Reppe reaction conditions

Another catalytic application emanating from the Hieber base reaction was developed by Reppe and Vetter [108]. They showed that 1-propanol 126 could be generated by treatment of ethylene 125 with catalytic amounts of Fe(CO)5 78 under CO-pressure and basic reaction conditions (Scheme 33). Thereby, trimethylamine and V-alkylated amino acid derivatives mrned out to be optimal bases for this reaction. Like ethylene 125, propylene could be transferred mainly to 1-butanol diolefins like butadiene only reacted to monoalcohols. By employing these reaction conditions to olefins in the presence of ammonia, primary or secondary amines, mono-, di-, and trialkylamines were obtained whose alkyl chains were elongated with one carbon atom, compared to the olefins. 

Reppe reaction involves carbonylation of methanol to acetic acid and methyl acetate and subsequent carbonylation of the product methyl acetate to acetic anhydride. The reaction is carried out at 600 atm and 230°C in the presence of iodide-promoted cobalt catalyst to form acetic acid at over 90% yield. In the presence of rhodium catalyst the reaction occurs at milder conditions at 30 to 60 atm and 150-200°C. Carbon monoxide can combine with higher alcohols, however, at a much slower reaction rate. 

A nucleophilic addition to the triple bond in alkynylphosphine derivatives was observed by Laguna and Bardaji and although there was no evidence for a gold catalyzed cycle, reaction conditions were extremely milder than in the classic Reppe vinylation [94] (Scheme 8.12). 

Propionic Acid. The Reppe reaction is used to transform ethylene, carbon monoxide, and water to propionic acid.82 [Ni(CO)4] is formed in situ from nickel salts under reaction conditions (270-320°C, 200-240 atm). The addition of halogens and phosphine ligands allows milder reaction conditions (Halcon process, 170-225°C, 10-35 atm). Propionic acid yields are around 95%. 

The industrial catalytic Reppe process is usually applied in the production of acrylic acid. The catalyst is NiBr2 promoted by copper halides used under forcing conditions. The BASF process, for example, is operated at 225°C and 100 atm in tetrahydrofuran solvent.188 Careful control of reaction conditions is required to avoid the formation of propionic acid, the main byproduct, which is difficult to separate. Small amounts of acetaldehyde are also formed. Acrylates can be produced by the stoichiometric process [Eq. (7.20)], which is run under milder conditions (30-50°C, 1-7 atm). The byproduct NiCl2 is recycled ... 

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]. 

The applied nickel catalyst, promoted by copper halides, required rather severe reaction conditions T = 220 °C, F = 10 MPa), but gave good AA yields up to 90% based on acetylene. This so-called catalytic Reppe process was commercially operated in Germany, the USA, and Japan. Due to the limited availability of cheap acetylene as feedstock and the severe reaction conditions involved in the carbonylation process, this process has lost the competition with (heterogeneously catalyzed) oxidation of readily available propene, even though a perfect selectivity to AA is not achieved in the latter process. 

Thermal cyclooligomerizations of olefins and alkynes require severe and often dangerous reaction conditions and the yields of cyclic products are usually very low. Acetylene ean be trimerized to benzene at 500 °C [1] and butadiene (BD) dimerizes at 270 °C and under high pressure to give small amounts of 1,5-cyclo-octadiene [2]. Reppe s discovery in 1940 that acetylene can be cyclotetramerized to cyclooctatetraene (COT) using a nickel catalyst [3] shows that transition metals can act as templates for the synthesis of cyclic hydrocarbons from acetylenic or olefinic building blocks (Scheme 1). 

Monomer Synthesis. The synthesis of 1 was based on the published procedure of Reppe for the divinyl ether of triethylene glycol (11) The reaction conditions given in the Experimental were those found to give the best yields of 1 with this method. Some variations in reaction time and temperature as well as catalyst concentration were examined in attempts to improve the yield. Milder conditions reduced the rate of reaction without increasing the final yield, while harsher conditions led to extensive decomposition. Several additional mono- and divinyl ethers of oligo-oxyethylenes have been synthesized with this procedure and in general, yields were low. 

In the same way as in Reppe chemistry the reaction conditions could be mitigated by including organic bases in the catalysts, more and more organic molecules will be added as ligands to central metal atoms. Thus catalysts will be built up according to the pattern of such biocatalysts as chlorophyll and porphyrine which are effective even at mild conditions. 

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. ... 

The representative carbonylations with rhodium catalysts is the Monsanto acetic acid process which started in 1970 with a production amount of three million pounds per year [82-91]. In this carbonylation, the 0x0 process of the Reppe reaction is carried out at 250-270°C, 200-300atm with nickel catalysts, and the BASF process is carried out at 210°C, 530atm with a Co/I catalyst. However, the Monsanto acetic acid process shown in eq. (18.37) is carried out under mild reaction conditions in a high selectivity of acetic acid with rhodium catalyst. The catalyst is RhCl3 3H20 and the active species is considered to be [Rh(CO)2l2] ... 

