Oxidative decarboxylation of acids

Oxidation of carboxylic acids alone and in hydrocarbon solution is accompanied by the production of C02 [204—215], Carbon dioxide is formed from the carboxylic group, as established by the tracer technique [204-210], Oxidation of R14COOH yields 14C02 [204-209] and that of RC18OOH produces C1802 [210], 

Carboxylic acids decarboxylate in oxidizing cumene at 80°C, whereas, in the absence of oxygen, they decarboxylate only above 300° C [208], The reaction of peroxy radicals with carboxylic groups was suggested to account for C02 formation, viz. 

But carboxylation can also proceed by reaction of the peroxy radical with the —CH2 group, viz. 

Other evidence for peroxy radical reaction with the carboxylic group is 

When the hydrocarbon oxidizes with a constant initiation rate, [R02 ] = const. = y/W /2kt and 

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Oxidative decarboxylation of acids to alkenes is often accompanied by alkene rearrangement. Lukas... 

R. A. Sheldon and J. K. Kochi, Oxidative Decarboxylation of Acids by Lead Tetraacetate, Organic Reactions 19, 279 (1972). 

Oxidative deearboxyUttian of acids (1, 554-557 2, 235-237 3, 168-169). The oxidative decarboxylation of acids by lead tetraacetate has been reviewed by Sheldon and Kochi. ... 

Imidazoles normally undergo free-radical reactions at the 2-position. For example, homolytic free-radical alkylation of histidines and histamines yields 2,3-disubstituted histidines and histamines. In these reactions, the free radical was generated via silver-catalyzed oxidative decarboxylation of acids with peroxydisulfate 433 (Scheme 103) <2001BML1133>. 

Sheldon, R. A., Kochi, J. K. Oxidative decarboxylation of acids by lead tetraacetate. Org. React. 1972,19, 279-421. 

Oxidative decarboxylation of acids to alkenes is often accompanied by alkene rearrangement. Lukas J. Goossen of the Max-Planck-lnstitut, Muhlheim, has found (Chem. Commun. 2004, 724) that in situ activation of the acid with phthalic anhydride and inclusion of the bis phosphine DPE-Phos substantially slow alkene isomerization, which can be essentially eliminated by running the reaction to only 80% conversion. Both linear and branched carboxylic acids work well. 

Miscellaneous Reactions.—second method for the oxidative decarboxylation of acids has appeared this year see also ref. 335. Thus, 5-cndo-norborn-2-ene carboxylic acid on conversion to its dianion and reaction with molecular oxygen affords the a-hydroperoxide. The hydroperoxide is decomposed to 5-norbomen-2-one by reaction with p-toluenesulphonic acid or by reaction with dimethylformamide dimethyl-acetal. 

This convenient C-alkylation is performed with radicals generated by Ag-catalyzed oxidative decarboxylation of acids by peroxydisulfate. Due to the nucleophilic... 

Anderson JM, Kochi JK (1970a) Manganese(III) complexes in oxidative decarboxylation of acids. J Am Chem Soc 92 2450-2460... 

Regioselectivity of C—C double bond formation can also be achieved in the reductiv or oxidative elimination of two functional groups from adjacent carbon atoms. Well estab llshed methods in synthesis include the reductive cleavage of cyclic thionocarbonates derivec from glycols (E.J. Corey, 1968 C W. Hartmann, 1972), the reduction of epoxides with Zn/Nal or of dihalides with metals, organometallic compounds, or Nal/acetone (seep.lS6f), and the oxidative decarboxylation of 1,2-dicarboxylic acids (C.A. Grob, 1958 S. Masamune, 1966 R.A. Sheldon, 1972) or their r-butyl peresters (E.N. Cain, 1969). 

Synthetic phenol capacity in the United States was reported to be ca 1.6 x 10 t/yr in 1989 (206), almost completely based on the cumene process (see Cumene Phenol). Some synthetic phenol [108-95-2] is made from toluene by a process developed by The Dow Chemical Company (2,299—301). Toluene [108-88-3] is oxidized to benzoic acid in a conventional LPO process. Liquid-phase oxidative decarboxylation with a copper-containing catalyst gives phenol in high yield (2,299—304). The phenoHc hydroxyl group is located ortho to the position previously occupied by the carboxyl group of benzoic acid (2,299,301,305). This provides a means to produce meta-substituted phenols otherwise difficult to make (2,306). VPOs for the oxidative decarboxylation of benzoic acid have also been reported (2,307—309). Although the mechanism appears to be similar to the LPO scheme (309), the VPO reaction is reported not to work for toluic acids (310). 

Alkyl radicals produced by oxidative decarboxylation of carboxylic acids are nucleophilic and attack protonated azoles at the most electron-deficient sites. Thus imidazole and 1-alkylimidazoles are alkylated exclusively at the 2-position (80AHC(27)241). Similarly, thiazoles are attacked in acidic media by methyl and propyl radicals to give 2-substituted derivatives in moderate yields, with smaller amounts of 5-substitution. These reactions have been reviewed (74AHC(i6)123) the mechanism involves an intermediate cr-complex. 

Other interactions of /3-lactams with electrophiles include the oxidative decarboxylation of the azetidin-2-one-4-carboxylic acid (85) on treatment with LTA and pyridine (81M867), and the reaction of the azetidin-2-one-4-sulfinic acid (86) with positive halogen reagents. This affords a mixture of cis- and trans-4-halogeno-/3-lactams (87), the latter undergoing cyclization to give the bicyclic /3-lactam (88) (8UOC3568). 

Van Tamelen (I24a) has reported a useful and specific synthetic method for the production of enamines by the oxidative decarboxylation of N,N-dialkyl a-amino acids with sodium hypochlorite. 

The first stage of the reaction is a special case of the oxidative decarboxylation of amino acids, for which two general mechanistic hypotheses are under discussion.This is followed by aromatiz-ation. A possible mechanism (241- 242- 243- 245) has been... 

TPP-dependent enzymes are involved in oxidative decarboxylation of a-keto acids, making them available for energy metabolism. Transketolase is involved in the formation of NADPH and pentose in the pentose phosphate pathway. This reaction is important for several other synthetic pathways. It is furthermore assumed that the above-mentioned enzymes are involved in the function of neurotransmitters and nerve conduction, though the exact mechanisms remain unclear. 

In another type of oxidative decarboxylation, arylacetic acids can be oxidized to aldehydes with one less carbon (ArCH2COOH ArCHO) by tetrabutylammonium... 

Figure 17-5. Oxidative decarboxylation of pyruvate by the pyruvate dehydrogenase complex. Lipoic acid is joined by an amide link to a lysine residue of the transacetylase component of the enzyme complex. It forms a long flexible arm, allowing the lipoic acid prosthetic group to rotate sequentially between the active sites of each of the enzymes of the complex. (NAD nicotinamide adenine dinucleotide FAD, flavin adenine dinucleotide TDP, thiamin diphosphate.)...

Summarizing the results obtained by controlled potential electrolysis and polarography, the reaction process for the electrolytic evolution of CO2 was estimated to be as follows the first step was one electron transfer from DMFC in NB to FMN in W as in Eq. (7). The second step was the catalytic reduction of O2 by FMNH as in Eq. (8). The final step was the oxidation of pyruvic acid by the reduction product of O2, H2O2, in W as in Eq. (9), well-known as an oxidative decarboxylation of a-keto acids [43] ... 

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