Hydroformylation Palladium-carbon

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... 

Asymmetric hydrocarbalkoxylation of alkenes has been studied since the early 1970s, but the number of papers published on this subject is much less than that of asymmetric hydroformylation. This difference is mainly due to the fact that these reactions catalyzed by palladium complexes with chiral phosphine ligands usually require a very high pressure of carbon... 

Catalytic formation of carbon-carbon bonds is a powerful tool for construction of complex molecular architectures, and has been developed extensively for applications in organic synthesis. Three main classes of carbon-carbon bond forming reactions have been studied in sc C02 carbonylation (with particular attention paid to the hydroformylation of a-olefins), palladium-catalyzed coupling reactions involving aromatic halides, and olefin metathesis. 

The group of Van Leeuwen has reported the synthesis of a series of functionalized diphenylphosphines using carbosilane dendrimers as supports. These were applied as ligands for palladium-catalyzed allylic substitution and amination, as well as for rhodium-catalyzed hydroformylation reactions [20,21,44,45]. Carbosilane dendrimers containing two and three carbon atoms between the silicon branching points were used as models in order to investigate the effect of compactness and flexibility of the dendritic ligands on the catalytic performance of their metal complexes. Peripherally phosphine-functionalized carbosilane dendrimers (with both monodentate... 

Another commercial aldehyde synthesis is the catalytic dehydrogenation of primary alcohols at high temperature in the presence of a copper or a copper-chromite catalyst. Although there are several other synthetic processes employed, these tend to be smaller scale reactions. For example, acyl halides can be reduced to the aldehyde (Rosenmund reaction) using a palladium-on-barium sulfate catalyst. Formylation of aryl compounds, similar to hydroformylation, using HCN and HC1 (Gatterman reaction) or carbon monoxide and HC1 (Gatterman-Koch reaction) can be used to produce aromatic aldehydes. 

Two examples are highlighted below where precious metal catalysts are used to produce fine chemicals on an industrial scale via carbon-carbon bond forming reactions. The first (a) is rhodium-catalysed hydroformylation in the oxo-process , which is a well established industrial process. The second (b) highlights a new process developed by Lucite involving a palladium-catalysed methoxy-carbonyla-tion. Many of the points mentioned above in this article are illustrated in the examples, with efficient recycle of catalyst (precious metal) and the extra cost of ligands being justified by the costs savings of the novel chemistry. 

Several important homogeneous catalytic reactions (e.g. hydroformylations) have been accomplished in water by use of water-soluble catalysts in some instances water can act as a solvent and as a reactant for hydroformylation. In addition, formation of aluminoxanes by partial hydrolysis of alkylaluminum halides results in very high activity bimetallic Al/Ti or Al/Zr metallocene catalysts for ethene polymerization which would be otherwise inactive. Polymerization of aryl diiodides and acetylene gas has recently been achieved in water with palladium catalysts. Finally, nickel-containing enzymes, such as carbon monoxide dehydrogenase (CODH) and acetyl-CoA synthase, operate in water with reaction mechanisms comparable with those of the WGSR or of the Monsanto methanol-to-acetic-acid process. ... 

Cuprous chloride tends to form water-soluble complexes with lower olefins and acts as an IPTC catalyst, e.g., in the two-phase hydrolysis of alkyl chlorides to alcohols with sodium carboxylate solution [10,151] and in the Prins reactions between 1-alkenes and aqueous formaldehyde in the presence of HCl to form 1,3-glycols [10]. Similarly, water-soluble rhodium-based catalysts (4-diphenylphosphinobenzoic acid and tri-Cs-io-alkylmethylam-monium chlorides) were used as IPTC catalysts for the hydroformylation of hexene, dodecene, and hexadecene to produce aldehydes for the fine chemicals market [152]. Palladium diphenyl(potassium sulfonatobenzyl)phosphine and its oxide complexes catalyzed the IPTC dehalogenation reactions of allyl and benzyl halides [153]. Allylic substrates such as cinnamyl ethyl carbonate and nucleophiles such as ethyl acetoactate and acetyl acetone catalyzed by a water-soluble bis(dibenzylideneacetone)palladium or palladium complex of sulfonated triphenylphosphine gave regio- and stereo-specific alkylation products in quantitative yields [154]. Ito et al. used a self-assembled nanocage as an IPTC catalyst for the Wacker oxidation of styrene catalyzed by (en)Pd(N03) [155]. 

A number of other materials were reported to act as promoters, such as zinc [110, 337], magnesium [111], aluminum [111], bismuth [112], lead [112], gold [112], mercury salts [112], palladium zeolite [113], activated carbon [45] and iron carbonyl [171,979]. Some of these materials were reported to accelerate the hydroformylation but suppress the hydrogenation of the aldehydes formed. 

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