Carboxy-inversion

Diacyl peroxides may also undergo non-radical decomposition via the carboxy inversion process to form an acylcarbonate (Scheme 3.27).46 The reaction is of greatest importance for diaroyl peroxides with electron withdrawing substituents and for aliphatic diacyl peroxides (36) where R is secondary, tertiary or ben/,yl.157 The reaction is thought to involve ionic intermediates and is favored in polar solvents 57 and by Lewis acids.158 Other heterolytic pathways for peroxide decomposition have been described.150... 

Another carboxy inversion reaction has been noted in the case of di-triptoyl peroxide decomposing in benzene.118... 

Benzoyl peroxide appears to decompose entirely by the radical mechanism, the reaction being rather insensitive either to solvent changes or to the addition of acid catalysts. The unsymmetrical peroxide, -methoxy-/> -nitrobenzoyl peroxide, behaves quite differently. It will decompose either by the polar mechanism or by the radical mechanism.821 The radical mechanism prevails in benzene and the acids produced are -nitrobenzoic and anisic in equal amounts. In the more polar solvents anisic acid is formed to a lesser extent than is >-nitrobenzoic acid, because the carboxy inversion reaction (rearrangement) competes successfully. The reaction is subject to acid catalysis... 

The Claisen rearrangement of lactonic enolates provides a new route to cycloalkenes. Cyclocitral was converted to the lactone (642) through a multistep sequence, the lactone deprotonated with LDA in THF at -78 °C, and the enolate quenched with f-butyldimethyl-chlorosilane (80JA6889, 6891). The crude ketene acetal (643) was heated at 110 °C for 10 h, and the product treated with fluoride ion to afford a single acid. Replacement of the quaternary carboxyl group by hydroxyl was accomplished through use of the carboxy inversion reaction (Scheme 147). The product (645) of this last reaction was identical with an authentic sample of widdrol in all respects excluding its optical rotation. 

As is the case in conventional solvents, competing radical and ionic processes (Scheme 4.8) were needed to explain the observed products and reaction kinetics in the decomposition of diacyl peroxides in sc C02 (Sigman et al., 1987). In addition to ArC02R and other products attributable to free-radicals, carboxy inversion products were observed, which result from ionization of the diacyl peroxide (Scheme 4.8). 

Hnally, a useful, although not strictly a radical, meAod of effecting decarboxylative oxygenation is Ae so-called carboxy inversion reaction. The activated acid is transformed into a mixed all l aryl diacyl peroxide which suffers decarboxylative rearrangement to Ae alkyl ester of the aryl acid. This reaction is particularly useful as it takes place wiA retention of configuration at the migrating center (equation... 

Carboxy-inversion reaction. Denney and Sherman found that m-chloroperbenzoic acid (2) reacts readily with a carboxylic acid chloride (1) in hexane solution at 0 in the presence of pyridine to form a mixed peroxide (3). When the mixture is stirred for several hours at room temperature the peroxide rearranges to the mixed carbonate... 

Diacyl peroxides, which are known as radical sources, can decompose by an ionic mechanism in the presence of strong acids. Thus, benzoyl peroxide 282 can be converted into phenyl benzoate in a process whose first step involves a Lewis acid catalyzed carboxy inversion reaction to the mixed carbonate 283 (equation 134). ... 

The carboxy inversion of diacyl peroxides has been interpreted as being an ionic reac-... 

Peroxyesters may undergo non-radical decomposition via the Criegee rearrangement (Scheme 3.35). This process is analogous to the carboxy inversion process described for diacyl peroxides (see 3.3.2.1.3) and probably involves ionic intennediates. 

Inversion s. Carboxy-inversion and under Configuration lodacetone as hydrogen iodide scavenger 21, 966 Iodides (s. a. Halides, Replacement)... 

Without additional reagents Carboxy-inversion of acyl peroxides... 

Wittig elaboration and ketone reduction, ester hydrolysis, acetylation and treatment with dicyclohexylcarbodiimide and m-chloroperbenzoic acid afforded the mixed peranhydride (26b). Transformation of (26b) to (3b) was achieved by means of a carboxy inversion reaction which occurred, with retention of configuration, on refluxing in acetonitrile, and treatment of the resulting mixed carbonate with lithium methoxide. 

Ethers can be cleaved rapidly at room temperature by diborane and halogen 0-Demethylation with retention of O-tosyl groups can be achieved with boron trichloride Alcohols can be obtained by degradation of carboxylic acids through carboxy-inversion of acyl peroxides . Aldehydes can be efficiently decarbonylated under mild conditions in the presence of a rhodium complex . A new mild and potentially selective method for the prepn. of aliphatic... 

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