Reppe hydroformylation

The C0/H20 systems have been used to catalyze hydrogenation of olefins in Reppe hydroformylation 437), and a Rh6(CO)16-catalyzed system has been used to reduce the olefinic bond in a,/3-unsaturated carbonyls and nitriles 337, 338, Section IV,A). 

In presence of diphos, [Co2(CO)8] catalyzes the reaction of propylene with CO and H20 to give aldehydes (Reppe hydroformylation, equation 80).406 The reaction requires high temperature... 

As a matter of fact, a kind of hydroformylation can also be obtained with carbon monoxide and water using, for example, Fc(CO)s in alkaline conditions as the catalyst (the so-called Reppe hydroformylation)... 

The Reppe hydroformylation of ethylene to produce propionaldehyde and 1—propanol in basic solutions containing Fe(CO)5 as a catalyst was studied under carefully controlled conditions at a temperature range of 110—140°C. Propionaldehyde is the main product formed when NaOH is used as the base. The reaction is shown below ... 

The advances in the hydroformylation of olefins carrying functional groups have been summarized in a review which stresses the potential of hydroformylation for the production of fine chemicals and high value-added products. The kinetics of the Reppe hydroformylation of ethylene catalyzed by [Fe(CO)s] at 110-140 °C in basic solution have been determined. Propionaldehyde and propanol... 

In alkaline solution of an iron-carbon monoxide complex, the alkenes are converted into aldehydes and finally alcohols of one more carbon atom. Under these conditions, the iron complex of carbon monoxide was found to be binuclear, whereas the mononuclear complex is labile at temperatures above 140°C. In addition, it has been found that aldehyde is an initial product that is reduced to alcohol in the second stage of the reaction, and the nature of the base plays an important role in controlling the reaction path, either to produce aldehyde (e.g., KOH) or alcohol (e.g., alkyl amines).The formation of aldehyde is known as Reppe hydroformylation or the Reppe reaction. ... 

Ma.nufa.cture. Most butanediol is manufactured in Reppe plants via hydrogenation of butynediol. Recendy an alternative route involving acetoxyiation of butadiene has come on stream and, more recendy, a route based upon hydroformylation of allyl alcohol. Woddwide butanediol capacity has climbed steadily for many years. In 1990 it was estimated to be 428,000 metric tons (141), as compared to a Htde more than 70,000 metric tons in 1975... 

The hydroformylation reaction has been the subject of excellent reviews (for example I, 6-8) therefore, the object of this particular treatise is not to provide comprehensive coverage of all aspects. The basic chemistry is presented, along with recent developments of interest as reported in the literature, although not in chronological order. Stereochemical studies (6) are included only when pertinent to another point under consideration. Carbonylations or hydrocarboxylation reactions which produce ketones, esters, acids, esters, or amides are not included (/). Also not included is the so-called Reppe" synthesis, which is represented by Eq. (1). 

Pettit and coworkers—metal hydride intermediates by weak base attack over Fe carbonyl catalysts. Pettit et al.ls approached the use of metal carbonyl catalysts for the homogeneous water-gas shift reaction from the standpoint of hydroformyla-tion by the Reppe modification.7 In the typical hydroformylation reaction, an alkene is converted to the next higher aldehyde or alcohol through reaction of CO and H2 with the use of a cobalt or rhodium carbonyl catalyst. However, in the Reppe modification, the reduction is carried out with CO and H20 in lieu of H2 (Scheme 6) ... 

For this reaction, the early investigations of Reppe pointed out the need for catalyst precursors to operate at high pressure [2], It is necessary to work at 150-300 bar of CO in order to stabilize the two catalytic species [Co(H)(CO)4] or [Ni(H)(X)(CO)2] that adopt a mechanism analogous to the cobalt-catalyzed hydroformylation [44,45]. Many industrial applications have been reported [28,46,47] for the synthesis of plasticizers and detergents. Similarly, the two-step methoxycarbonylation of 1,3-butadiene has been explored by BASF and other companies to produce dimethyl 1,6-hexanedioate (adipate) directly from the C4 cut [28,48]. The first step operates at 130 °C and... 