A number of cyclic carbonyl compounds are formed under the conditions of the Reppe reaction or of the Koch acid synthesis. Since the reactions are carried out in the presence of water they can either proceed via... 

Another example is the carbonylation of allyl carbinol under the conditions of the Reppe reaction [525], yielding a-methyl-y-butyrolactone plus S-valerolactone. 

Reaction of coke with calcium oxide gives calcium carbide, which on treatment with water produces acetylene. This was for many years an important starting point for the production of acrylonitrile, vinyl chloride, vinyl acetate and other vinyl monomers. Furthermore, during World War II, Reppe developed routes for many other monomers although these were not viable under normal economic conditions. 

REPPE PROCESS. Any of several processes involving reaction of acetylene (1) with formaldehyde to produce 2-butync-l,4-diol which can be converted to butadiene (2) with formaldehyde under different conditions to produce propargyl alcohol and, form this, allyl alcohol (3) with hydrogen cyanide to yield acrylonitrile (4) with alcohols to give vinyl ethers (5) with amines or phenols to give vinyl derivatives (6) with carbon monoxide and alcohols to give esters of acrylic acid (7) by polymerization to produce cyclooctatetraene and (8) with phenols to make resins. The use of catalysis, pressures up to 30 atm, and special techniques to avoid or contain explosions are important factors in these processes. 

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). 

An initial finding was the catalytic activity of Cul under solvent-free conditions in which an acceleration by microwave irradiation was reported (Scheme 12.1).8 The reaction probably proceeds through an iminium or imine species thus there is a close relationship to the historic work of Reppe for the formation of the corresponding propargyl alcohols. 

Even if new processes of synthesis were developed from alcohols, like catalytic vinylation with ethylene or vinyl exchange with vinyl acetate, the major commercial route for VE monomers seams to be still the Reppe method based on reaction, in basic conditions, of acetylene with the corresponding alcohols [96,97,100] ... 

In Reppe chemist ty, the metal-hydrogen bond is often obtained by the conversion of one mole of carbon monoxide to carbon dioxide by reaction with water, a reaction which is favoured by alkaline conditions... 

The acid-catalyzed hydrocarboxylation of alkenes (the Koch reaction) can be performed in a number of ways. In one method, the alkene is treated with carbon monoxide and water at 100-350°C and 500-1000-atm pressure with a mineral acid catalyst. However, the reaction can also be performed under milder conditions. If the alkene is first treated with CO and catalyst and then water added, the reaction can be accomplished at 0-50°C and 1-100 atm. If formic acid is used as the source of both the CO and the water, the reaction can be carried out at room temperature and atmospheric pressure.The formic acid procedure is called the Koch-Haaf reaction (the Koch-Haaf reaction can also be applied to alcohols, see 10-77). Nearly all alkenes can be hydrocarboxylated by one or more of these procedures. However, conjugated dienes are polymerized instead. Hydrocarboxylation can also be accomplished under mild conditions (160°C and 50 atm) by the use of nickel carbonyl as catalyst. Acid catalysts are used along with the nickel carbonyl, but basic catalysts can also be employed. Other metallic salts and complexes can be used, sometimes with variations in the reaction procedure, including palladium, platinum, and rhodium catalysts. The Ni(CO)4-catalyzed oxidative carbonylation with CO and water as a nucleophile is often called Reppe carbonylationP The toxic nature of nickel... 

In recent years, attention has been focused on alkyne carbonylation catalysts based on the metals nickel, palladium, and platinum, modified with a variety of tertiary (bi)phosphines [5]. TTie main goal has been to develop chemo- and regio-selective carbonylation catalysts for application to higher alkyne substrates for the synthesis of certain fine chemicals. Many of these catalysts do allow the carbonylation to proceed under milder conditions than those applied in the catalytic Reppe process, and some of these catalysts do provide the branched regioisomer product from higher alkynes with good selectivity. However, in all cases reaction rates are very low, i.e., below 100 (and in most cases even below 10) mol/mol metal per h, as are the product yields in mol/mol metal (< 100). These catalyst productivities are far too low for large-scale industrial application in the production of commodity-type products, such as (meth)acrylates. 

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 ... 

With Hugo Kroper, he demonstrated that carbon monoxide and ethylene formed propionic acid at 300°C and 200 atmospheres under the influence of nickel carbonyl. A silver-lined pilot plant for a continuous process was erected in 1943, but, owing to the war and the French occupation, a semi-works plant was not ready until 1951. Even before the outbreak of war in 1939, Reppe had used nickel carbonyl to carbonylate methanol to acetic acid, a reaction previously only possible under extreme conditions of pressure and temperature. The war (and corrosion problems) delayed its development for over a decade and a full-scale plant was not built until 1957. It is still used at Ludwigshafen and by Borden at Geismar, Louisiana. ... 

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