Carbonyls, selective olefination

Deformation of symmetrical orbital extension of carbonyl or olefin compounds was proposed to be the origin of the facial selectivities. We illustrate the unsymmetrical orbital phase environment of % orbitals of carbonyl and olefin groups and facial selectivities in Fig. 1 [3, 4]. There are in-phase and out-of-phase combinations of... 

Reduction of carbon-carbon double bond Microalgae easily reduce carbon-carbon double bonds in enone. Usually, the reduction of carbonyl group and carbon-carbon double bond proceeds concomitantly to afford the mixture of corresponding saturated ketone, saturated alcohol, and unsaturated alcohol because a whole cell of microalgae has two types of reductases to reduce carbonyl and olefinic groups. The use of isolated reductase, which reduces carbon-carbon double bond chemoselectively, can produce saturated ketones selectively. 

Rhodium catalyzed carbonylations of olefins and methanol can be operated in the absence of an alkyl iodide or hydrogen iodide if the carbonylation is operated in the presence of iodide-based ionic liquids. In this chapter, we will describe the historical development of these non-alkyl halide containing processes beginning with the carbonylation of ethylene to propionic acid in which the omission of alkyl hahde led to an improvement in the selectivity. We will further describe extension of the nonalkyl halide based carbonylation to the carbonylation of MeOH (producing acetic acid) in both a batch and continuous mode of operation. In the continuous mode, the best ionic liquids for carbonylation of MeOH were based on pyridinium and polyalkylated pyridinium iodide derivatives. Removing the highly toxic alkyl halide represents safer, potentially lower cost, process with less complex product purification. 

The present economic and environmental incentives for the development of a viable one-step process for MIBK production provide an excellent opportunity for the application of catalytic distillation (CD) technology. Here, the use of CD technology for the synthesis of MIBK from acetone is described and recent progress on this process development is reported. Specifically, the results of a study on the liquid phase kinetics of the liquid phase hydrogenation of mesityl oxide (MO) in acetone are presented. Our preliminary spectroscopic results suggest that MO exists as a diadsorbed species with both the carbonyl and olefin groups coordinated to the catalyst. An empirical kinetic model was developed which will be incorporated into our three-phase non-equilibrium rate-based model for the simulation of yield and selectivity for the one step synthesis of MIBK via CD. 

In contrast to kinetic models reported previously in the literature (18,19) where MO was assumed to adsorb at a single site, our preliminary data based on DRIFT results suggest that MO exists as a diadsorbed species with both the carbonyl and olefin groups being coordinated to the catalyst. This diadsorption mode for a-p unsaturated ketones and aldehydes on palladium have been previously suggested based on quantum chemical predictions (20). A two parameter empirical model (equation 4) where - rA refers to the rate of hydrogenation of MO, CA and PH refer to the concentration of MO and the hydrogen partial pressure respectively was developed. This rate expression will be incorporated in our rate-based three-phase non-equilibrium model to predict the yield and selectivity for the production of MIBK from acetone via CD. 

Transition metals can display selectivities for either carbonyls or olefins (Table 20.3). RuCl2(PPh3)3 (24) catalyzes reduction of the C-C double bond function in the presence of a ketone function (Table 20.3, entries 1-3). With this catalyst, reaction rates of the reduction of alkenes are usually higher than for ketones. This is also the case with various iridium catalysts (entries 6-14) and a ruthenium catalyst (entry 15). One of the few transition-metal catalysts that shows good selectivity towards the ketone or aldehyde function is the nickel catalyst (entries 4 and 5). Many other catalysts have never been tested for their selectivity for one particular functional group. 

Though important results have already been obtained in the carbonylation of olefins, the field still remains open. Development of more active, efficient and stable catalysts based also on less expensive metals will make the carbonylation processes more attractive. Carbonylation of less common olefins, including functionalised ones, has to be explored in more depth. Other important targets are the efficient living copolymerisation, the multiple olefin insertion producing non-alternating copolymers and the selective synthesis of unsaturated products like acrylates and methacrylates. 

When the enthalpies of reaction between branched ketones and the corresponding 1,1-disubstituted alkenes are calculated using the multiple enthalpies of formation available for the latter, the following ranges are obtained Me/i-Pr, 196.6 to 200.5 Et/i-Pr, 201.2 to 206.6 and Me/t-Bu, 200.5 to 205.1 kJmol-1. Perhaps it is reasonable to conclude that the reaction enthalpies for the branched compounds either will be approximately constant, as for the unbranched ketone/alkene conversions, or will be more endothermic with branching, as in the branched aldehyde/alkene conversions. In either case, the least endothermic reaction enthalpy for the Me/i-Pr conversion above seems inconsistent and therefore the enthalpies of formation for 2,3-dimethyl-l-butene from References 16 or 26, which are essentially identical, should be selected. These enthalpies were also selected in a previous section. However, there is too much inconstancy, as well as too much uncertainty, in the replacement reactions of carbonyls and olefins to be more definitive in our conclusions. 

Various polymer-supported hydrides have been applied successfully to reductions of both carbonyl and olefin groups. Rajasree and Devaky13 describe a cross-linked polystyrene-supported ethylenediamine borane reagent for the selective reduction of aldehydes in the presence of ketones (entry 9). This borane reagent is easily prepared and can be recycled after completion of the reaction. This is a practical alternative to standard borane reagents such as diborane, borane-amine, or borane-sulfide complexes. 

