Carboxylate radical anion

DR. ESPENSON Carboxylate radical anion from radiation chemistry ought to be well set up in the formation of carbonate ion to meet just this requirement. Yet I m under the impression that the carboxylate radical anion doesn t react with perchlorate. 

Flyunt R, Schuchmann MN, von Sonntag C (2001) Combination vs. proton-catalysed disproportionation of the carboxyl radical anion, CCV-, in aqueous solution. Chem Eur J 7 796-799 Fojtik A, Czapski G, Flenglein A (1970) Pulse radiolytic investigation of the carboxyl radical in aqueous solution. J Phys Chem 74 3204-3208... 

Faster protonation rates were observed in the self-protonation of aromatic carboxylic radical anions (kprot > 10 m s ) [216] and (R)-(—)-l,l -biphenyl-2,2 -diyl hydrogen phosphate radical anion (kprot = 5.7 x 10 m s ) [217]. 

The generated radical anion can react as a nucleophile attacking the CO, and yielding a carboxylated radical anion further electrochemically reduced... 

The anodic oxidation of the carboxylate anion 1 of a carboxylate salt to yield an alkane 3 is known as the Kolbe electrolytic synthesis By decarboxylation alkyl radicals 2 are formed, which subsequently can dimerize to an alkane. The initial step is the transfer of an electron from the carboxylate anion 1 to the anode. The carboxyl radical species 4 thus formed decomposes by loss of carbon dioxide. The resulting alkyl radical 2 dimerizes to give the alkane 3 " ... 

This has been applied to the cyclization of dihalides [45, 46], nonconjugated, unsaturated ketones [47] and esters [48], oxoalkylpyridinium salts [49], aldehydes and unsaturated nitriles [50], halides, and unsaturated esters [51], The umpoled acceptors, mostly radical anions or carban-ions (see Scheme 1), can also be used in intermolecular reactions such as acylation, alkylation, or carboxylation (Eq. 5). 

Formally related reactions are observed when anthracene [210] or arylole-fines [211-213] are reduced in the presence of carboxylic acid derivatives such as anhydrides, esters, amides, or nitriles. Under these conditions, mono- or diacylated compounds are obtained. It is interesting to note that the yield of acylated products largely depends on the counterion of the reduced hydrocarbon species. It is especially high when lithium is used, which is supposed to prevent hydrodimerization of the carboxylic acid by ion-pair formation. In contrast to alkylation, acylation is assumed to prefer an Sn2 mechanism. However, it is not clear if the radical anion or the dianion are the reactive species. The addition of nitriles is usually followed by hydrolysis of the resulting ketimines [211-213]. 

In a related study, the oxidation-reduction sequence was carried out in the presence of an olefin (Scheme 21). Two products were formed. The major product resulted from the net reduction of the carboxylic acid to an aldehyde. The minor product resulted from trapping of the radical anion intermediate generated from the reduction reaction by the olefin. It should be noted that, in the absence of a trapping group, the acid can be selectively reduced to the aldehyde without any over-reduction. Although not in the scope of this review, this is a very useful transformation in its own right [35]. At this time, the yields of the cyclized products from the cyclization reaction of the radical anion with the olefin remain low. 

RADICAL ANION ARYLATION, 58, 134 Raney nickle, 57, 19, 58, 114, 116 Raney nickel,W-2, 56, 16, 74 Reduction, carboxyl groups, 56,83 Reductive alkylation, 56, 52 Resolution of amines, 55, 80, 83 Rexyn 201, 55,4 Rhodium(III) oxide, 57,1 Ring contraction, 56. 107... 

The electrocarboxylation of aldehydes and ketones leads to the corresponding a-hydroxycarboxylic acids that can easily be converted into carboxylic acids via a hydrogenation reaction [7]. It has been reported that the electrocarboxylation of aromatic ketones occurs through the reaction of C02 onto the activated carbon atom of the carbonyl group of the ketyl radical anion generated upon electron transfer to the ketone [7]. Otherwise, the aforementioned intermediate is likely to be a resonance hybrid (see Equation 12.23), and its electrophilic reaction with C02 may take place both at the carbon or the oxygen atom [42, 43]. 

Photoinduced carboxylation of aromatic hydrocarbons via their radical anions in the presence of tertiary amines has been reported by Tazuke and Ozawa [404], Similar photofixation of carbon dioxide on styrene has been reported Toki et al. [405], In these photoreactions, the anionic part of the radical anions are trapped by electrophiles such as proton and carbon dioxide (Scheme 119). 

Both, strained and unsaturated organic molecules are known to form cation radicals as a result of electron transfer to photoexdted sensitizers (excited-state oxidants). The resulting cation radical-anion radical pairs can undergo a variety of reactions, including back electron transfer, nucleophilic attack on to the cation radical, electrophilic attack on the anion radical, reduction of anion radical, and addition of anion radical to the cation radical. This concept has been nicely demonstrated by Gassman et al. [103, 104], using the photoinduced electron-transfer cydization of y,8-unsatu-rated carboxylic add 232 to y-ladones 233 and 234 as an example (see Scheme 8.65). 

Photoinduced electron transfer from the carboxylate ion to the excited triplet phthalimide (fcT = 293-300 kj mol-1) appears to be followed by a rapid protonation of the radical anion and cyclization via a biradical recombination reaction (Scheme 9.1). Acetone (which also acts as photosensitizer) containing a small amount of water is the solvent of choice, whereas potassium carbonate is the ideal base to enhance cyclization versus simple decarboxylation and ring opening of the phthalimide [4]. 

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