metal compound and a quaternary ammonium hydroxide or haUde. However, the heavy metal compounds would easily induce the corrosion of equipments and result in the undesired reduction of activity and selectivity. 

Scheme 23. Proposed mechanism of aerobic oxidative carboxylation of olefins catalyzed by Ru(TPP)(0)2/IL. X = I-, Br-...

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. 

Scheme 1.13 Oxidative carboxylation of olefins with homogeneous and heterogeneous catalysts.

Seheme 1.14 Catalytic cycle for the formation of carbonate via oxidative carboxylation of olefins. 

The palladium(II)-mediated oxidative coupling of olefins with oxygen-nucleophiles (ROH water, alcohols, carboxylic acids) is a stoichiometric reaction with respect to Pd(II), resulting in an oxygenated product and Pd(0). To convert Pd(0) back to Pd(II) and start a new reaction cycle, a reoxidation reaction (which can itself be stoichiometric or catalytic) using a terminal oxidant is required. In this way, the overall process becomes catalytic with respect to the expensive Pd salt. 

Oxidative cleavage of carbon-carbon double bonds or v/c-diols can lead to aldehydes, ketones or carboxylic acids depending upon the conditions employed. Oxidative cleavage of olefins is important from the viewpoint of... 

Another product of the reaction of an olefin with the O2/ CO2 mixture in the presence of Rh is the cyclic carbonate (VII) [3]. Only few reports can be found in the literature on the direct synthesis of carbonates from olefins, dioxygen and carbon dioxide, despite the usefulness of this reaction that avoids, with respect to the reaction of epoxides with carbon dioxide, the preliminary synthesis of epoxides. We have found that the product distribution in the oxidative carboxylation of styrene depends on the O2/ CO2 ratio and on the temperature (Scheme 3). As the epoxide is one of the oxidation products of styrene, it could be the origin of styrene carbonate. We have evidence that the formation of the... 

Oxidative cleavage of olefins to ketones and carboxylic acids by the usual... 

From a preparative point of view the commonest use of oxidative cleavage of olefins by the usual oxidizing agents is for preparation of ketones and, even more so, of carboxylic acids. Azelaic acid is obtained by permanganate oxidation of ricinoleic acid as follows 113... 

Better yields are often obtained when ozone is used for oxidative cleavage of olefins to carboxylic acids or of cycloalkenes to dicarboxylic acids. Olefinic double bonds are very much more easily attacked by ozone than are aromatic systems, so that arylethylene derivatives can be successfully treated with ozone without appreciable effect on the ring. If the ozonide which is formed initially is decomposed with water, the aldehyde is obtained together with hydrogen peroxide and other products ... 

Examples of the oxidative reactions of olefins with carboxylic acids are shown in Equations 16.107-16.109. These examples illustrate the selectivities of the oxidations of ethylene, acylic alkenes, and cyclic alkenes. The reactions of alkenes with carboxylic adds generate either vinylic esters or allylic esters. 

The oxidative aminations of olefins have been reported in parallel witfi the oxidations of olefins witii alcohols, phenols, and carboxylic acids. These reactions are generally conducted with amides or imides amines are tfiought to be protonated by the acidic medium or to bind the metal center too tightly to allow for the catalytic chemistry to occur. Some exceptions noted below have been observed with arylamines or with rhodium catalysts. These oxidations have been conducted botfi intermolecularly and intramolecularly The oxidations have been conducted with benzoquinone, with copper, or with alone as the... 

Antonelli, E., D Aloisio, R., Gambaro, M., et al. (1998). Efficient Oxidative Cleavage of Olefins to Carboxylic Acids with Hydrogen Peroxide Catalyzed by Methyltrioctylammonium Tetrakis(oxodiperoxotungsto)phosphate(3-) under Two-phase Conditions. Synthetic Aspects and Investigation of the Reaction Course, J. Org. Chem., 63, pp. 7190-7206. 

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