Acetic propionic acid synthesis

With the exception of acetic, acryUc, and benzoic all other acids in Table 1 are primarily produced using oxo chemistry (see Oxo process). Propionic acid is made by the Hquid-phase oxidation of propionaldehyde, which in turn is made by appHcation of the oxo synthesis to ethylene. Propionic acid can also be made by oxidation of propane or by hydrocarboxylation of ethylene with CO and presence of a rhodium (2) or iridium (3) catalyst. 

The tetramerization of suitable monopyrroles is one of the simplest and most effective approaches to prepare porphyrins (see Section 1.1.1.1.). This approach, which is best carried out with a-(hydroxymethyl)- or ot-(aminomethyl)pyrroles, can be designated as a biomimetic synthesis because nature also uses the x-(aminomethyl)pyrrole porphobilinogen to produce uroporphyrinogen III. the key intermediate in the biosynthesis of all kinds of naturally occurring porphyrins, hydroporphyrins and corrins. The only restriction of this tetramerization method is the fact that tnonopyrroles with different -substituents form a mixture of four constitutionally isomeric porphyrins named as porphyrins I, II, III, and IV. In the porphyrin biosynthesis starting from porphobilinogen, which has an acetic acid and a propionic acid side chain in the y6-positions, this tetramerization is enzymatically controlled so that only the type III constitutional isomer is formed. 

Tocopheryl)propionic acid (50) is one of the rare examples that the o-QM 3 is involved in a direct synthesis rather than as a nonintentionally used intermediate or byproduct. ZnCl2-catalyzed, inverse hetero-Diels-Alder reaction between ortho-qui-none methide 3 and an excess of <2-methyl-C,<9-bis-(trimethylsilyl)ketene acetal provided the acid in fair yields (Fig. 6.37).67 The o-QM 3 was prepared in situ by thermal degradation of 5a-bromo-a-tocopherol (46). The primary cyclization product, an ortho-ester derivative, was not isolated, but immediately hydrolyzed to methyl 3-(5-tocopheryl)-2-trimethylsilyl-propionate, subsequently desilylated, and finally hydrolyzed into 50. 

FIGURE 6.37 Synthesis of 3-(5-tocopheryl)-propionic acid (50) by trapping the intermediate ortho-QM 3 with a ketene acetal. Reaction products of 50 are formed in complete analogy to a-tocopherol (1). 

The reaction of potassium 3-amino-4-oxo-3,4-dihydroquinazoline-2-thiolate 62 with a-bromophenylacetic acid 63 resulted in the formation of (3-amino-4-oxo-3,4-dihydroquinazolin-2-ylsulfanyl)-phenyl-acetic acid methyl ester 64 which on alkali treatment and subsequent acidification resulted in the synthesis of 2-phenyl- 1-thia-4,4a,9-triaza-anthracene-3,10-dione 65 <1999JCR(S)86>. Similarly, the reaction of potassium 3-amino-5,6-dimethyl-4-oxo-3,4,4a,7a-tetrahydrothieno[2,3- pyrimidine-2-thiolate 66 with a-bromo-ester 67 resulted in the formation of 2-(3-amino-5,6-dimethyl-4-oxo-3,4,4a,7a-tetrahydrothieno[2,3- / pyrimidin-2-ylsulfanyl)-propionic acid ethyl ester 68. Subsequent treatment with alkali followed by acidification resulted in the formation of 2,3,7-trimethyl-3a,9a-dihydro-l,8-dithia-4a,5,9-triazacyclopenta[ ]naphthalene-4,6-dione 69 <2000JHC1161>... 

Aryl-acetic or -propionic acids as well as benzylketones are versatile intermediates for the synthesis of pharmaceuticals, agrochemicals, or fragrances. Many methods have already been explored, notably using electrochemistry and transition metal compounds. 

Production of Ethyl Acetate and Propionic Acid from Methanol and Synthesis Gas... 

It will be shown that Reactions 2 and 3 can be made to proceed at a high rate and with a high selectivity. Combined with simple esterification. Reactions 2 and 3 form a basis for two-step routes for the synthesis of respectively ethyl acetate and propionic acid starting from methanol and synthesis gas as the only feedstock. 

The homolytic substitution of thiophene by electrophilic carbon radicals provides a good method for the synthesis of (2-thienyl)acetic and (2-thienyl)propionic acids. The electrophilic radical, CH2C02Et, generated from ICH2C02Et, H202 and catalytic Fe2+ in DMSO, reacts with thiophene to form (2-thienyl)acetic ester in 62% yield (92JOC6817). 

Biotin enzymes are believed to function primarily in reversible carboxvlahon-decarboxylation reactions. For example, a biotin enzyme mediates the carboxylation of propionic acid to methylmalonic add, which is subsequently converted to succinic acid, a dtric acid cycle intermediate. A vitamin Bl2 coenzyme and coenzyme A are also essential to this overall reaction, again pointing out the interdependence of the B vitamin coenzymes. Another biotin enzyme-mediated reaction is the formation of malonyl-CoA by carboxylation of acetyl-CoA ( active acetate ). Malonyl-CoA is believed lo be a key intermediate in fatly add synthesis. 

