Oxygen insertions

Baeyer-Villiger Oxidation- oxidation of ketones to esters and lactones via oxygen 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]. 

How does oxygen insert in between the B—bonds Let s take a closer look at the reagents— a hydroxide ion can deprotonate hydrogen peroxide to form a hydroperoxide anion ... 

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). 

Oxygen sssoclated with Mo responsible for oxygen Insertion Into the allyllc Intermediate... 

To test for the presence of hydrogen, inject the gas to be tested into bubble solution. The resulting bubbles should ignite easily. To test for the presence of oxygen, insert a glowing splint into the gas. The splint should immediately ignite. In this lab, you will discover what happens when an electric current is passed through water. 

The oxygen insertion reaction can be extended to tungsten-hydridosilanes, which are noteworthy in that reaction (2) not only affords the silanol 12a, but also the double and even triple oxygenation products 12b,c starting from Cp (OC)2(Me3P)W-SiRH2 (R = H, Me) (11a,b). 

This view is supported by the formation of alcohols and aldehydes, which is not possible via mechanism 1. For the formation of these oxygenates, insertion of CO is necessary. Therefore, several authors and first of all M. E. Dry26 proposed a combined mechanism where hydrocarbons are mainly formed via CH2 insertion and oxygenates via CO insertion. We extend this proposal by the assumption that hydrocarbons are also formed via CO insertion in the same way as oxygenates. 

Heterolytic catalysis is promoted by W6+, Ti4+, Cr3+, V5+, and many Mo6+ complexes. These complexes do not normally react with peroxides. However, in the presence of electron-rich molecules, such as alkenes, amines, sulfides, etc., oxygen insertion in the reactant occurs. For example,... 

In an attempt to quantify the relationship between the TiOOH groups and the yield of propene oxide from the extinction coefficients of the latter s 1409-and 1493-cm-1 bands, it was determined that 0.6 mol of the epoxide formed per mole of framework Ti center in the molecular sieve. That is, at least 60% of all framework Ti (80% of the surface-exposed Ti) is converted to TiOOH upon reaction with H202. The consumption of the TiOOH species during the oxygen insertion into propene was also independently confirmed by the loss in intensity of its LMCT band at 360 nm when the catalyst was brought in contact with propene at room temperature (Fig. 50). 

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... 

The optoelectronic properties of the oxygen-inserted materials have also been measured.308 Compared to the parent ladder polysilanes, the absorption bands are blue shifted, as would be expected on insertion of a conjugation-inhibiting moiety. 

Scheme 2 Conversion of alcohol into cyclic acetal by anodic oxygen insertion.

Baeyer-Villiger oxidation of ketone 104 with metachloroperbenzoic (MCPBA) acid afforded lactone 105 (86 %). There was no detectable trace of the product resulting from oxygen insertion between centers C(2) and C(3). On treatment with acidic methanol, 105 was transformed into a 90 4 mixture of a- and p-acetal-acids 106 (94 %). Treatment with 2 equivalents of MeLi afforded methyl ketone 107... 

For the cw-dihydroxylation of protected lL-l,2 3,4-di-0-isopropylidenecyclohex-5-ene-l,2,3,4-tetrol (22g) to the diol lD-l,2 3,4-di-0-isopropylidene-a/to-inositol by RuClj/aq. Na(IO )/EtOAc-CH3CN/0°C cf. 3.1.2.1 and Fig. 3.3 [347]. Oxygen insertion by stoich. RuO /CCl occurred in addition to the secondary alcohol oxidation of the five-membered ring 5-0-benzoyl-l,2-0-isopropylidene-a-D-xylofnranose, giving the six-membered ring l,2-0-isopropylidene-6-0-benzoyl-3-oxa-a-D-e/7fftro -4-hexulopyranose-a-D-xylofuranose [325]. 

Despite the fact that a concerted oxygen insertion reaction appeared to be in complete agreement with existing experimental studies, Minisci and his group strongly advocated a... 

Intrinsic reaction coordinate following (IRC) analysis by both Bach and coworkers and Du and Houk ° showed that these TSs were connected to both reactant and product without the formation of a radical intermediate consistent with an oxygen insertion into the C—H bond (see inset). Shustov and Rauk ° advocated a bifurcation on the descent... 

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