WordNet

remove a carboxyl group from (a chemical compound)
lose a carboxyl group; "the compound decarboxylated"
the process of removing a carboxyl group from a chemical compound (usually replacing it with hydrogen)

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/05/06 18:00:50」(JST)

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Decarboxylation

Decarboxylation is a chemical reaction that removes a carboxyl group and releases carbon dioxide (CO₂). Usually, decarboxylation refers to a reaction of carboxylic acids, removing a carbon atom from a carbon chain. The reverse process, which is the first chemical step in photosynthesis, is called carboxylation, the addition of CO₂ to a compound. Enzymes that catalyze decarboxylations are called decarboxylases or, the more formal term, carboxy-lyases (EC number 4.1.1).

In organic chemistry

The term "decarboxylation" literally means removal of the COOH (carboxyl group) and its replacement with a proton. The term relates the state of the reactant and product. Decarboxylation is one of the oldest organic reactions, since it often entails simple pyrolysis, and volatile products distilled from the reactor. Heating is required because the reaction is less favorable at low temperatures. Yields are highly sensitive to conditions. In retrosynthesis, decarboxylation reactions can be considered the opposite of homologation reactions, in that the chain length becomes one carbon shorter. Metals, especially copper compounds,^[1] are usually required. Such reactions proceed via the intermediacy of metal carboxylate complexes.

Decarboxylation of aryl carboxylates can generate the equivalent of the corresponding aryl anion, which in turn can undergo cross coupling reactions.

Alkylcarboxylic acids and their salts do not always undergo decarboxylation readily.^[2]^[3] Exceptions are the decarboxylation of beta-keto acids, α,β-unsaturated acids, and α-phenyl, α-nitro, and α-cyanoacids. Such reactions are accelerated due to the formation of a zwitterionic tautomer in which the carbonyl is protonated and the carboxyl group is deprotonated.^[4] Typically fatty acids do not decarboxylate readily. Reactivity of an acid towards decarboxylation depends upon stability of carbanion intermediate formed in above mechanism. Many reactions have been named after early workers in organic chemistry. The Barton decarboxylation, Kolbe electrolysis, Kochi reaction and Hunsdiecker reaction are radical reactions. The Krapcho decarboxylation is a related decarboxylation of an ester. In ketonic decarboxylation a carboxylic acid is converted to a ketone.

Protodecarboxylation

Protodecarboxylations involve the conversion of a carboxylic acid to the corresponding hydrocarbon. This is conceptually the same as the more general term "decarboxylation" as defined above except that it specifically requires that the carboxyl group is, as expected, replaced by a proton. The reaction is especially common in conjunction with the malonic ester synthesis and Knoevenagel condensations. The reaction involves the conjugate base of the carboxyl group, a carboxylate ion, and an unsaturated receptor of electron density, such as a protonated carbonyl group. Where reactions entail heating the carboxylic acid with concentrated hydrochloric acid such a direct route is impossible as it would produce protonated carbon dioxide. In these cases, the reaction is likely to occur by initial addition of water and a proton.^[5]

In biochemistry

Common biosynthetic oxidative decarboxylations of amino acids to amines are:

tryptophan to tryptamine
phenylalanine to phenylethylamine
tyrosine to tyramine
histidine to histamine
serine to ethanolamine
glutamic acid to GABA
lysine to cadaverine
arginine to agmatine
ornithine to putrescine
5-HTP to serotonin
L-DOPA to dopamine

Other decarboxylation reactions from the citric acid cycle include:

pyruvate to acetyl-CoA (see pyruvate decarboxylation)
oxalosuccinate to α-ketoglutarate
α-ketoglutarate to succinyl-CoA.

Case studies

Upon heating, Δ9-Tetrahydrocannabinolic acid decarboxylates to give the psychoactive compound Δ9-Tetrahydrocannabinol.^[6] In beverages stored for long periods, very small amounts of benzene may form from benzoic acid by decarboxylation catalyzed by the presence of vitamin C.^[7] The addition of catalytic amounts of cyclohexenone has been reported to catalyze the decarboxylation of amino acids.^[8] However, using such catalysts may also yield an amount of unwanted by-products.

References

^ Richard H. Wiley and Newton R. Smith. "m-Nitrostyrene". Org. Synth. ; Coll. Vol. 4, p. 731
^ March, Jerry (1985), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (3rd ed.), New York: Wiley, ISBN 0-471-85472-7
^ http://www.chem.ucalgary.ca/courses/350/Carey5th/Ch19/ch19-3-4.html, Decarboxylation, Dr. Ian A. Hunt, Department of Chemistry, University of Calgary
^ Jim Clark (2004). "The Decarboxylation of Carboxylic Acids and their Salts". Chemguide. Retrieved 2007-10-22.
^ "Malonic Ester Synthesis". Organic Chemistry Portal. Retrieved 2007-10-26.
^ "Does marijuana have to be heated to become psychoactive?".
^ http://www.cfsan.fda.gov/~dms/benzdata.html
^ http://www.erowid.org/archive/rhodium/chemistry/tryptophan.html, Tryptamine from Tryptophan

UpToDate Contents

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English Journal

Light-Induced Ruthenium-Catalyzed Nitrene Transfer Reactions: A Photochemical Approach towards N-Acyl Sulfimides and Sulfoximines.

Bizet V1, Buglioni L, Bolm C.
Angewandte Chemie (International ed. in English).Angew Chem Int Ed Engl.2014 Apr 9. doi: 10.1002/anie.201310790. [Epub ahead of print]
1,4,2-Dioxazol-5-ones are five-membered heterocycles known to decarboxylate under thermal or photochemical conditions, thus yielding N-acyl nitrenes. Described herein is a light-induced ruthenium-catalyzed N-acyl nitrene transfer to sulfides and sulfoxides by decarboxylation of 1,4,2-dioxazol-5-ones
PMID 24719367

Diastereoselective synthesis of γ- and δ-lactams from imines and sulfone-substituted anhydrides.

Sorto NA1, Di Maso MJ, Muñoz MA, Dougherty RJ, Fettinger JC, Shaw JT.
The Journal of organic chemistry.J Org Chem.2014 Mar 21;79(6):2601-10. doi: 10.1021/jo500050n. Epub 2014 Mar 7.
Sulfone-substituted γ- and δ-lactams have been prepared in a single step with high diastereoselectivity. Sulfonylglutaric anhydrides produce intermediates that readily decarboxylate to provide δ-lactams with high diastereoselectivity. Substituents at the 3- or 4-position of the glutaric anhydride
PMID 24552208

Simultaneous recovery of benzene-rich oil and metals by steam pyrolysis of metal-poly(ethylene terephthalate) composite waste.

Kumagai S1, Grause G, Kameda T, Yoshioka T.
Environmental science & technology.Environ Sci Technol.2014 Mar 18;48(6):3430-7. doi: 10.1021/es405047j. Epub 2014 Feb 25.
The possibility of simultaneous recovery of benzene and metals from the hydrolysis of poly(ethylene terephthalate) (PET)-based materials such as X-ray films, magnetic tape, and prepaid cards under a steam atmosphere at a temperature of 450 °C was evaluated. The hydrolysis resulted in metal-containi
PMID 24527803

Japanese Journal

Single nucleotide polymorphisms of PAD1 and FDC1 show a positive relationship with ferulic acid decarboxylation ability among industrial yeasts used in alcoholic beverage production(BREWING AND FOOD TECHNOLOGY)