Cellulose esters of the 2-.. 3-. and 4-carbon acids are readily prepared by the cellulose-anhydride reaction the acetate ester and the mixed acetate butyrate and acetate propionate esters arc manufactured and used in large amounts. Esters of higher acids require different synthesis techniques and tend to be prohibitively expensive except as specialty products. Some arc in commercial production, however. Cellulose acclalc phlhalatc, for example, is manufactured for use as an enteric coating on pills. 

Butane from natural gas is cheap and abundant in the United States, where it is used as an important feedstock for the synthesis of acetic acid. Since acetic acid is the most stable oxidation product from butane, the transformation is carried out at high butane conversions. In the industrial processes (Celanese, Hills), butane is oxidized by air in an acetic acid solution containing a cobalt catalyst (stearate, naphthenate) at 180-190 °C and 50-70 atm.361,557 The AcOH yield is about 40-45% for ca. 30% butane conversion. By-products include C02 and formic, propionic and succinic acids, which are vaporized. The other by-products are recycled for acetic acid synthesis. Light naphthas can be used instead of butane as acetic adic feedstock, and are oxidized under similar conditions in Europe where natural gas is less abundant (Distillers and BP processes). Acetic acid can also be obtained with much higher selectivity (95-97%) from the oxidation of acetaldehyde by air at 60 °C and atmospheric pressure in an acetic acid solution and in the presence of cobalt acetate.361,558... 

The reaction of nitroarenes with silyl end ethers and ketene silyl acetals in MeCNATiF with 1 equiv. of TASF, followed by in situ oxidation with Br2 or DDQ, provides an easy route to a-nitroaryl carbonyl compounds (Scheme l).12 The use of these compounds as reagents for the synthesis of arylacetic acids, propionic acids, indoles, 2-indolinones and other heterocyclic compounds has recently been described.88... 

The use of extracellular lipases of microbial origin to catalyze the stereoselective hydrolysis of esters of 3-acylthio-2-methylpropionic acid in an aqueous system has been demonstrated to produce optically active 3-acylthio-2-methyl-propionic acid [41-43], The synthesis of the chiral side chain of captopril by the lipase-catalyzed enantioselective hydrolysis of the thioester bond of racemic 3-acetylthio-2-methylpropionic acid (15) to yield 5 -(-)-(15) has been demonstrated [44], Among various lipases evaluated, lipase from Rhizopus oryzae ATCC 24563 (heat-dried cells), BMS lipase (extracellular lipase derived from the fermentation of Pseudomonas sp. SC 13856), and lipase PS-30 from Pseudomonas cepacia in an organic solvent system (l,l,2-trichloro-l,2,2-tri-fluoroethane or toluene) catalyzed the hydrolysis of thioester bond of undesired enantiomer of racemic (15) to yield desired S-(-) (15), R-(+)-3-mercapto-2-methylpropionic acid (16) and acetic acid (17) (Fig. 8A). The reaction yield of... 

The de novo synthesis of fatty acids in the mammary gland utilizes mainly acetate and some (3-hydroxybutyrate. These precursors arise from the microbial fermentation of cellulose and related materials in the rumen. Once in the mammary gland, acetate is activated to acetyl-CoA. The mechanism of fatty acid synthesis essentially involves the carboxylation of acetyl-CoA to malonyl-CoA, which is then used in a step-wise chain elongation process. This leads to a series of short-chain and medium-chain length fatty acids, which differ by two CH2 groups (e.g., 4 0, 6 0, 8 0, etc.) (Hawke and Taylor, 1995). These are straight-chain, even-numbered carbon fatty acids. However, if a precursor such as propionate, valerate or isobutyrate, rather than acetate, is used, branched-chain or odd-numbered carbon fatty acids are synthesised (Jenkins, 1993 see Chapter 2). 

The synthesis of diazonium salts of less basic amines does not proceed satisfactorily under the above conditions because of the reduced nucleophilic nature of the amino group and the reaction is usually carried out in concentrated sulfuric acid. The addition of sodium nitrite to concentrated sulfuric acid produces the stable nitrosylsulfuric acid, (NOHSO ). Diazotization of the most weakly basic amines is carried out using nitrosylsulfuric acid in a mixture of one part of propionic acid in five parts of acetic acid at 0-5 °C. The propionic acid prevents the mixture from freezing. 

Polyketide and fatty acid biosyntheses begin with condensation of the coenzyme A thioester of a short-chain carboxylic acid starter unit such as acetate or propionate with the coenzyme A thioester of a dicarboxylic acid extender unit such as malonate or methyl malonate. The driving force for the condensation is provided by the decarboxylation of the extender unit. In the case of fetty acid synthesis, the resulting -carbonyl is completely reduced to a methylene however, during the synthesis of complex poly-ketides, the -carbonyl may be left untouched or variably reduced to alcohol, olefinic, or methylene functionalities depending on the position that the extender unit will occupy in the final product. This cycle is repeated, and the number of elongation cycles is a characteristic of the enzyme catalyst. In polyketide biosynthesis, the full-length polyketide chain cyclizes in a specific manner, and is tailored by the action of additional enzymes in the pathway. 

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