Reactions of Alkenes and Alkynes in Presence of Metal Carbonyls. Metal carbonyls—e.g., Ni(CO)4, Fe(CO)5, and Co2(CO)s—and hydrocarbonyls— HCO(CO)4 and H2Fe(CO)4—act as catalysts for the transformation of simple unsaturated materials into a wide variety of larger molecules. Perhaps the simplest example is that of hydroformylation (Equation 7). Reppe chemistry... 

Metal-catalyzed reactions of CO with organic molecules have been under investigation since the late 1930s and early 1940s, when Roelen (/) discovered the hydroformylation reaction and Reppe (2) the acrylic acid synthesis and other related carbonylation reactions. These early studies of the carbonyla-tions of unsaturated hydrocarbons led to extremely useful syntheses of a variety of oxygenated products. Some of the reactions, however, suffered from the serious problem that they produced isomeric mixtures of products. For example, the cobalt-catalyzed hydroformylation of propylene gave mixtures of n-butyraldehyde and isobutyraldehyde. 

One may improve efficiency of an o-DPPB directed hydroformylation by incorporating this reaction into sequential transformations (domino reactions) [16]. The hydroformylation itself should be ideally suited for such a purpose, since this reaction provides under fairly mild reaction conditions access to the synthetically valuable aldehyde functionality. The aldehyde itself should be ideally suited to allow for further skeleton-constructing reactions. One type of sequential transformations employing the hydroformylation reaction as a key step is the hydroaminomethylation of olefins originally discovered by Reppe [17]. However, efficient control of diastereoselectivity in the course of this hydroaminomethylation reaction was unknown [18, 19]. 

Hydroaminomethylation is a promising reaction to functionalize unsaturated compounds with an amino group [13, 48, 49], The tandem reaction was discovered by Reppe in 1949 and has been further developed in recent years by Eilbracht and Beller. Hydroaminomethylation consists of three consecutive reactions which are carried out in the same reaction vessel [48], The first reaction is hydroformylation which is followed by the condensation with an amine. Hydrogenation of the generated enamine/imine to the amine is the last step. The conditions for hydroaminomethylation are related to the hydroformylation reaction but are not similar due to the two other reactions. The reaction is called an auto-tandem reaction because two of the three reactions need the same catalyst [9] (Scheme 16). 

In 1941 Reppe demonstrated the potential of many metal carbonyls in several reactions including hydroformylation. This work resulted in 1960 in a process based on C0I2 operating at 700 bar and 250°C. Corrosion problems were overcome by applying Hastelloy C. 

A great variety of reactions with CO are known and have gained industrial importance. Best known is the Roclen-synthesis (hydroformylation or 0x0-synthesis) by whicli about 5 million tons of aldehydes, acids and alcohols are synthesized worldwide. But also carbonylailons (Reppe reaction) are practised in many plants. Carbonylations are those reactions in which CO. alone or together with other compounds, is introduced into particular derivatives exemplified in the following reactions ... 

After discussing in detail the specific aspects of Reppe s chemistry and of hydroformylation and related reactions, it is quite interesting to examine the general mechanistic implications of these two types of reactions. 

The production of carboxylic acids via carbonylation catalysis is the second most important industrial homogeneous group of processes. Reppe developed most of the basic carbonylation chemistry in the 1930s and 1940s. The first commercial carbonylation process was the stoichiometric Ni(CO)4-based hydroxycarbonylation of acetylene to give acrylic acid (see Section 3.5 for details). This discovery has since evolved into a trae Ni-catalyzed process, used mainly by BASF. The introduction of rhodium catalysts in the 1970s revolutionized carboxylic acid production, particularly for acetic acid, much in the same way that Rh/PPhs catalysts changed the importance of hydroformylation catalysis. 

B. Comils, Hydroformylation , A. MuUen, Reppe Chemistry , and A. Mullen, Ring Closure Reactions with CO, in New Syntheses with Carbon Monoxide , ed. J. Falbe, Springer-Verlag, Berhn, 1980. 

