Aceto groups

Ritchey et al. (113) showed the introduction of trifluoroacetate groups at the unsubstituted hydroxyls of cellulose acetate causes a reversal in handedness of the cholesteric structure. Likewise the introduction of an aceto group in acetox3rpropyl cellulose changes the twist (116). 

Reduction of a multisubstituted aromatic compound is functional group selective, where selectivity is based on the reduction potentials. For example, the aldehyde group is reduced in p-cyanobenzaldehyde and p-acetobenzal-dehyde, whereas cyano and aceto groups are not. The nitro group, however, is reduced more readily than the aldehyde group when p-nitrobenzaldehyde is employed as a substrate [23]. The reduction efficiency for an aliphatic aldehyde is much less than that for an aromatic one because of the difference in reduction potentials. 

An alternative common name for 3-oxobutanoic acid is acetoacetic acid. In deriving this common name, this ketoacid is regarded as a substituted acetic acid, and the CH3C(=O) — substituent is named an aceto group. 

Aceto group (Section 17.2B) A CH3CO— group also called an acetyl group. 

It follows therefore that ethyl malonate can be used (just as ethyl aceto- acetate) to prepare any mono or di-substituted acetic acid the limitations are identical, namely the substituents must necessarily be alkyl groups (or aryl-alkyl groups such as CjHjCHj), and tri-substituted acetic acids cannot be prepared. Ethyl malonate undergoes no reaction equivalent to the ketonic hydrolysis of ethyl acetoacetate, and the concentration of the alkali used for the hydrolysis is therefore not important. 

An unactivated methyl group can be functionalized by the cyclopalladation of oximes. The equatorial methyl of geminal methyls in steroids or hexapyr-anosides is selectively aceto.xylated by the reaction of the palladation complex 523 of the 3-oxime with lead tetraacetate[467,468]. 

Acetoiicetyliition Reactions. The best known and commercially most important reaction of diketene is the aceto acetylation of nucleophiles to give derivatives of acetoacetic acid (Fig. 2) (1,5,6). A wide variety of substances with acidic hydrogens can be acetoacetylated. This includes alcohols, amines, phenols, thiols, carboxyHc acids, amides, ureas, thioureas, urethanes, and sulfonamides. Where more than one functional group is present, ring closure often follows aceto acetylation, giving access to a variety of heterocycHc compounds. These reactions often require catalysts in the form of tertiary amines, acids, and mercury salts. Acetoacetate esters and acetoacetamides are the most important industrial intermediates prepared from diketene. 

Production of poly(3HB-co-3HV) co-polymer in plants has recently been demonstrated by the PHA group of Monsanto [27], which acquired the PHA business of Zeneca in 1996. In the commercial production of poly(3HB-co-3HV) from R. eutropha, propionate is added to the growth media in order to create an intracellular pool of propionyl-CoA which can be condensed to acetyl-CoA to form 3-ketovaleryl-CoA. The 3-ketovaleryl-CoA is then reduced by the aceto-acetyl-CoA reductase to give 3-hydroxyvaleryl-CoA, which is co-polymerized with 3-hydroxybutyryl-CoA to synthesize poly(3HB-co-3HV) (Fig. 1). For the synthesis of poly(3HB-co-3HV) in plants, it was thus necessary to create an endogenous pool of propionyl-CoA which could be used by the PHA pathway. 

Aliquat is an efficient catalyst for the acetoacetylation of amines by diketene. The initially formed amides react with an excess of the diketene to form, after cyclization of the secondary product, 1-substituted 3-acetyl-4-hydroxy-6-methylpyrid-2-ones [39]. Amides react under similar conditions with diketene to form A-acyl aceto-acetamides, which react further with a second molecule of diketene to yield, after cleavage of the A-acyl group, 3-acetyl-4-hydroxy-6-methylpyrid-2-one [39]. 

Hayashi and his co-workers investigated the reactions of 2-substituted quinoxaline 4-oxides with ketones.210-212 2-Phenylquinoxaline 4-oxide (193) yields 2-phenyl-3-phenacylquinoxaline 4-oxide (203) with acetophenone and sodamide. However, 2-cyanoquinoxaline 4-oxide under these conditions yields cu-(3,4-dihydro-3-oxo-2-quinoxalinyl)aceto-phenone (204) by displacement of the cyano group by the ketone carbanion and rearrangement of the N-oxide.212... 

The enzyme is a hexamer, actually a dimer of trimers made up of 291-residue polypeptide chains.28 Aceto-acetyl-CoA is a competitive inhibitor which binds into the active site and locates it. From the X-ray structure of the enzyme-inhibitor complex it can be deduced that the carboxylate group of E144 abstracts a proton from a water molecule to provide the hydroxyl ion that binds to the P position (Eq. 13-6, step a) and that the E164 carboxyl group donates a proton to the intermediate enolate anion in step b.28 The hydroxyl group... 

Figure 18-6 Proton nmr spectrum of ethyl 3-oxobutanoate (ethyl aceto-acetate) at 60 MHz calibrations are relative to tetramethylsilane at 0.00 ppm. Peaks marked a, b, and c are assigned, respectively, to the OH, alkenyl, and methyl protons of the enol form, whereas peaks d and e are assigned to the a-CH2 and methyl protons, respectively, of the ketoform. The quartet of lines at 4.2 ppm and the triplet at 1.3 ppm result from the ethyl groups of both keto and enol forms.

Reaction XLIV. (b) Condensation of Alkyl and Aryl Halogen Compounds with the Sodio- and other Metallo-derivatives of Ethyl Aceto-acetate and its Homolognes. (A., 186, 214 201, 143 213, 143.)—Like malonic ester, acetoacetic ester contains two 1 3-carbonyl groups with a methylene group in position 2. It is only to be expected then that it yields with metallic sodium or sodium alcoholate sodio-derivatives from which mono- and di-, alkyl and aryl homologues can be obtained by treatment with a suitable halide, including halogen esters. Acetoacetic acid... 

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