Palladium catalysts hydroxycarbonylation

Practical hydroxycarbonylation of olefins is usually carried out with palladium catalysts and requires rather elevated temperatures. Pd/TPPTS [36-39], Pd/TPPMS [40] and Pd/sulfonated XANTHPHOS (51) were all applied for this purpose. In general, TOF-s of several hundred h can be observed under the conditions of Scheme 5.11, and with propene the concentration ratio of linear and branched acids is around l/b=1.3-1.4 [36,38]. At elevated temperatures and at low phosphine/palladium ratios precipitation of palladium black can be observed. It is known, that the highly reactive [Pd(TPPTS)3] forms easily under CO from a Pd(II) catalyst precursor and TPPTS [37], and that in the presence of acids it is in a fast equilibrium with [PdH(TPPTS)3] [39] ... 

Hydrodehalogenation of aliphatic or benzylic halides were catalyzed by water soluble ruthenium phosphine complexes in the presence of sodium formate as hydrogen donor [194], Hydroxycarbonylations could also be performed with high palladium catalyst activities in biphasic systems [195-197]. 

Hydroxycarbonylation is very similar in scope to the preceding hydro-formylation almost any alkene can be used as starting material. The best results are obtained with palladium catalysts in acidic medium (and not with rhodium as in the 0x0 reaction). Cobalt is only active in basic medium at high pressure it is then capable to hydroxycarbonylate an internal olefin into a terminal ester (Table XIII). 

The majority of hydroxycarbonylation reactions have used vinyl arenes as model substrates because the reactions of these alkenes can provide enantio-enriched profens in a single step. Abermarle are believed to use hydroxycarbonylation in their production of commercial naproxen, although they are believed to use a monodentate phosphine/ palladium catalyst to produce the compound as a racemic mixture that is subsequently resolved into the desired S enantiomer. This catalyst is also understood to enable the preceding Heck reaction (Scheme 14.26). ... 

Hydroxycarbonylation and alkoxycarbonylation of alkenes catalyzed by metal catalyst have been studied for the synthesis of acids, esters, and related derivatives. Palladium systems in particular have been popular and their use in hydroxycarbonylation and alkoxycarbonylation reactions has been reviewed.625,626 The catalysts were mainly designed for the carbonylation of alkenes in the presence of alcohols in order to prepare carboxylic esters, but they also work well for synthesizing carboxylic acids or anhydrides.137 627 They have also been used as catalysts in many other carbonyl-based processes that are of interest to industry. The hydroxycarbonylation of butadiene, the dicarboxylation of alkenes, the carbonylation of alkenes, the carbonylation of benzyl- and aryl-halide compounds, and oxidative carbonylations have been reviewed.6 8 The Pd-catalyzed hydroxycarbonylation of alkenes has attracted considerable interest in recent years as a way of obtaining carboxylic acids. In general, in acidic media, palladium salts in the presence of mono- or bidentate phosphines afford a mixture of linear and branched acids (see Scheme 9). 

As with carboxylic acids obtained by palladium hydroxycarbonylation, their derivatives esters, amides, anhydrides and acyl halides are synthesized from alkenes, CO and HX (X = OR, NR2 etc.). The Pd-catalyzed methoxycarbonylation is one of the most studied reactions among this type of catalyzed carbonylations and has been reviewed and included in reports of homogeneous catalysis.625, 26 The methoxycarbonylation has been applied to many different substrates to obtain intermediates in organic syntheses as well as specific products. For instance, the reaction has been applied for methoxycarbonylation of alkynes666 Highly efficient homogeneous Pd cationic catalysts have been reported and the methoxycarbonylation of alkynes has been used to develop economically attractive and environmentally benign process for the production of methyl... 

In order to keep the mild conditions, hydroxycarbonylation has been performed in biphasic media, maintaining the catalyst in the aqueous phase thanks to water-soluble mono- or diphosphine ligands. In the presence of the sodium salt of trisulfonated triphenylphosphine (TPPTS), palladium was shown to carbonylate efficiently acrylic ester [19], propene and light alkenes [20,21] in acidic media. For heavy alkenes the reduced activity due to the mass transfer problems between the aqueous and organic phases can be overcome by introducing an inverse phase transfer agent, and particularly dimeihyl-/-i-cyclodextrin [22,23]. Moreover, a dicationic palladium center coordinated by the bidentate diphosphine ligand 2,7-bis(sulfonato)xantphos (Fig. 2) catalyzes, in the presence of tolylsulfonic acid for stability reasons, the hydroxycarbonylation of ethylene, propene and styrene and provides a ca. 0.34 0.66 molar ratio for the two linear and branched acids [24],... 

In line with the above mechanism, catalyst deactivation by formation of palladium black can be retarded by increasing the [P]/[Pd] ratio, however, only on the expense of the reaction rate. Bidentate phosphines form stronger chelate complexes than TPPMS which may allow at working with lower phosphine to palladium ratios. Indeed, the palladium complex of sulfonated XANTPHOS (51) proved to be an effective and selective catalyst for hydroxycarbonylation of propene, although at [51]/[Pd] < 2 formation of palladium black was still observed. The catalyst was selective towards the formation of butyric acid, with 1/b = 65/35 [41]. 

