Hydrocarboxylation, of olefins with

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] ... 

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

In this chapter, we have reviewed theoretical studies of selected transition metal-catalyzed transformation of CO2 (i) hydrogenation of CO2 with H2 (ii) coupling reactions of CO2 and epoxides (iii) reduction of CO2 with organoborons (iv) carboxylation of olefins with CO2 and (v) hydrocarboxylation of olefins with CO ... 

In transition metal-catalyzed hydrocarboxylation of olefins with CO2 and H2, CO2 is activated by M-ethyl bonds, which can be considered as electron-rich... 

If cobalt carbonylpyridine catalyst systems are used, the formation of unbranched carboxylic acids is strongly favored not only by reaction of a-olefins but also by reaction of olefins with internal double bonds ( contrathermo-dynamic double-bond isomerization) [59]. The cobalt carbonylpyridine catalyst of the hydrocarboxylation reaction resembles the cobalt carbonyl-terf-phos-phine catalysts of the hydroformylation reaction. The reactivity of the cobalt-pyridine system in the hydrocarboxylation reaction is remarkable higher than the cobalt-phosphine system in the hydroformylation reaction, especially in the case of olefins with internal double bonds. This reaction had not found an industrial application until now. 

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. 

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... 

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 ... 

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. 

Monflier et al. (1997) have suggested Pd catalysed hydrocarboxylation of higher alpha olefins in which chemically modified P-cyclodextrin (especially dimethyl P-cyclodextrin) is u.sed in water in preference to a co-solvent like methanol, acetone, acetic acid, acetonitrile, etc. Here, quantitative recycling of the aqueous phase is possible due to easy phase separation without emulsions. A similar strategy has been adopted by Monflier et al. (1998) for biphasic hydrogenations for water-in.soluble aldehydes like undecenal using a water-soluble Ru/triphenylphosphine trisulphonate complex with a. suitably modified p-cyclodextrin. 

Until there is a sufficient excess of ethene over [PdH(TPPTS)3] their fast reaction ensures that aU palladium is found in form of tratts-[Pd C(CO)Et (TPPTS)2]. However, at low olefin concentrations (e.g. in biphasic systems with less water-soluble olefins) [PdH(TPPTS)3] can accumulate and through its equihbrium with [Pd(TPPTS)3] (eq. 5.5) can be reduced to metallic palladium. This is why the hydroxycarbonylation of olefins proceeds optimally in the presence of Brpnsted acid cocatalyts with a weekly coordinating anion. Under optimised conditions hydrocarboxylation of propene was catalyzed by PdC + TPPTS with a TOE = 2507 h and l = 57/43 (120 °C, 50 bar CO, [P]/[Pd] = 4, P-CH3C6H4SO3H) [38], In neutral or basic solutions, or in the presence of strongly coordinatmg anions the initial hydride complex cannot be formed, furthermore, the fourth coordination site in the alkyl- and acylpaUadium intermediates may be strongly occupied, therefore no catalysis takes place. 

Finally, it should be apparent that the nature of the reaction media has a profound effect on the reactivity of this system, and that, particularly for secondary alcohols, generation of olefins (and metal hydrides) occurs quite easily. Since this involves only the organic equilibria, this situation is not unique to rhodium chemistry. Unless great care has been taken to eliminate possible contributions of the hydrido/olefin pathway to the total reaction scheme, then, the hydrocarboxylation route should probably be considered to be a contributing reaction with other catalytic systems. 

The Ni-catalyzed electrocarboxylation of differently activated olefins has been reported to afford selective CO2 incorporation via hydrocarboxylation [11]. However, no CO2 incorporation occurred with non-activated alkenes such as 1- or 4-octene. Carboxylation of olefins 3 and 4 should give some indication on the influence of the Rp substituent on the double bond. 

For technical purposes standard carbonylation catalysts such as Co2(CO)g and Ni(CO)4 have been used to prepare fatty-acid esters [1]. More recently, other catalysts based on Pd, Pt, Rh, and Ru found widespread use because of their better performance under milder reaction conditions [2]. As seen in eq. (1) and Table 1, hydrocarboxylation of simple olefins with palladium catalysts occurs at temperatures of 70-120 °C and 0.1-20 MPa, while cobalt catalysts needed 150-200 °C and 15-20 MPa. 

