Carbonylation hydroesterification

E.2. Supported Dendritic Catalysts for Carbonylation, Hydroesterification, Oxidation, and Heck Reactions... 

The insertion of CO into a C(sp )-Pd or C(sp )-Pd species is a common procedure and it is applicable to a wide range of reactions, such as hydroformylation, carbonylation, hydroesterification and so on, thus being an ideal terminating transformation within a domino process starting, for example, with a Mizoroki-Heck reaction. 

In the reaction of aHyl alcohol with carbon monoxide using cobalt carbonyl, Co(CO)g as the catalyst, in the presence of a small amount of hydrogen and carbon monoxide under pressure, 9.8 MPa (1420 psi), at 100°C, intramolecular hydroesterification takes place, yielding y-butyrolactone [96-48-0] (16). 

Hydro carbonylation of olefins, hydroformylation, hydroesterification and hy-droxycarbonylation are reactions which appear to be of particular interest. Indeed, they allow the simultaneous creation of a new C - C bond as well as the introduction of a functional group (aldehyde, ester and acids). One or two new stereogenic centres can thus be formed at the same time (Scheme 26). Despite the difficulty of using high carbon monoxide pressure, the aheady existing industrial processes prove that such reactions can be performed on a very large scale [107]. 

In presence of a mild base such as Na2C03 or NaOAc, a hydroesterification to furanones is possible (equation 89).437 RhCl3-3H20 or a binary carbonyl was used as catalyst. Indanont derivatives were obtained as by-products. The mechanism probably involves the formation of ar alkoxycarbonyl intermediate (Scheme 29). 

The hydroesterification of dienes gave both the unsaturated monoesters and saturated diesters.524 In some cases, y-ketoesters were obtained and carbonylation of 1,5-cyclooctadiene in absence of alcohol gave a ketone.525 [PdI2(PBu3)2] was used as catalyst. If the catalyst contained a halide anion, butadiene underwent normal hydroesterification. When halide-free catalysts were used, the reaction took a different course. Dimerization of the diene occurred to give the ester of 3,8-nonadienoic acid as the major product (equation 128).526-528... 

Platinum complexes have so far proved to be of only limited value as carbonylation catalysts. H2PtCl6 in the presence of SnCl2 acts as a hydroesterification catalyst for terminal alkenes (equation 141).5... 

So far, very little work has been carried out on asymmetric carbonylation. Existing studies all concern the hydroesterification of alkenes (equation 145). Depending on the structure of the alkene and the regioselectivity of the reaction, one or two asymmetric carbon atoms may be present in the product (equation 145).S74... 

The regioselectivity of carbonylation of vinylsilanes appears to depend on the nature of the catalysts. Thus, the PdCl2(PPh3)2-catalyzed hydroesterification of vinylsilanes... 

The cycle is started with the formation of a Pd-alkoxy complex that reacts with CO to an alkoxycarbonyl intermediate. In the next step, the approach of the olefin and insertion into the carbonyl palladium bond is predicted. In the last step, the starting complex is rebuilt by the addition of an alcohol and the cleavage of the hydroesterification product [59]. 

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... 

Many other addition reactions of olefins, dienes, and acetylenes are known, which are catalyzed by metal carbonyls including Ni(CO)4, Fe(CO)5, and Co2(CO)8 and by carbonyl derivatives such as hydrocarbonyls or phosphine-substituted carbonyls. Among these are the hydro-carboxylation, hydroesterification, and hydrocyanation of olefins the synthesis of hydroquiniones from acetylenes, carbon monoxide, and water ... 

Rhodium cationic and zwitteiionic complexes proved to be superior catalysts for the hydroformylation of vinylsilanes, producing either a- or ff-silyl aldehydes depending on the reaction conditions [162], On the other hand, carbonylation of vinylsilanes in the reaction related to hydrocarboxylation and hydroesterification afforded P- and a-silyl esters in high yields (eq. (14) [163]). 

The synthesis of an ester by addition of carbon monoxide and an alcohol to an alkene, i.e. hydroesterification, has a fairly obvious relationship to the hydrocarboxylation described in Section 4.1.5, where water replaces the alcohol and a carboxylic acid is formed. Not surprisingly, therefore, the same types of catalysts, [Co2(CO)s], [H2PtCl6] and [Pd(PPh3)2Ch], are effective for both reactions. Unfortunately, the reaction usually requires very high pressures (200 bar) and necessitates the use of an autoclave. By varying the catalyst and reaction conditions a variety of linear, branched and cyclic alkenes can be carbonylated under these conditions to give the product in good yield (equation 32). Improved selectivity to the linear ester can be obtained by addition of SnCU to the catalyst system. 

Palladium salts can bring about oxidative carbonylation of alkenes in the presence of copper(II) salts which can reoxidize Pd° to Pd . Oxidative carbonylation is favored over simple hydroesterification by the presence of bases and by low temperatures (25 C) and low pressures (3-15 bar). The products can be a, -unsaturated esters, dicarboxylic acid esters or -alkoxy esters. By careful optimization of the conditions (25 °C, 4 bar CO, methanol solvent, CuCh reoxidant and sodium butyrate buffer) high yields of diesters can be obtained (equation 35). ... 

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. ... 

Carbonylation of olefins in the presence of alcohols to give esters is called hydroesterification. Similarly, olefin carbonylation in the presence of carboxylic acids yields acid anhydrides. Both hydroesterification and acid anhydride formation by olefin carbonylation are covered in section 14.6.4. Other carbonylation variations, including the use of acetylenic substrates, thiols and amines as hydrogen sources and the carbonylation of allylic halides are not discussed. Several excellent reviews of hydrocarboxyiation and carbonylation of olefinshave appeared. 

Early hydrocarboxylation-hydroesterification literature deals largely with Ni and Co as activating metals, but during the last three decades the noble group VIII metals, especially Pd, Pt, Rh and Ir, have been studied. Similarly, the use of pyridine promoted Co catalysts has been optimized. This section will not include references to metals of lesser or more specialized activity, such as Fe, Ru and Cu(I), nor strong acid catalysis, nor oxidative carbonylation of alkanes. 

Cobalt is the catalyst most widely employed for hydrocarboxylations and hydroesterifications. The strong similarity to hydroformylation is shown in the catalyst and in the conditions of T and P. In general the three process rates are in the order hydrofor-mylation>hydrocarboxylation>hydroesterification. Like hydroformylation, the high P of CO required, the instability and toxicity of cobalt carbonyl or hydrocarbonyl and the difficulty of catalyst-product separation detract from the overall attractiveness of this reaction . 

The use of CO containing 3% H2 in the hydroesterification reaction is standard, suggesting that a cobalt hydrocarbonyl is the active catalyst species. The reaction sequence involves olefin insertion into the Co—H bond, (carbonyl insertion) to give an acyl complex and cleavage with alcohol assisted by the pyridine promoter ... 

As with Co, Rh and Ir catalyze the olefin carbonylation reactions of hydrocarboxylation, hydroesterification and acid anhydride formation. Rhodium or Ir complexes and iodide promoters with HjO as the hydrogen source yields a mixture of linear and branched carbocylic acids the branched isomer predominates. Many soluble complexes, such as Irlj, Ir2(CO)4Br2, Rh(PPh3)2(CO)Cl or Ir[(C4H9)3P](CO)I can be utilized as a solution in a carboxylic acid solvent. The iodide source can be HI or any material which... 

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