Carbonylation propionic acid

The Stobbe condensation thus provides a method for introducing a propionic acid residue at the site of a carbonyl group. 

Propionic acid is accessible through the Hquid-phase carbonylation of ethylene over a nickel carbonyl catalyst (104), or via ethylene and formic acid over an iridium catalyst (105). Condensation of propionic acid with formaldehyde over a supported cesium catalyst gives MAA directiy with conversions of 30—40% and selectivities of 80—90% (106,107). Catalyst lifetime can be extended by adding low levels (several ppm) of cesium to the feed stream (108). 

The advent of a large international trade in methanol as a chemical feedstock has prompted additional purchase specifications, depending on the end user. Chlorides, which would be potential contaminants from seawater during ocean transport, are common downstream catalyst poisons likely to be excluded. Limitations on iron and sulfur can similarly be expected. Some users are sensitive to specific by-products for a variety of reasons. Eor example, alkaline compounds neutralize MTBE catalysts, and ethanol causes objectionable propionic acid formation in the carbonylation of methanol to acetic acid. Very high purity methanol is available from reagent vendors for small-scale electronic and pharmaceutical appHcations. 

An isoindol1 none moiety forms part of the aromatic moiety of yet another antiinflammatory propionic acid derivative. Carboxylation of the anion from -nitro-ethylbenzene (45) leads directly to the propionic acid (46). Reduction of the nitro group followed by condensation of the resulting aniline (47) with phthalic anhydride affords the corresponding phthalimide (48). Treatment of that intermediate with zinc in acetic acid interestingly results in reduction of only one of the carbonyl groups to afford the isoindolone. There is thus obtained indoprofen (49). ... 

Johnson s classic synthesis of progesterone (1) commences with the reaction of 2-methacrolein (22) with the Grignard reagent derived from l-bromo-3-pentyne to give ally lie alcohol 20 (see Scheme 3a). It is inconsequential that 20 is produced in racemic form because treatment of 20 with triethyl orthoacetate and a catalytic amount of propionic acid at 138 °C furnishes 18 in an overall yield of 55 % through a process that sacrifices the stereogenic center created in the carbonyl addition reaction. In the presence of propionic acid, allylic alcohol 20 and triethyl orthoacetate combine to give... 

Addition of the dianion of /5-sulphinylcarboxylic acids to carbonyl compounds leads to the formation of the corresponding hydroxy derivatives which undergo spontaneous cyclization to give y-lactones440. Bravo and coworkers have found that when optically active ( + )-(R)-3-(p-toluenesulphinyl)propionic acid 426 is used for this reaction, the corresponding diastereoisomeric / -sulphinyl-y-lactones 427 are formed in a ratio which is dependent on the substituents in the carbonyl component441,502 503 (equation 256). 

Similar aggressive reaction conditions characterize the hydrolysis of acid chlorides, in particular when using short-chain alkyl-substituted acid chlorides such as propionic acid chloride. This fast reaction serves well as a model reaction for micro channel processing, especially for IR monitoring owing to the strong changes in the carbonyl peak absorption by reaction [21]. 

Rhodium catalyzed carbonylations of olefins and methanol can be operated in the absence of an alkyl iodide or hydrogen iodide if the carbonylation is operated in the presence of iodide-based ionic liquids. In this chapter, we will describe the historical development of these non-alkyl halide containing processes beginning with the carbonylation of ethylene to propionic acid in which the omission of alkyl hahde led to an improvement in the selectivity. We will further describe extension of the nonalkyl halide based carbonylation to the carbonylation of MeOH (producing acetic acid) in both a batch and continuous mode of operation. In the continuous mode, the best ionic liquids for carbonylation of MeOH were based on pyridinium and polyalkylated pyridinium iodide derivatives. Removing the highly toxic alkyl halide represents safer, potentially lower cost, process with less complex product purification. 

Recently, Eastman Chemical Company reported that ionic liquids can be successfully employed in a vapor take-off process for the carbonylation of methanol to acetic acid in the presence of rhodium and methyl iodide (3). While attempting to extend this earlier work to the carbonylation of ethylene to propionic acid, we discovered that, when using ionic liquids as a solvent, acceptable carbonylation rates could be attained in the absence of any added alkyl iodide or hydrogen iodide (4). We subsequently demonstrated that the carbonylation of methanol to acetic acid could also be operated in the absence of methyl iodide when using ionic liquids (5). 

In this manuscript, we will chronicle the discoveiy and development of these non-alkyl halide containing processes for the rhodium catalyzed carbonylation of ethylene to propionic acid and methanol to acetic acid when using ionic liquids as solvent. 

Ethylene Carbonylation. The classical rhodium catalyzed carbonylation of ethylene to propionic acid (Eqn. 1) used ethyl iodide or HI as a co-catalyst (6). In the presence of excess ethylene and CO the process could proceed further to propionic anhydride (Eqn. 2). While additional products, such as ethyl propionate (EtC02Et), diethyl ketone (DEK), and ethanol were possible (See Eqns. 3-5), the only byproduct obtained when using a rhodium-alkyl iodide catalyst was small amounts (ca. 1-1.5%) of ethyl propionate. (See Eqns. 3-5.)... 

