Hydrocarboxylation of olefins

Having greater resemblance to natural fatty acids are the products of the coordination-catalyzed hydrocarboxylation of olefins with water and carbon monoxide (Reppe reaction) [58] ... 

Historically, the rhodium catalyzed carbonylation of methanol to acetic acid required large quantities of methyl iodide co-catalyst (1) and the related hydrocarboxylation of olefins required the presence of an alkyl iodide or hydrogen iodide (2). Unfortunately, the alkyl halides pose several significant difficulties since they are highly toxic, lead to iodine contamination of the final product, are highly corrosive, and are expensive to purchase and handle. Attempts to eliminate alkyl halides or their precursors have proven futile to date (1). 

Metal-catalysed hydrocarboxylation of olefins (Equation 3) is the poor relative of the more famous hydroformylation. It generally requires forcing reaction conditions and suffers from mediocre activities and selectivities (n/i ratio). Moreover, the same products can be made via hydroformylation and oxidation of the aldehyde product.431 Consequently, there are few industrial applications of hydrocarboxylation e.g. Ni(CO)4-catalysed production of propionic acid by hydrocarboxylation of ethylene.432,433... 

Figure 8 Proposed catalytic cycle in the Pdf tppts)j-catalysed hydrocarboxylation of olefins.

The acid-catalyzed hydrocarboxylation of olefins (the Koch reaction) can be performed in a number of ways.565 In one method, the olefin is treated with carbon monoxide and water at 100 to 350°C and 500 to 1000 atm pressure with a mineral-acid catalyst. However, the reaction can also be performed under milder conditions. If the olefin is first treated with CO and catalyst and then water added, the reaction can be accomplished at 0 to 50°C and 1 to 100 atm. If formic acid is used as the source of both the CO and the water, the reaction can be carried out at room temperature and atmospheric pressure.566 The formic acid procedure is called the Koch-Haaf reaction (the Koch-Haaf reaction can also be applied to alcohols, see 0-103). Nearly all olefins can be hydrocarboxylated by one or more of these procedures. However, conjugated dienes are polymerized instead. 

TABLE 7.4. Hydrocarboxylation of Olefins Catalyzed by Chiral Pd(II) Complexes... 

The salt production can be circumvented by performing the selective Pd/ tppts-catalysed carbonylation of benzyl alcohol in an acidic aqueous biphasic system (Fig. 1.36) [106]. This methodology was also applied to the synthesis of ibuprofen (see earlier) by biphasic carbonylation of l-(4-isobutylphenyl)ethanol [107] and to the biphasic hydrocarboxylation of olefins [108]. 

Carboxylic acids and their derivatives, esters, amides, anhydrides, and acyl halides, are formally synthesized from olefins, carbon monoxide, and compounds represented with HX where X- equals OR-, NR2-, etc (see Scheme 1). Considering that the chiral aldehydes obtained by asymmetric hydroformylation of viny-larenes are often oxidized in order to exhibit biological activities, asymmetric hydrocarboxylation and its related reactions naturally attract much attention. Unfortunately, however, as yet only less successful work has been reported on this subject than on hydroformylation. Palladium(II) is most commonly used for this purpose. Asymmetric hydrocarboxylation of olefins was first reported in 1973 by Pino using PdCl2 and (-)-DIOP [105]. Chiusoh reached 52% ee in the... 

Hydrazine, 155, 211, 327, 368, 454 Hydrazine hydrate, 26 Hydrazoic acid, 211-213, 403 Hydrazones, 221 Hydriodic acid, 213-214,221 Hydroboration, 60, 176 Hydrobromic acid, 214-215 Hydrocarbostyril, 335 Hydrocarboxylation of olefins, 290 Hydrocinnamohydroxamic acid, 335 Hydrocyanation, 127, 128 Hydrofluoric acid, 201 Hydroformylation, 80 Hydrogen, 204 Hydrogen bromide, 204 Hydrogen chloride, 204, 215 Hydrogen cyanide, 261 Hydrogen fluoride, 215-216 Hydrogen fluoride-Antimony pentafluo-ride, 216... 

Nevertheless, it must be pointed out that the formation of such transient species has never been spectroscopically observed. Native CDs are effective inverse phase-transfer catalysts for the deoxygenation of allylic alcohols, epoxydation,or oxidation " of olefins, reduction of a,/ -unsaturated acids,a-keto ester,conjugated dienes,or aryl alkyl ketones.Interestingly, chemically modified CDs like the partially 0-methylated CDs show a better catalytic activity than native CDs in numerous reactions such as the Wacker oxidation,hydrogenation of aldehydes,Suzuki cross-coupling reaction, hydroformylation, " or hydrocarboxylation of olefins. Methylated /3-CDs were also used successfully to perform substrate-selective reactions in a two-phase system. 

The copolymerization of carbon monoxide and olefins forms the polyketone in Equation 17.65, and this polymerization is closely related to the hydroesterification and hydrocarboxylation of olefins. The rate of reaction of the acyl intermediate that was generated in the hydroesterification process with olefin or alcohol differentiates the formation of copolymer from the formation of monomeric esters. This difference in relative rates for reaction of the acyl intermediate with olefin versus alcohol results from a change in the ancillary ligand on the palladium, as described in this section. 

The catalytic hydrocarbonylation and hydrocarboxylation of olefins, alkynes, and other TT-bonded compounds are reactions of important industrial potential.Various transition metal complexes, such as palladium, rhodium, ruthenium, or nickel complexes, have widely been used in combination with phosphines and other types of ligands as catalysts in most carbonylation reactions. The reactions of alkenes, alkynes, and other related substrates with carbon monoxide in the presence of group VIII metals and a source of proton affords various carboxylic acids or carboxylic acid derivatives.f f f f f While many metals have successfully been employed as catalysts in these reactions, they often lead to mixtures of products under drastic experimental conditions.f i f f f In the last twenty years, palladium complexes are the most frequently and successfully used catalysts for regio-, stereo-, and enantioselective hydrocarbonylation and hydrocarboxylation reactions.f ... 

In the last five years interesting publications have appeared on the hydrocarboxylation of olefins in aqueous-organic two-phase systemsJ ° The catalytic systems consist of water-soluble phosphine ligands and a palladium complex in an acidic medium, resulting in high yields and selectivities for the hydrocarboxylation of styrene derivatives and terminal olefins (Eq. 

Many experiments have been carried out with the objective of reducing the drastic reaction conditions which are necessary for carbonylation of olefins. Tetteroo [474] succeeded in stoichiometric hydrocarboxylation of olefins at 55-60 °C and atmospheric pressure with UV irradiation. In the presence of cobalt catalysts the reaction is accelerated remarkably by addition of 5-10 % of hydrogen to carbon monoxide (about factor 3). Obviously the acceleration is caused by favoring the formation of hydrocarbonyl from Co2(CO)g and hydrogen. 

Some products available by hydrocarboxylation of olefins are listed in table 46. 

Carbonylation of Various Structures Table 46. Hydrocarboxylation of olefins... 

Pino P, Piacenti F, Bianchi M (1977) Hydrocarboxylation of olefins and related reactions. Org Synth Met Carbonyls 2 233-296... 

Hydrocarboxylation of olefins with CO2 and H2 is attractive because it is a thermodynamically feasible and atom-economic transformation of CO2. However... 

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