Hydrocarboxylation of the Ce-Cs a-olefins with cobaltcarbonyl/pyridine catalysts at 200 °C and 20 MPa gives predominantly the linear carboxylic acids. The acids and their esters are used as additives for lubricants. The Ce-Cio a-olefins are hydroformylated to odd-numbered linear primary alcohols, which are converted to polyvinylchloride (PVC) plasticizers with phthalic anhydride. Oligomerization of (preferably) 1 -decene, applying BF3 catalysts, gives oligomers used as synthetic lubricants known as poly-a-olefins (PAO) or synthetic hydrocarbons (SHC) [11, 12]. The C10-C12 a-olefins can be epoxidized by peracids this opens up a route to bifunctional derivatives or ethoxylates as nonionic surfactants [13]. 

Pd -catalyzed hydrocarboxylation of aromatic olefins leads directly to the requisite carboxylic acids (cf. Section 2.1.2.2) under mild conditions (Scheme 5). The reaction, with the aid of (5)-BNPPA (21), a chiral hydrogen phosphate, gives regio- and enantioselectively (S)-ibuprofen and (S)-naproxen, but the turnover efficiency as well as the enantioselectivity can still be improved [26]. 

The HSAB concept can also be applied to the related hydrocarboxylation reaction, in which carboxylic acids are produced from olefins, CO, water, and small amounts of hydrogen. With hard cobalt/tert-amine catalysts, the products are the hard carboxylic acids, whereas rhodium catalysts give mainly aldehydes. Rhodiiun makes the intermediate acyl complexes softer, and in the subsequent elimination step H2, which is softer than H2O, gives aldehyde as product. 

Ni(CO)4 are used, but this process has not found a commercial application either. The catalytic processes are run below 100 bar and above 250 °C. The catalyst precursors are nickel salts such as NiBr2- Nickel catalysts are very suitable for the carbonylation of atkynes, whereas for olefins, Co, Rh, Pd, Pt, and Ru are equally good, if not better. Characteristic of nickel catalysts in the hydrocarboxylation of a-olefins is that as a main product (60-70 %) the branched carboxylic acid is formed. With internal olefins, branched products are formed exclusively. It has also been shown that carbonylations in the presence of triphenylphosphine can be run under milder conditions than when Ni(CO)4 is used alone. 

Like many carbonylation processes, the hydrocarboxylation and hydroesterification reactions were first reported by Reppe. These first reactions involved the hydrocarboxylation of alkynes. These reactions were conducted with nickel carbonyl as catalyst and occurred with very low turnover numbers. Hydrocarboxylation and hydroesterification have now been studied extensively in both academic and industrial laboratories. As a result of these investigations, commercialization of this chemistry as part of new industrial processes has occurred, and the mechanism of these processes is now generally accepted. This section of Chapter 17 presents the scope and industrial applications of hydrocarboxylation and hydroesterification, the types of catalysts that have been used for these processes, and the elementary steps that constitute the catalytic cycle for olefin and alkyne hydroesterification. 

Cobalt, nickel, iron, ruthenium, and rhodium carbonyls as well as palladium complexes are catalysts for hydrocarboxylation reactions and therefore reactions of olefins and acetylenes with CO and water, and also other carbonylation reactions. Analogously to hydroformylation reactions, better catalytic properties are shown by metal hydrido carbonyls having strong acidic properties. As in hydroformylation reactions, phosphine-carbonyl complexes of these metals are particularly active. Solvents for such reactions are alcohols, ketones, esters, pyridine, and acidic aqueous solutions. Stoichiometric carbonylation reaction by means of [Ni(CO)4] proceeds at atmospheric pressure at 308-353 K. In the presence of catalytic amounts of nickel carbonyl, this reaction is carried out at 390-490 K and 3 MPa. In the case of carbonylation which utilizes catalytic amounts of cobalt carbonyl, higher temperatures (up to 530 K) and higher pressures (3-90 MPa) are applied. Alkoxylcarbonylation reactions generally proceed under more drastic conditions than corresponding hydrocarboxylation reactions. 

Interestingly, the hydrocarboxylation of fluorinated olefins [3,3,3-trifluoropropene (TFP) and pentafluorostyrene (PFS)] was realized to form useful fluorinated acids. The palladium complex PdCl2(dppf) [dppf = l,l-bis(diphenylphosphino)ferrocene] in the presence of SnCl2 at 125 °C and at 10 atm CO showed the highest catalytic activity with TFP (yield = 93%, selectivity = 99% in linear acid), and the catalyst PdCl2(dppb) afforded PFS hydrocarboxylation products in excellent yield and selectivity (Eq. 

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