It appeared that, we needed to limit or omit the ethyl iodide if we were going to operate the ethylene carbonylation in ionic liquids. Unfortunately, the previous literature indicated that EtI or HI (which are interconvertible) represented a critical catalyst component. Therefore, it was surprising when we found that, in iodide based ionic liquids, the Rh catalyzed carbonylation of ethylene to propionic acid was still operable at acceptable rates in the absence of ethyl iodide, as shown in Table 37.2. Further, we not only achieved acceptable rates when omitting the ethyl iodide, we also achieved the desired reduction in the levels of ethyl propionate. More importantly, when the reaction products were analyzed, there was no detectable ethyl iodide formed in situ. However, we should note that we now observed traces of ethanol which were normally undetectable in the earlier Ed containing experiments. 

Subsequent insertion of CO into the newly formed alkyl-ruthenium moiety, C, to form Ru-acyl, D, is in agreement with our 13C tracer studies (e.g., Table III, eq. 3), while reductive elimination of propionyl iodide from D, accompanied by immediate hydrolysis of the acyl iodide (3,14) to propionic acid product, would complete the catalytic cycle and regenerate the original ruthenium carbonyl complex. 

Procedures for the preparation of several compounds of considerable utility are described. These include 1,1 -carbonyl-diimidazole, which has been used in the preparation of esters, amides, and anhydrides, the hydrochloride and methiodide of l-ethyl-3-(3-dimethylamino)-propylcarbodiimide, which can be used for similar purposes and are especially useful in the preparation of peptides, and (+)- and (— )-< -(2,4,5,7-tetranitro-9-fluorenylideneaminooxy) propionic acid (TAPA), which is used for the resolution of polycyclic aromatic compounds. 

In chlorophyll iron as complex-forming metal is replaced by magnesium (Willstatter). The structure of chlorophyll differs from that of haemin as follows. In chlorophyll one propionic acid chain (a) in oxidised form has condensed with a methine carbon atom to form a cyclopentane ring which takes the position at (c) of the vinyl ethyl. Further the two carbonyl groups are esterified and one of the four pyrrole rings is partially hydrogenated... 

A typical configuration for a methanol carbonylation plant is shown in Fig. 1. The feedstocks (MeOH and CO) are fed to the reactor vessel on a continuous basis. In the initial product separation step, the reaction mixture is passed from the reactor into a flash-tank where the pressure is reduced to induce vapourisation of most of the volatiles. The catalyst remains dissolved in the liquid phase and is recycled back to the reactor vessel. The vapour from the flash-tank is directed into a distillation train which removes methyl iodide, water and heavier by-products (e.g. propionic acid) from the acetic acid product. 

Carbonylation of IBPE and other 2-arylethanols with various organosoluble Pd-catalysts was studied in detail with special emphasis on the role of the promoters p-toluenesulfonic acid and LiCl [55], Some of the catalytic species, such as [PdCl(PPh3)2] formed from [Pd(PPh3)4] or from Pd(II) precursors in aqueous methylethylketone (MEK) under reaction conditions (54 bar CO, 105 °C) were identified by P NMR spectroscopy. Ibuprofen was obtained in a fast reaction (TOP = 850 h" ) with 96% yield (3-IPPA 3.9 %), while the carbonylation of l-(6-methoxynaphtyl)ethanol gave 2-(6-methoxynaphtyl)propionic acid (Naproxen) with high selectivity (97.2 %) but with moderate reaction rates (TOP = 215 h" ). 

Later Gronowitz and Maltesson reported the extension of this method to the preparation of thieno[2,3-6]thiophene (1) derivatives. A mixture of 3-(3-thienyl)acrylic acid, thionyl chloride, and pyridine was heated for 24 hours. 2-Chloro-3-(3-thienyl)-acrylic acid (4.5%), 3,5-dichlorothieno[2,3-6]thiophene-2-carbonyl chloride (99) (9.5%), 3-chlorothieno[2,3-Z)]thiophene-2-carbonyl chloride (100) (79.1%), and other compounds were detected by GLC among the reaction products [Eq. (31)]. Hydrolysis of the reaction mixture gave 3-chlorothieno[2,3-Z>]thiophene-2-carboxylic acid in 63% yield dechlorination of the latter by copper in propionic acid converted it into thieno[2,3-6]thiophene-2-carboxylic acid. 

Reactions lla-e add up to Reaction 10. Reactions lla-b have been shown above to be catalyzed by Rh/CH3l. Reaction 11c, i.e. acid-catalysed pyrolysis of EDA to acetaldehyde and acetic anhydride, is well documented (9). Both reaction lid, hydrogenation of aldehyde, and Reaction lie, carbonylation of alcohols, are of course well known. The reaction sequence is in agreement with the fact that EDA and AH, especially in short-duration experiments, are detected as by-products. Acetaldehyde is also observed in small quantities, but no ethanol is found. Possibly, Reactions lid and He occur concertedly. We have separately demonstrated that both EDA and AH are suitable feeds to produce propionic acid under homologation reactions conditions. We thus demonstrated... 

Ibuprofen (+) -2- (4-Isobutylphenyl) propionic acid Aromatic alkylation, HF-catalyzed aromatic acetylation, palladium-catlayzed carbonylation, alkene hydration... 

An early effort to generate a 3-lithiated propionic acid derivative and react it with (external) electrophiles was reported in 1978 [42]. Since simple 3-lithioesters failed to undergo the required reaction, the alkyl carboxylate portion was protected by preceding conversion to the carboxylate anion. Treatment of lithium 3-bromo-propionate with lithium naphthalide generated the desired dilithiated propionic acid, which gave moderate yields of y-hydroxy acid addition products with carbonyl compounds, Eq. (45). 

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). 

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