Decarboxylation, catalytic

Decarboxylation designates the loss of a carboxyl group, as a result of enzymatic microbial activity. For example, the carboxyl group of aliphatic carboxylic acids differentially degrades the molecule (Fig. 15.4). In a subsurface environment characterized by extensive microbial activity, catalytic decarboxylations for both naturally occurring and exogenous organic compounds may occur. 

Catalytic decarboxylation processes occur in aliphatic keto acids in which the keto group is in an a-position to one carboxyl group and in a P-relationship to another. Thus, the normal decarboxylation of a p-keto acid is facilitated by metal coordination to the a-keto acid moiety. The most-studied example is oxaloacetic acid and it has been shown that its decarboxylation is catalyzed by many metals following the general order Ca2+ < Mn2+ < Co2+ < Zn2+ < Ni2+ < Cu2+ < Fe3+ < Al3"1".66 67 The overall rate constants can be correlated with the stability constants of 1 1 complexes of oxalic acid rather than oxaloacetic acid, as the uncoordinated carboxylate anion is essential for the decarboxylation. The generally accepted mechanism is shown in Scheme 15. Catalysis can be increased by the introduction of x-bonding ligands, which not only increase the... 

A higher selectivity is experienced in the photolysis of phenyldimethylglycidic acid. In this case also, the catalytic decarboxylation is followed by Isomerization to a carbonyl compound (Eq, 362). ... 

In the authors judgment, catalytic action in the strict sense of the term, implying regeneration of the catalyst, has been rigorously proven in two cases. With other reactions, however, true catalysis has not been unequivocally established. Michaelis-Menten kinetics, indicative of the formation of a substrate-polymer complex, has been shown with each type of reaction. Some of the activities have been very weak, with reaction times for incomplete conversion of substrate measured in days. Others, although not as rapid as enzyme-catalyzed rates, are relatively fast, e.g., the catalytic decarboxylation of OAA by equimolar amounts of lysine residue in polymeric form was over 90% complete in less than 1 hour. 

Decarboxylation, a-Imino acids undergo catalytic decarboxylation in the presence of BU3P (catalytic quantities) at room temperature. Acetic acid or pyridine can accelerate the process. 

Goossen LJ, Deng G, Levy LM (2006) Synthesis of biaryls via catalytic decarboxylative coupling. Science 313 662-664... 

Although thiamine, a thiazolium salt, contains a pyrimine ring, it is the thiazole ring that is responsible for its biological action, thiamine dihosphate being the coenzyme of decarboxylases. The mechanism of the catalytic decarboxylation (e.g. of pyruvic acid to acetaldehyde) was interpreted by Breslow in 1958. The active species is the N-ylide 12 formed from thiamine diphosphate and basic cell components ... 

Contrary to aryl carobxylates, benzyl carboxylates generally undergo type a scission. However, the pyridinomethyl esters also effectively guide the bond cleavage of type b probably via intramolecular coordination (Scheme 3.35) [67]. Since decarbonylation from the resulting acyl group rapidly occurs in this system, catalytic decarboxylation takes place in the presence of ammonium formate as a hydride source. 

Besides the synthesis of various triazoles, the synthetic potential of the copper flow system was further demonstrated by the catalytic decarboxylation of the propargyhc add 11 (Scheme 4, Reaction 2) and the C—O coupling in the synthesis of benzopyranone 14 (Scheme 4, Reaction 3) (2010SL2009). 

Maki-Arvela P. Kubickova I, Eranen K, Snare M. Murzin D. Catalytic decarboxylation of fatty acids and their derivatives. Energy Fuels 2007 21 30. 

Zweifel and Deuel 108a) have recently demonstrated the catalytic decarboxylation of uronic acids with heavy metal ions under slightly acidic... 

Synthetic highlights The Cu-promoted catalytic decarboxylative, biaryl synthesis of valsartan is an example of biomimetic, aerobic decarboxylation and enables C-C bond formation in aqueous solution. The chiral variant of biaryl synthesis is exemplified by the stereoselective approach to the axially chiral biaryl system present in vancomycin. 

Cu-Promoted Catalytic Decarboxylative Biaryl Synthesis, a Biomimetic Type Aerobic Decarboxylation... 

Scheme 5 First design of a catalytic decarboxylative cross-coupling...

SciFinder search 27 January 2012, catalytic decarboxylative coupling, publication years 2006-2012, duplicates and enzymatic reactions removed... 

Alkynyl acids also underwent analogous decarboxylation facilely [75]. These decarboxylation processes have been extended to catalytic decarboxylative transformations (Chapter 4). 

During the early 1990s, Kaeriyama s group contributed to this field when they reported the synthesis of the ester derivative of PPP, 26, which was used as a precursor for parent PPP [79-81] (Fig. 8.12). Hydrolysis of the ester functions in 26 afforded the free acids, which were catalytically decarboxylated using copper(II) oxide, basic copper(II) carbonate, and copper(I) oxide. 

Block copolymers comprising carbonate and arylene ether blocks have been prepared by the catalytic decarboxylation of random or alternating copolycarbonates. This novel route to block copolymers is catalyzed by a number of catalysts and requires only that one of the bisphenols in the starting copolycarbonates be activated by electron-withdrawing substituents, e.g. 4,4 -dihydroxydiphenyl sulfone (bisphenol S), or 4,4 -dihydroxybenzophenone (bisphcnol K). 

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