Olefins homogeneous hydroformylation

Homogeneous Hydroformylation of Olefins in the Presence of Chiral Rhodium(I)-Phosphine Catalysts... 

It has yet to be seen whether the principle of biphasic hydroformylation can be further extended beyond C4 olefins. Bearing in mind the advantages of biphasic operation, two pathways may be considered biphasic operation in the reactor section and subsequent phase separation or a combination of homogeneous hydroformylation reaction with an auxiliary agent. This substance would require a miscibility gap with the products under conditions different from the reaction conditions. Examples of both principal methods have already been published [271, 272]. However, a general solution is not to be expected, as each feed-stock/product pair requires a specially adapted solvent. Novel developments in the field of catalyst separation and reuse of catalyst systems are noted below. 

The homogeneous hydroformylation could take place both in conventional and environmentally benign (green) reaction media. The solubility of the catalyst is primarily determined by the applied ligand due to its polarity and/or functionality. The unmodified catalysts can be dissolved in the hydrocarbons such as alkanes and toluene, or in industrial scale the reaction is performed in the crude olefin mixtures (downstream) containing different unsaturated hydrocarbons. The solubility of the modified catalyst in the alternative reaction media is easily affected by the ligand variation of the metal complex for example... 

Tang, S.C. and Kim, L. (1982) Homogeneous hydroformylation of internal olefins by platinum tin cationic complexes. Journal cf Molecular Catalysis. 

A new homogeneous process for hydroformylation of olefins using a water-soluble catalyst has been developed (40). The catalyst is based on a rhodium complex and utilizes a water-soluble phosphine such as tri(M-sulfophenyl)phosphine. The use of an aqueous phase simplifies the separation of the catalyst and products (see Oxo process). 

The industrially used homogeneous catalysts for the hydroformylation of higher molecular olefins into aldehydes, which are hydrogenated to the corresponding surfactant alcohols, are cobalt carbonyl [47] or cobalt carbonylItert-phosphine complexes [48]. 

Much of the recent interest in insertion reactions undeniably stems from the emphasis placed on development of homogeneous catalysis as a rational discipline. One or more insertion is involved in such catalytic processes as the hydroformylation (31) or the polymerization of olefins 26, 75) and isocyanides 244). In addition, many insertion reactions have been successfully employed in organic and organometallic synthesis. The research in this general area has helped systematize a large body of previously unrelated facts and opened new areas of chemistry for investigation. Heck 114) and Lappert and Prokai 161) provide a comprehensive compilation and a systematic discussion of a wide variety of insertion reactions in two relatively recent (1965 and 1967) reviews. 

Hydroformylation represents the most industrially important homogeneous catalysed reaction by volume [2, 3]. The petrochemical, agrochemical and pharmaceutical industries are particularly interested in this transformation. The reaction uses syngas (COiH mix) and a catalyst, commonly rhodium or platinum, to transform an olefin into an aldehyde (Scheme 9.1) [4]. 

Comparing heterogeneous Fischer-Tropsch synthesis with homogeneous olefin hydroformylation can be seen as a source for understanding catalytic principles, particularly because the selectivity is complex and therefore highly informative. Reliable analytical techniques must be readily available. 

Optically active aldehydes are important precursors for biologically active compounds, and much effort has been applied to their asymmetric synthesis. Asymmetric hydroformylation has attracted much attention as a potential route to enantiomerically pure aldehyde because this method starts from inexpensive olefins and synthesis gas (CO/H2). Although rhodium-catalyzed hydrogenation has been one of the most important applications of homogeneous catalysis in industry, rhodium-mediated hydroformylation has also been extensively studied as a route to aldehydes. 

The hydroformylation reaction that converts olefins into aldehydes is the largest volume homogeneous transition-metal catalyzed reaction used today. This reaction has been extensively studied and nowadays a number of efficient catalysts make it possible to control the regioselectivity of the reaction to give terminal or internal aldehydes (Scheme 1). 

Hydroaminomethylation is a simple, efficient and atom-economic method to synthesize various amines. This one-pot reaction consists of three consecutive steps in the first step a hydroformylation of an olefin is performed followed by the reaction of the resulting aldehyde with a primary or secondary amine to give the corresponding enamine or imine. Lastly, this intermediate is hydrogenated to the desired secondary or tertiary amine (Fig. 11) [33-39]. In most cases rhodium salts or complexes are used as the homogeneous catalyst in the hydroaminomethylation. 

The hydroformylation of olefins discovered by Otto Roelen [ 151 ] is one of the most important industrial homogeneously catalyzed reactions [152,153] for the synthesis of aldehydes with an estimated production of more than 9.2 million t in 1998 [ 153]. Hydroformylation is the addition of hydrogen and carbon monoxide to a C,C double bond. Industrial processes are based on cobalt or rhodiiun catalysts according to Eq. 1. The desired products are linear (n-) and branched (i-) aldehydes, in which the hnear products are generally favored for subsequent processing. 

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