Two research groups have explored the use of the CO/H2O couple instead of CO/H2 in the hydroformylation reaction. In fact, this reaction was discovered by Reppe using [Fe(CO)5] (/) and requires the presence of a base to produce hydrido species. Investigation of this reaction by Pettit e/ al. 41) has shown that the two hydrido iron species are formed [eq. (10)] ... 

W. Reppe / BASF (> 1938) catalytic transformations of alkynes 0. Roelen / RUHRCHEMIE (1938) hydroformylation... 

The use of CO + HjO as an in situ source of H2 via the shift reaction or as a source of reducing electrons with concomitant oxidation of CO to CO2 has recently been explored with homogeneous catalyst solutions. Equations (a) and (b) are modifications (Reppe) of hydroformylation (see 14.6.3) and olefin hydrogenation, respectively. The most effective catalysts for equation (a) are Ru3(CO),2, Rh fCOlig, Ir4(CO)i2 in alkaline THE or MeOH. The first of these shows great selectivity in the formation of linear vs. branched aldehyde . With Rhg(CO),5, the aldehyde is reduced further to the alcohol. A different catalyst based on Co2(CO)g/diphos in polar ether solvents has also been used to catalyze equation (a) with propylene as substrate. ... 

Commercial petrochemical processes using syngas or carbon monoxide are based on four principal classes of reactions phosgenation, Reppe chemistry, hydroformylations, and Koch carbonylations. Phosgenation is a key step in the manufacture of polyurethanes, polycarbonates, and monoisocyanates. Reppe chemistry is the basis for acetic acid and acetic anhydride production as well as formic acid and methyl methacrylate synthesis. Hydroformylations utilize syngas in the oxo synthesis to make a wide variety of aldehydes and long-chain alcohols. The fourth class of reactions are Koch carbonylations. Koch carbonylations are used commercially to produce neo acids which are specialty products that serve markets similar to 0X0 alcohols. 

The term carbonylation was first used by W.Reppe while working with syngas and carbon monoxide chemistry at BASF during the 1930s and 1940s. Carbonylations are catalytic reactions in which carbon monoxide, alone or with other compounds, is incorporated in an organic substrate. There are three general types of carbonylation reactions Reppe reactions, hydroformylations, and Koch carbonylations. 

Hydroformylation is the reaction of carbon monoxide and hydrogen with olefins to produce aldehydes and derivative alcohols. It is also known as 0X0 chemistry and the alcohol products produced by this method are known as 0X0 alcohols. Of all three types of carbon monoxide reactions, Reppe reactions, Koch carbonylations, and hydroformylations, oxo chemistry currently has the greatest commercial importance. An extremely broad range of products and end use markets are served by the aldehydes, alcohols, and derivatives produced by hydroformylation. The list of products shown in Table 6 illustrates the range of oxo chemical products. 

Our initial efforts in the area of reductions with CO + H2O involved a study of the mechanism of what we shall term the Reppe modification of the hydroformylation reaction (3). In the normal hydroformylation process, the elements of hydrogen and CO are added to an olefin to generate an aldehyde (Reaction 3). In the Reppe modification of this process, the same reaction is achieved using CO + H2O in place of hydrogen (Reaction 4). In the normal process, the catalyst used is usually a... 

We consider then that the mechanism of the Reppe modification of the hydroformylation reaction closely parallels that of the normal process as described by Heck and Breslow (JO). The principal steps are given in the following scheme ... 

The normal hydroformylation reaction and the Reppe modification are mechanistically closely related the key point which emerges is that in the latter process it is easier to form the species H2Fe(CO)4 from the reaction of Fe(CO)5 and aqueous base than it is from Fe(CO)5 and molecular hydrogen. For this reason, the combination of CO-f-H2O provides a superior reducing system for the reductive addition of CO to an olefin than does molecular hydrogen. 

Other Metal Catalysts. - Hydroformylation catalysts containing Co and Rh have been known for many years and these metals are the only catalysts used industrially. Recently two catalyst systems have been developed that have certain advantages over the conventional catalysts. Pt/Sn chloride complexes show very high selectivity to n-aldehyde. and Reppe-type systems which hydroformylate alkenes in the presence of CO/H2O rather than CO/H2. ... 

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