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Ketonic decarboxylation (also known as decarboxylative ketonization) is a type of organic reaction and a decarboxylation converting two equivalents of a carboxylic acid (R−C(=O)OH) to a symmetric ketone (R 2 C=O) by the application of heat.
The reaction mechanism is as follows. [18] Please note that any of several branched-chain α-ketoacids could have been used as a starting material; for this example, α-ketoisovalerate was arbitrarily chosen as the BCKDC substrate. NOTE: Steps 1 and 2 occur in the E 1 domain. STEP 1: α-ketoisovalerate combines with TPP and is then decarboxylated.
Decarboxylation is a chemical reaction that removes a carboxyl group and releases carbon dioxide (CO 2). Usually, decarboxylation refers to a reaction of carboxylic acids , removing a carbon atom from a carbon chain.
This was a result of the fact that any halide anion generated in the reaction inhibited the Cu-catalyzed decarboxylation process. [15] Further optimization of the system and catalyst conditions has made decarboxylative cross-coupling using bimetallic Pd–Cu systems applicable to organic synthesis, most predominantly in the formation of biaryls ...
By decarboxylation of carboxylic anhydride. Ketones can be prepared from haloketones in reductive dehalogenation of halo ketones. In ketonic decarboxylation symmetrical ketones are prepared from carboxylic acids. [10] [17] Hydrolysis of unsaturated secondary amides, [18] β-Keto acid esters, [10] or β-diketones (the acetoacetic ester synthesis).
In contrast to the relatively facile decarboxylation of β-keto acids, the decarboxylation of α-keto acids presents a mechanistic challenge. Thiamine pyrophosphate (TPP) provides the biochemical and enzymological answer. TPP is the key catalytic cofactor used by enzymes catalyzing non-oxidative and oxidative decarboxylation of α-keto acids.
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The reaction mechanism involves the acylation and activation of the acid 1 to the mixed anhydride 3. The amide will serve as a nucleophile for the cyclization forming the azlactone 4. Deprotonation and acylation of the azlactone forms the key carbon-carbon bond. Subsequent ring-opening of 6 and decarboxylation give the final keto-amide product ...