Reaction alkene hydroformylation

The carbonyl complex [Ru(EDTAH)(CO)] has been reported to be a very good catalyst for reactions like hydroformylation of alkenes, carbonylation of ammonia and ammines as well as a very active catalyst for the water gas shift reaction. The nitrosyl [Ru(EDTA)(NO)] is an oxygen-transfer agent for the oxidation of hex-l-ene to hexan-2-one, and cyclohexane to the corresponding epoxide. 

Stoichiometric model reactions in alkene hydroformylation by platinum-tin systems have been studied for the independent steps involved in the hydroformylation process, insertion of the alkene, insertion of CO, and hydrogenolysis, with use of Pt-Sn catalysts and 1-pentene as alkene at low pressure and temperature.92... 

The less bulky ligand (71) studied by Gladfelter leads to dimeric complexes [Rh2(71)2(CO)2] and even tetramers.222 Transformations of rhodium carbonyl complexes in alkene hydroformylation are discussed from the standpoint of the catalytic system self-control under the action of reaction... 

During a 33 h continuous hydroformylation run using this set-up, no catalyst decomposition was observed and Rh leaching into the scC02/product stream was less than 1 ppm. The selectivity for the linear nonanal was found to be stable over the reaction time with n/iso = 3.1. During the continuous reaction, alkene, CO, H2 and C02 were separately fed into the reactor containing the ionic liquid catalyst solution. Products and unconverted feedstock dissolved in SCCO2 were removed from the ionic liquid. After decompression the liquid product was collected and analysed. 

The synthesis of aldehydes via hydroformylation of alkenes is an important industrial process used to produce in the region of 6 million tonnes a year of aldehydes. These compounds are used as intermediates in the manufacture of plasticizers, soaps, detergents and pharmaceutical products [7], While the majority of aldehydes prepared from alkene hydroformylation are done so in organic solvents, some research in 1975 showed that rhodium complexes with sulfonated phosphine ligands immobilized in water were able to hydroformylate propene with virtually complete retention of rhodium in the aqueous phase [8], Since catalyst loss is a major problem in the production of bulk chemicals of this nature, the process was scaled up, culminating in the Ruhrchemie-Rhone-Poulenc process for hydroformylation of propene, initially on a 120000 tonne per year scale [9], The development of this biphasic process represents one of the major transitions since the discovery of the hydroformylation reaction. The key transitions in this field include [10] ... 

In Figure 4.2 we have drawn how we can distinguish the two faces of an alkene, or rather the side of attack of a specific atom of the alkene. The arrow on the left approaches the lower carbon of the alkene and when looking from this viewpoint we count the weight of the three substituents the same way as in the CIP rules. We then see the order 1, 2, and 3 counter-clockwise, and we say that the arrow approaches the carbon atom from the si face. For simplicity we call this the si face of the alkene and in most cases this will do. If all four substituents at the alkene are different we can determine the re/si properties of both carbon atoms and these may be different This results in the nomenclature that an alkene may have a re,re and si,si face or re,si and si,re face. Thus, in the latter case one has to indicate to which atom the label is referring. For any enantiospecific, catalytic reaction (hydrogenation, hydroformylation, polymerisation) it is very convenient to use the re and si indicators in the discussion. 

In general, the mechanism of alkene hydroformylation with an [RhH(CO)P3] catalyst in water or in aqueous/organic biphasic systems (P = TPPTS) is considered to be analogous [61] to that of the same reaction in homogeneous organic solutions (P = PPh3) [84], a basic version of which is shown on Scheme 4.8. 

Pronounced rate and selectivity enhancements had previously been observed for Ni(0)-catalyzed cyclodimerizations as well as rhodium-catalyzed alkene hydroformylation reactions. For related references see (Ni) van Leeuwen, P.W.N.M. Roobeek, C.F. Tetrahedron 1981, 37, 1973. (Rh) van Leeuwen,... 

A number of ruthenium-based catalysts for syn-gas reactions have been probed by HP IR spectroscopy. For example, Braca and co-workers observed the presence of [Ru(CO)3l3]", [HRu3(CO)ii]" and [HRu(CO)4] in various relative amounts during the reactions of alkenes and alcohols with CO/H2 [90]. The hydrido ruthenium species were found to be active in alkene hydroformylation and hydrogenation of the resulting aldehydes, but were inactive for alcohol carbonylation. By contrast, [Ru(CO)3l3]" was active in the carbonylation of alcohols, glycols, ethers and esters and in the hydrogenation of alkenes and oxygenates. 

The generation of a chiral center as a result of alkene hydroformylation can take place either by formylation or hydride addition at the prochiral carbon (equations 30 and 31). Kinetic resolution in the hydroformylation reaction of a racemic alkene containing a chiral center could also occur, but in this example the chiral center is not generated as a result of the hydroformylation reaction. 

Another important reaction typically proceeding in transition metal complexes is the insertion reaction. Carbon monoxide readily undergoes this process. Therefore, the insertion reaction is extremely important in organoiron chemistry for carbonylation of alkyl groups to aldehydes, ketones (compare Scheme 1.2) or carboxylic acid derivatives. Industrially important catalytic processes based on insertion reactions are hydroformylation and alkene polymerization. 

A number of metals catalyze the hydroformylation reaction, of which rhodium is by far the most active, Rh >> Co > Ir, Ru > Os > Pt. Platinum and ruthenium are mainly of academic interest, although L2PtCl(SnCl3) complexes with chiral ligands find use in asymmetric alkene hydroformylations.59 In most cases, and certainly in industrial processes, cobalt has now been replaced by rhodium. 

The proposed mechanism is shown in Scheme 25. The coupling of this reaction with hydroformylation, for example, allows the conversion of an alkene directly into an N-acetyl product. Thus, the reaction of trifluoropropylene and acetamide produces A-acetyltrifluoronorvaline in 80% yield with 96% selectivity. 

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