Carbon-oxygen 1,1-insertion

Methyl ketones give esters of acetic acid that is oxygen insertion occurs between the carbonyl carbon and the larger of the two groups attached to it... 

A related situation is found in the case of P-substituted cycloketones here, the electronic difference between the two a-carbons is almost insignificant, resulting in unselective migration upon chemical oxidation. BVMOs have a particularly different behavior, as they can influence the stereo- and/or regioselectivity of the biooxidation. In the latter case, the distribution of proximal and distal lactones is affected by directing the oxygen insertion process either into the bond close or remote to the position of the P-substituent. Consequently, a regioisomeric excess (re) can be defined for this biotransformation, similar to enantiomeric excess or diastereomeric excess values [143]. 

The Baeyer-Villiger oxidation reaction was discovered more than 100 years ago by Adolf von Baeyer and Victor Villiger. By this reaction, ketones are converted into the corresponding esters. In organic chemistry, peracids are commonly used as catalyst to perform this atypical oxidation reaction that results in oxygen insertion into a carbon—carbon bond (Fig. 1). 

During the insertion mechanism, the metal is inserted into the carbon-oxygen bond. The insertion is promoted by a strong metal—oxygen interaction. It is thought that unreduced metal ions may play an important role in the insertion mechanism (electrophilic catalysis). The type of the catalyst, the method of preparation, and the additives can influence the concentration and stability of these ions. 

Reinhold and Bruni studied the metabolism of 7,9-dideuterioellipticine (17) in rats and found that deuterium originally at position 9 was completely lost during the mammalian hydroxylation process (147). Proton and carbon-13 NMR and mass spectral analyses confirmed the complete elimination of deuterium at position 9, thus ruling out the occurrence of an NIH shift mechanism in the hydroxylation of ellipticine. An oxygen-insertion process was rationalized to account for the mechanism of aromatic hydroxylation in rats since this would not be expected to display the NIH shift but should demonstrate an isotope effect. It was... 

On the other hand, when the oxidative carbonylation of a ,a -disubstituted propynylamines was carried out in the presence of an excess of CO2, the intermediate carbamate species could undergo cyclization with incorporation of CO2 into the five-membered cycle, either by direct nucleophilic attack of the carbamate oxygen to the triple bond coordinated to Pd(II) (Scheme 33, path a) or through the intermediate formation of a palladium carbamate complex followed by triple bond insertion (Scheme 33, path b). Carbon monoxide insertion into the Pd - C bond of the resulting stereoisomeric vinylpalladium intermediates then led to the final oxazolidi-none derivatives. 

Following our first report on the palladium-catalyzed reaction of vinyl triflates with olefins (Heck-type reaction), oxidative insertion of palladium(O) into the carbon-oxygen bond of easily available vinyl triflates ... 

Metal Hydrides. The simplest reactions in this group are the various catalytic reduction reactions of carbon monoxide. Methane or higher hydrocarbons, methanol or higher alcohols, and a variety of other oxygenated organic compounds may be formed, depending upon the catalyst and reaction conditions (23). There is little evidence about the mechanism of these reactions, but the initial step in every example is probably a carbon monoxide insertion into a metal hydride, followed by reduction reactions. 

The Baeyer-Villiger oxidation of ketones represents a powerful synthetic method that breaks carbon-carbon bonds in an oxygen insertion process to deliver lactones. A recent comprehensive review by ten Brink et describes the different... 

Aromatic dicarboximides behave in a different way on irradiation with aikenes. Instead of cycloaddition to the carbon-oxygen double bond, the overall reaction gives a product in which the alkene is inserted between the nitrogen atom and one of the carbonyl groups (4.78). The reaction is stereospecific, and the mechanism may... 

There are two reasonable structural results of C02 insertion since the metal-ligand pair may add across the carbon-oxygen double bond in two different ways yielding (29) or (30), depending in part on the polarity of the M—X bond. 

A significant rate enhancement for the C02 insertion process was noted in the presence of alkali metal counterions (Table I), even in the highly coordinating THF solvent. This rate acceleration was not, however, catalytic in alkali metal counterion, since the once formed carboxylate was observed to form a tight ion pair (76, 77) via its uncoordinated oxygen atom with the alkali metal ion, as evinced by infrared spectroscopy in the v(C02) region. That is, the counterion was consumed during the carbon dioxide insertion reaction. 

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