A variant of this process, studied by DuPont and DSM [32c], includes the hydrocarboxylation (hydroxycarbonylation) of butadiene with carbon monoxide and water this technology offers potential savings in raw material costs. The reaction primarily yields 3-pentenoic acid using a palladium/crotyl chloride catalyst system, with a selectivity of 92%. Further conversion of pentenoic acids by reaction with carbon monoxide and methanol and a palladium/ferrocene/phosphorous ligand catalyst has demonstrated a selectivity to dimethyl adipate of 85% the latter is finally hydrolyzed to AA. The main problem in this reaction is the propensity of pentenoic acid to undergo acid-catalyzed cyclization to y-valerolactone one way to circumvent the problem is to carry out the hydrocarboxylation of pentenoic acid using the y-valerolactone as the solvent. 

Palladium complexes of TPPTS and TPPMS have been employed extensively as catalysts for carbonylation, hydroxycarbonylation, and C—C cross-coupling reactions (cf. Section 6.6). Hydroxycarbonylation of bromobenzene in biphasic medium using Pd(TPPTS)3 as catalyst yields benzoic acid, which remains in the aqueous phase, thus avoiding the direct recycling of the catalyst [59]. The formation of Pd(TPPTS)3 from PdCl2 and TPPTS in aqueous solution has been studied in detail by 170, 1H 31P, and 35C1 NMR spectroscopy. The complex [ PdCI(TPPTS)3 Cl obtained initially is reduced by excess TPPTS, TPPTSO being formed. A more attractive synthesis of Pd(TPPTS)3 involves the facile reduction of [PdCl-(TPPTS)3]+C1- with CO (Scheme 1) [60],... 

The hydroxycarbonylations (carboxylations) of alkyl, aryl, benzyl and allyl halides are from a retrosynthetic and mechanistic standpoint closely related. This type of reaction is widely used in organic synthesis [6], although a stoichiometric amount of salt by-product makes these methods less attractive on a large scale. The use of water-soluble catalysts for carbonylation of organic halides was scarcely studied in the past. Up to now palladium, cobalt, and nickel compounds in combination with water-soluble ligands have been used as catalysts for various carboxylations. 

Successively, carbon aerogels doped palladium nanoparticles as a recoverable catalyst was applied in the hydroxycarbonylation of aryl iodides by Cacchi and colleagues [144]. Using DMF as a solvent at 100 °C with acetic anhydride/lithium formate along with lithium chloride and DiPEA (MA-dusopropylethylamine) as a base, high to excellent yields can be achieved. The catalyst can be reused up to 12 times without any appreciable loss of activity in the case study of p-iodotoluene. 

Like alkoxycarbonylation, aminocarbonylation, and hydroxycarbonylation, the palladium-catalyzed reductive carbonylation reaction was originally discovered by Schoenberg and Heck in 1974 [15]. In the presence of a relatively large amount of [PdX2(PPh3)2l as a catalyst under 80-100 bar of synthesis gas and at 80-150 °C, aryl and vinyl bromides or iodides were converted into the corresponding aldehydes in good yields (Table 3.1). 

Highly reactive alcohols can serve as substrates for hydroxycarbonylation, which in this case ought to be run in acidic solutions to facilitate the oxidative addition to the C-0 bond. Thus, 5-hydroxymethylfurfural (HMF) was carbonylated to (5-formylfuryl-2)acetic acid using a water-soluble palladium complex with TPPTS ligand as the catalyst at 70°C and 5 bar CO pressure [112] ... 

In the earliest publications [33], it was proposed that the initiation step in both hydroxycarbonylation and polymerization reactions involved the reaction of the alcohol with the palladium complex to give the catalytically active palladium-methoxy complexes. After chain growing reactions, the termination mechanism was supposed to proceed via protonolysis of the alkyl-palladium complex to give the keto-ester (KE) product (methyl propanoate or polymer) and regenerate the active catalyst (Scheme 1.4). In addition, hydrido palladium species are smoothly formed from palladium(II) salts in methanol (not shown). 

Interestingly, the procedure of hydroxycarbonylation by using lithium formate and acetic anhydride as internal condensed sources of carbon monoxide can be carried out in the presence of a recoverable and reusable phosphine-free palladium-carbon aerogel catalyst [61]. To support high-speed chemistry and automated organic synthesis, an operationally simple and environmentally safe hydroxycarbonylation of vinyl triflates can... 

Cacchi, S., Cotet, C.L, Fabrizi, G., Forte, G., Goggiamani, A., Martinez, S., Molins, E., Moreno-Manas, M., Petrucd, F., Roig, A. and VaDribera, A. (2007) Fffident hydroxycarbonylation of aryl iodides using recoverable and reusable carbon aerogels doped with palladium nanopartides as catalyst Tetrahedron, 63, 2519-2523. 

Frew JJR, Damian K, Van Rensburg H, Slawin AMZ, Tooze RP, Clarke ML. Palladium(tf) complexes of new bulky bidentate phosphanes active and highly regioselective catalysts for the hydroxycarbonylation of styrene. Chem. Eur. J. 2009 15 10504-10513. 

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