Synthesis of Hantzsch Ester (A1) from Ethyl Acetoacetate
High yield synthesis of nitroacetoacetate and nitroacetate esters
Synthesis of Hantzsch Ester (A1) from Ethyl Acetoacetate
Alkylation at the -carbon of ethyl acetoacetate via an alkali metal enolate and subsequent removal of the ester group by sequential hydrolysis and decarboxylation provides a classical synthesis of methyl ketones (eq 1). The ambident reactivity of the acetoacetate anion often causes competing - and -alkylations. The extent of vs.
In the liver, most of the acetyl-CoA obtained from fatty acid oxidation is oxidized by the citric acid cycle. However, some of the acetyl-CoA is used to synthesize a group of compounds known as : acetoacetate, β-hydroxybutyrate, and acetone. Two acetyl-CoA molecules combine, in a reversal of the final step of β-oxidation, to produce acetoacetyl-CoA. The acetoacetyl-CoA reacts with another molecule of acetyl-CoA and water to form β-hydroxy-β-methylglutaryl-CoA, which is then cleaved to acetoacetate and acetyl-CoA. Most of the acetoacetate is reduced to β-hydroxybutyrate, while a small amount is decarboxylated to carbon dioxide and acetone.
Benzyl acetoacetate for synthesis
This problem can be overcome by employing -methoxy--methyl amides (see ) as acylating agents. Addition of catalytic amounts of greatly improves the efficiency of acylation of dilithio ethyl acetoacetate (eq 10). -Dimethyl carboxamides can also be used as acylating agents in the presence of .Knoevenagel condensation of acetoacetates with carbonyl compounds may be carried out using a wide range of catalysts and reaction conditions. A particularly mild and efficient procedure involves the use of and pyridine in THF at low temperatures, which allows the condensation of ethyl acetoacetate with aliphatic, aromatic, and heteroaromatic aldehydes to produce -alkylideneacetoacetates (eq 11). The condensation of -butyl acetoacetate with aldehydes and subsequent cleavage of the -butyl ester by heating with catalytic provides a convenient synthesis of ,-unsaturated methyl ketones. -Alkyl-substituted acetoacetates can add to aldehydes; however, the adducts often undergo acyl cleavage under the reaction conditions to give ,-unsaturated
1,5-Diketones produced by the conjugate addition of acetoacetates to ,-unsaturated ketones are useful in the synthesis of cyclohexenones via intramolecular aldol condensation. A sequence of Knoevenagel condensation, Michael addition, aldol cyclization, and dealkoxycarbonylation may be carried in one pot using ethyl acetoacetate, an aliphatic aldehyde, and catalyst (eq 15). In general, however, annulation reactions of acetoacetates involve the Michael addition and the aldol cyclization as two separate steps (eq 16).Successive silylation of methyl acetoacetate with gives the mono- and the bis(trimethylsilyl) enol ethers (eq 17), which are useful as synthetic equivalents of acetoacetate in reactions with a variety of electrophiles.
Synthesis of Ethyl Acetoacetate - YouTube
Highly enantioselective asymmetric hydrogenation of acetoacetates can be achieved using -ruthenium complexes (eq 21). The resulting 3-hydroxybutanoates (see ) are versatile auxiliaries and building blocks for the synthesis of enantiomerically pure products.
The classical synthesis of coumarins via the von Pechmann reaction involves the condensation of acetoacetates with phenols under acid catalysis (eq 22). Chromones are produced when the phenol contains a deactivating group or the acetoacetates are -substituted.
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The condensation of acetoacetates with anilines can give either 2-hydroxy- or 4-hydroxyquinolines, depending upon the reaction temperature. In the Hantzch synthesis of symmetrical dihydropyridines, two equivalents of acetoacetates are condensed with aldehydes in the presence of (eq 23). A variation of the Hantzch synthesis for the preparation of unsymmetrical dihydropyridines involves the condensation of -(alkylidene)acetoacetates with 3-aminocrotonate.
METHYL ACETOACETATE | C5H8O3 ..
Section 21.6The acetoacetic estersynthesisis a procedure in which ethyl acetoacetate is alkylated with an alkyl halide as the first step in the preparation
Amino Acid Synthesis and Metabolism
Section 21.7The malonic estersynthesisis related to the acetoacetic ester synthesis. Alkyl halides (RX) are converted to carboxylic acids of the type
Quick revisions | Biochemistry for Medics – Lecture Notes
The acetoacetate and β-hydroxybutyrate synthesized by the liver are released into the blood for use as a metabolic fuel (to be converted back to acetyl-CoA) by other tissues, particularly the kidney and the heart. Thus, during prolonged starvation, ketone bodies provide about 70% of the energy requirements of the brain. Under normal conditions, the kidneys excrete about 20 mg of ketone bodies each day, and the blood levels are maintained at about 1 mg of ketone bodies per 100 mL of blood.
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