The four-coordinate sqnare planar iron(n) porphyrins discussed above are not only of great valne in heme protein model chemistry, but also in chemical applications, since they undergo a wealth of ligand addition reactions. For example it has been shown that TPPFe complexes are active catalysts for important carbon transfer reactions in organic chemistry and are found to catalyze the stereoselective cyclopropanation of aUcenes, olefin formation from diazoalkanes, and the efficient and selective olefination of aldehydes and other carbonyl compounds. The active species in these carbon transfer reactions are presumably iron porphyrin carbene complexes. " It was also found that ferrous hemin anchored to Ti02 thin films reduce organic halides, which can pose serious health problems and are of considerable environmental concern because of their prevalence in groundwater. ... 

In the cobalt-catalyzed photochemical carbonylation of olefins, hydroformyla-tion can be performed easily at ambient temperature (and high pressure) with high primary aldehyde selectivities (cf. Section 2.1.1) [59]. Under comparable conditions allylic amines are carbonylated to 2-pyrrolidinone, Al,/V -diallylurea, and A -allyl-3-butenamide [60]. Photochemical methoxycarbonylation of olefins is possible at ambient conditions, i.e., at room temperature and atmospheric pressure [61]. 

Mechanistically, when R =H, the usual syn selectivity is observed due to the preference of the reactants to adopt an antiperiplanar transition state, which places the aldehyde carbonyl and olefin opposite each other. When the j -methyl substituent is added, the transition state prefers the synclinal conformation (495) therefore leading to the formation of 494. 

It is known that methylation with diazomethane selectively methylates FFAs in the presence of FA esters. Caution is required, as diazomethane is a dangerous substance. Under inappropriate conditions, derivatization with diazomethane leads to the formation of artifacts. Functional groups such as phenol, enol, and carbonyl, or olefinic bonds can be affected. The less-dangerous methylation agents such as trimethylsilyldiazomethane (TMS-CHN2) and lit-hiated TMS-CHN2 have been suggested to replace diazomethane. Benzyl esters can be produced by the use of phenyldiazomethane. 

Doubly carbonylated cyclic olefins are reactive candidates as acceptors for y-selective conjugate addition of alkylidene malononitriles. The highly... 

A review of facial selections in reactions of carbonyl and olefin systems has led to a new theory, orbital phase environment, a generalized idea of the secondary orbital interaction between non-reacting centres and the unsynunefrization of the orbitals at the reacting centres arising from the in-phase and out-of-phase overlapping with... 

Carbonylation of Olefins. A catalyst, containing 5% Pd on active carbon exhibits high activity and selectivity in propylene carbonylation (14) (Table 2). The catalyst is prepared by soaking active carbon by H2PdCl4 solution further, H2PdCl4 is converted into Pd(OH)2 by precipitation with sodium carbonate, with subsequent reduction of Pd(II) to Pd(0) by molecular hydrogen at room temperature. The carbonylation reaction is carried out under static conditions in... 

Carbonylation of Olefins. Two catalysts 1% Pd/0.8 CaNaY, and 1% Pd/HMOR were tested in propylene carbonylation (14). Both Pd-containing zeolite catalysts exhibit high activity and selectivity, conversion to butyric acids being 97-99% (Table 6). The change of the nature of the zeolite does not affect the yield and composition of the reaction products. However, Pd/zeolite catalysts are destroyed during the cause of the experiments by both the acid used as the solvent and the acid formed in the reaction. According to x-ray analysis 100% destruction of zeolite structure was observed after the end of experiment. 

It is often difficult to induce selective addition to double bonds in the presence of triple bonds because of the reactivity of the latter. Dicobalt octa-carbonyl selectively adds to a triple bond in the presence of a double bond and allows selective transformation of the non-co-ordinated olefinic bond. Removal of the protecting metal is simple. Thus vinylacetylenes when treated with strong acids usually form the products of hydration of the triple bond, and the ene-yne-ol (140) reacts with fluoroboric-acetic acid at 25 C for 24 h to form an intractable mixture. Its complex (141) reacted at 0 °C for 15 min to give 91 % of (142) on work-up, which implies a metal-stabilized carbonium ion intermediate. Oxidative degradation with Fe(N03)3 generates the acetylene (143) in excellent yield. 

Selective Olefination of Carbonyl Compounds via Metal-Catalyzed Carbene Transfer from Diazo Reagents... 

Abstract A number of transition metal complexes are capable of catalyzing selective olefination of carbonyl compounds, including aldehydes, activated and unactivated ketones, with diazo reagents in the presence of triphenylphosphine or related tertiary phosphines. These catalytic olefination reactions can be carried out in a one-pot fashion under neutral conditions with the use of different diazo reagents as carbene sources, typically affording olefins in high yields and high stereoselectivity. 

A variety of pentacoordinated spirophosphoranes undergo olefination with aldehydes in the presence of t-BuOK to give a,p-unsaturated esters, amides, and nitriles with high Z selectivity (Scheme 46) [212, 217], This method has recently been extended to the Z selective olefination of ketones by modifying the pentacoordinated spirophosphoranes, which are readily prepared through the reaction of the corresponding P-H phosphoranes with a-halo carbonyl compounds in the presence of DBU [218],... 

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