Reppe reactions

Acetylene-Based Routes. Walter Reppe, the father of modem acetylene chemistry, discovered the reaction of nickel carbonyl with acetylene and water or alcohols to give acryUc acid or esters (75,76). This discovery led to several processes which have been in commercial use. The original Reppe reaction requires a stoichiometric ratio of nickel carbonyl to acetylene. The Rohm and Haas modified or semicatalytic process provides 60—80% of the carbon monoxide from a separate carbon monoxide feed and the remainder from nickel carbonyl (77—78). The reactions for the synthesis of ethyl acrylate are... 

Monosubstituted acetylenes add formaldehyde in the presence of copper, silver, and mercury acetyUde catalysts to give acetylenic alcohols (58) (Reppe reaction). Acetylene itself adds two molecules (see Acetylene-DERIVED chemicals). 

Acrylic Acid. In Europe some acryHc acid [79-10-7] and ester is manufactured by the Reppe reaction from acetjdene, methanol, and carbon monoxide (eq. 10) (see Aacrylic acid and derivatives). 

In hydrocarboxylation, the Reppe reaction, the catalyst can be nickel or cobalt carbonyl or a palladium complex where R = H or alkyl. 

Having greater resemblance to natural fatty acids are the products of the coordination-catalyzed hydrocarboxylation of olefins with water and carbon monoxide (Reppe reaction) [58] ... 

In the metal-carbonyl catalysed hydrocarboxylation of alkynes ( Reppe reaction ) nearly exclusive cia-addition of H—COOH is found (Ohashi et al., 1952). 

We are interested in homogeneous catalytic methanol synthesis because of our previous work on the Reppe reactions (11,12,13)2... 

Scheme 9.7. Proposed reaction course for the metalative Reppe reaction.

Uses Artificial resins perfumery solvent adhesives protective coatings special fuel organic synthesis (Grignard and Reppe reactions). 

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. Mullen, Carbonylation Catalyzed by Metal Carbonyls-Reppe-Reactions, in J. Falbe, New Synthesis... 

The syntheses of carboxylic acids and esters are widely studied processes. Since the first examples of carboxylation in the presence of metal carbonyls were reported by Reppe, these reactions are sometimes referred to as the Reppe reactions. In his pioneering work125-127 stoichiometric or catalytic amounts of [Ni(CO)4] and ethylene or acetylene were reacted in the presence of water or alcohols to form saturated and unsaturated acids and esters. Commercial processes are practiced in the manufacture of propionic acid, acrylic acid and acrylates (see Section 7.2.4). 

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%. 

Acrylic Acid and Acrylates. Acrylic acid and acrylates may be produced commercially by the Reppe reaction of acetylene.76,184-187 However, the industrial significance of these processes has diminished since acetylene is no longer a viable source and was replaced by ethylene. Acrylic acid and acrylates are now produced by propylene oxidation (see Section 9.5.2). 

Reppe reaction - [FORMALDEHYDE] (Vol 11) -C-19 dicarboxylic acids from [DICARBOXYLIC ACIDS] (Vol 8)... 

Hydroesterification is one of the Reppe reactions in which carbon monoxide, an alcohol, and an alkene react to esters (Scheme 21). This reaction is also called alkoxycarbonylation, hydroalkoxycarbonylation, and hydrocarbalkoxylation. 

Figure 22-8 Some carbonylation reactions. Reppe reactions involve CO + H20 or CO + ROH. Koch reactions involve CO + H20 in strongly acidic solution. Oxidative carbonylations may involve 02, NO, or ROOR.

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 ... 

The reaction of an aUcene (or aUcyne), CO, and H2O to directly produce a carboxylic acid is called Reppe carbony-lation chemistry or, more recently, hydrocarboxylation (see Reppe Reaction). An excellent review of palladium-catalyzed Reppe carbonylation systems has been published recently by Kiss, and coverage of this important material will not be repeated here. This catalytic reaction has been known for quite some time, although the stoichiometric Ni(CO)4-based carbonylation of acetylene was the first commercial carbonylation process implemented (equation 13). The extreme toxicity of Ni(CO)4, however, has limited practical applications (see Nickel Organometallic Chemistry). Co, Rh, and Pd catalysts have certainly replaced Ni(CO)4 in smaller-scale laboratory reactions, though for historical reasons a number of the fim-damental mechanisms discussed in this section are based on Ni(CO)4. 

Metallacycles have been claimed to play pivotal roles in many transition metal-mediated multi-component coupling reactions [1]. For example, [2 -i- 2 -i- 2] alkyne cyclo-trimerization leading to benzenes - the Reppe reaction - has been considered to proceed via metallacyclopentadiene and elusive metallacycloheptatriene intermediates ("common mechanism ), while metallacyclopentenes have been proposed as intermediates for the [2 -i- 2 -i- 1] cyclo-coupling reactions of an alkyne, an alkene, and CO leading to a cyclopentenone (the Pauson-Khand reaction). A metallacyclic compound - which is defined here as a carbocyclic system with one atom replaced by a transition metal element - can be generally formed by oxidative cyclization of two unsaturated molecules with a low-valent transition metal fragment [2-4]. Alter-... 

Subsequent protic workup releases the aromatic compound. The metalative Reppe reaction can also be used to prepare iodo-substituted or homologated aromatics by treatment of the titanium aryl compound with iodine or an aldehyde, respectively. This procedure has recently been extended to include pyridine derivatives (254 and 255), where the titanacyclopentadiene intermediate can be treated with sulfonylnitriles to afford pyridines after protic workup.192 As with the alkyne cyclotrimerizations, treatment with the appropriate electrophiles affords iodo- and homologated pyridines. 

Compared with the Diels-Alder reaction, the [2+2+2]-cycloaddition is potentially more powerful since the number of new bonds as well as chirality centers that are formed is higher. Unfortunately, the reaction seems to be entropically or kinetically unfavorable. This disadvantage can, however, be overcome by the use of transition metal catalysts (templates). Among the most successful examples of this reaction type, the nickel(II) catalyzed Reppe reactions 96), the cobalt(I) catalyzed cocyclizations of a,to-diynes with alkynes 97), the cobalt(I) catalyzed pyridine synthesis 985 and last but not least the palladium(0) catalyzed cyclotrimerizations of 3,3-dialkylcyclopropenes to frans-cr-tris-homobenzenes must be mentioned. The latter has been known for ten years 99>. 

The only industrial application, the synthesis of butanol from propene (Reppe synthesis), was not very successful (297). This reaction is catalyzed by iron carbonyls in the presence of tertiary ammonium salts the trinu-clear cluster anion [HFe3(CO) ] detected in the reaction mixture has been discussed as the active species (298). Spectroscopic studies under CO pressure, however, showed the trinuclear anion [HFe3(CO) ]- to be converted into the mononuclear species [HFe(CO)4] (299), and this anion is now assumed to be the catalyst in the Reppe reaction (290). 

In Reppe reaction with water gas shift catalyst 14.6.6.2.2 Insertion reactions of 14.1.2.6. Oligomerization of ... 

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