Hydroesterification palladium catalyst

In a manner similar manner, the hydrocarbalkoxylation (commonly called hydroesterification) of alkenes in the presence of alcohols can be effected by the nickel, cobalt, platinum, and palladium catalysts described above (Eq. 

Up to now, palladium complexes do not play a significant role in the hydroformylation of olefins [1]. However, because of their widespread use in the related hydrocarboxylation, hydroesterification, and olefin copolymerization with CO [2], occasionally their utility for hydroformylation was elucidated [3]. Moreover, palladium catalysts have been used for the hydroformylation of aryl and enol triflates to produce the corresponding unsaturated aldehydes [4]. 

Highly active, selective, and recyclable palladium catalyst systems for the hydroesterification of styrene (at room temperature and 6 bar CO pressure) and vinyl acetate (at 40-60 °C and 6-10 bar CO pressure) were found by using l,2-bis(di-tert-butylphosphinomethyl)benzene as ligand and polymeric sulfonic adds of limited SO3H loadings as promoter [148]. 

With the tandem catalyst Pd/Sn, the hydroesterification of limonene delivered a 90% yield of the linear product, while in the absence of tin, more branched esters were formed. The hydroesterification of camphene delivers the linear product with a selectivity of 90%, whereas the two diastereomers were built in an equal ratio. The additive SnCl2 had a high impact on catalytic activity without this additive, the palladium/diphosphinobutane catalyst had lower activity. 

A useful synthesis of ( )-j -ethoxycarbonylvinylsilanes by palladium-catalyzed regio- and stereospecific hydroesterification (EtOH -I- CO) (or carboethoxylation) of trimethylsilylacetylenes has been reported recently [210]. Alkoxycarbonyl or carbonyl functionalization of vinylsilanes are useful synthetic intermediates [211, 212]. The use of PdCl2(dppf) as a catalyst (with SnCl2 2 H2O as cocatalyst) is found to be superior and gives excellent yields. A key step in the reaction is thought to involve hydropalladation to give 60 or 61. The preference for 60 to 61 is understood... 

Support for the involvement of HPdCl(PPh3)2 as the active species in palladium-catalyzed hydroesterifications comes from the isolation of frans-Pd-(COPr)Cl(PPh3)2 from propene hydroformylation [5], while Pd(CO)(PPh3)3 is inactive as a catalyst in the absence of HCI [6]. In the case of PdX2L2/SnX2 catalyst systems olefins seem to be the hydrogen source for the formation of the active Pd-H species [7],... 

As mentioned earlier, palladium, rhodium, and platinum catalysts lead to superior regioselectivities because they work under milder reaction conditions (20-80 °C, 0.1-1 MPa CO) [11], e.g., bimetallic catalysts based on tin(II) chloride and either platinum or palladium complexes afford linear esters in up to 98 % selectivity [12]. In addition, catalyst systems with preference for branched isomers are known. A recent example employed palladium acetate immobilized on montmorillonite in the presence of triphenylphosphine and an acid promoter for the hydroesterification of aryl olefins (eq. (3)). The reaction is totally regiospecific for the branched isomer of aromatic olefins, while aliphatic olefins afford branched chain esters only regioselectively with n/i = 1 3 [13]. 

Alkynes undergo simple hydroesterification under mild conditions to give a,B-unsatuiated esters. Addition of the ester function to terminal alkynes frequently occurs at the substituted carbon atom to give branched products, but linear esters may be obtained witfi high selectivity using palladium-tin catalysts (equation 36). Under oxidative carbonylation conditions cir-diesters are formed. ... 

Iridium with tributylphosphine like Co and Ru, is inferior to Rh as an ethylene hydroesterification catalyst. Palladium acetate gives no reaction. Propylene and other higher olefins react extremely slowly, even under optimum Rh tributylphosphine catalytic conditions. 

Hydrocarboxylation is the formal addition of hydrogen and a carboxylic group to double or triple bonds to form carboxylic acids or their derivatives. It is achieved by transition metal catalyzed conversion of unsaturated substrates with carbon monoxide in the presence of water, alcohols, or other acidic reagents. Ester formation is also called hydroesterification or hydrocarb(o)alkoxylation . The transition metal catalyst precursors are nickel, iron or cobalt carbonyls or salts of nickel, iron, cobalt, rhodium, palladium, platinum, or other metals4 5. 

One can also envision that the quinone could trap the hydridopalladium species resulting from the B-hydrogen elimination that releases the oxidized organic product (Equation 16.129). Insertion of quinone into the palladium hydride would form an enolate that would tautomerize to the phenoxide complex. Protonation with the reagent containing an 0-H or N-H bond would generate the free hydroquinone and Pd(II). As noted in Chapter 17 on carbonylation, quinone has been used as an additive with this mechanism in mind to prevent tire Pd(II) hydroesterification catalysts from undergoing reduction to palladium(O). ... 

The hydroesterification of alkynes (Equation 17.45) was first conducted with Ni(CO) as catalyst to produce acrylate esters as products. Much more active catalysts for this reaction have now been generated from a combination of palladium acetate and 2-pyridylphosphines. The use of these ligands for alkyne hydroesterification was conducted by Drent at Shell. 

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