A-Keto-//-dicarboxylic acid

Wittig-Smiles reaction.l The reaction of a triarylmethylphosphonium halide and a base with an a-keto dicarboxylic acid halide imide such as 1 results in a Wittig reaction followed by a Smiles rearrangement to provide a pyrrolidine dione... 

Oxalacetic acid esters s. a-Keto-/ -dicarboxylic acid esters... 

Oxalacetic acid esters s. a-Keto-/ -dicarboxylic acid esters Oxalic acid as reagent 16, 253 18, 231, 332, 604... 

One of the most actively investigated aspects of enamine chemistry has been the acylation process (i). Initial intensive studies by Hiinig (373-375) showed the ease of preparing a variety of 9-diketones and particularly the synthetic potential of acylated cyclic ketones as intermediates in the preparation of aliphatic keto acids, keto dicarboxylic acids and diketo dicarboxylic acids (376-378). 

Method. The keto acid residue is dissolved in 1.0 ml of 2,4-dinitrophenylhydrazine (prepared by dissolving 500 /rmoles in 100 ml of 2.0 Nhydrochloric acid at 40 °C stable for 2 weeks) and left to stand for 30 min at 30 °C. A minimum of a four-fold molar excess of 2,4-dinitrophenylhydrazine is required for stoichiometric conversion of the keto acid into the hydrazone. The reaction is complete in 5 min for keto monocarboxylic acids, and in ca. 20 min for keto dicarboxylic acids. The hydrazones may be extracted from the reaction mixture with ethyl acetate. An aliquot portion of this solution is subjected to TLC. 

Structures 64 and 65 were proposed in [7] for the product from the condensation of isatin 7 with acetoacetic acid (a P-keto acid). The first must clearly be preferred, since the CH2 group must be more active than CH3 under the conditions of the Pfitzinger reaction. Actually in [21] the structure of the product 64 was proved by its oxidation to the tricarboxylic acid 66, which was also synthesized from the keto dicarboxylic acid 67 and isatin 7. 

We saw in Section 19.1 that it is harder to remove a proton from an a-carbon if the electrons are delocalized onto the carbonyl group of an ester rather than onto the carbonyl group of a ketone. For the same reason, a higher temperature is required to decarboxyiate a 8-dicarboxylic acid such as malonic acid than to decarboxyiate a jS-keto acid. 

Melichercik, M. Mrakavova, M. Nagy, A. Olexova, A. Treindl, L. 1992. Permanganate Oscillators with Keto Dicarboxylic Acid, J. Phys. Chem. 96, 8367-8368. 

Apart from reductive amination and the reaction of -keto acid derivatives with ammonia or amines, there are other carbonyl derivatives that can serve as precursors to amino acids. One sequence begins with the conversion of a,co-dicarboxylic acids... 

This reaction consists of the condensation of two molecular equivalents of a 1,3 diketone (or a J3-keto-ester) with one equivalent of an aldehyde and one of ammonia. Thus the interaction of ethyl acetoacetate and acetaldehyde and ammonia affords the 1,4-dihy dro-pyridine derivative (1), which when boiled with dilute nitric acid readily undergoes dehydrogenation and aromatisation" to gb e the diethyl ester of collidine (or 2,4,6-trimethyl-pyridine-3,5 dicarboxylic acid (II)). For the initial condensation the solid aldehyde-ammonia can conveniently be used in place of the separate reagents. 

Section 19 17 11 Dicarboxylic acids (malonic acids) and p keto acids undergo thermal decarboxylation by a mechanism m which a p carbonyl group assists the departure of carbon dioxide... 

Semmler and Risse have studied the oxidation of cedrene by means of ozone. They obtained the keto-acid, Cj Hj Oj, which on further oxidation either by means of bromine or nitric acid yields a dicarboxylic acid. 

The autoxidation of cyclic ketones with dirhenium decacarbonyl under basic catalytic conditions produces dicarboxylic acids (68-73%) bicyclic ketones are converted into keto carboxylic acids and, when one ring is aromatic, quinones are obtained, e.g. 1-tetralone produces 2-hydroxy-1,4-naphthaquinone (93%), and H02C(CH2)4C0(CH2)3C02H (85%) is obtained from 1-decalone via a cyclic triketone [5]. 

This enzyme [EC 3.5.1.3] catalyzes the hydrolysis of a monoamide of a dicarboxylic acid to generate a dicarbox-ylate and ammonia. The enzyme can utilize as a substrate glutaramate, succinamate, and their corresponding 2-keto derivatives. 

Dieckmann Condensation The intramolecular equivalent of a Claisen condensation where dicarboxylic acid ester undergoes base-catalyzed cyclization to form a P-keto ester. 

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