Electrophilic attack, permanganate oxidations

Whereas the Cyt P-450 mechanism resembles the chemical oxidation by hyper-valent transition metal oxidants through an electrophilic attack (nature s permanganate), the FAD-dependent mechanism parallels the oxidation of organic compounds by peroxides or peracids, which act as nucleophiles (nature s m-chloro-... 

Oxidation of methyl( )-cinnamate with quarternary ammonium permanganates in CH2Cl2 is fastest for the ions which minimize the interionic distance in the quarternary ammonium ion pair. An inverse secondary deuteriom isotope effect was observed. The reaction is initiated by an electrophilic attack, followed by a slower conversion of a 7r-complex to a cyclic manganate(V) diester (2). 

TL5981>. The proposed mechanism involves the oxidation of the amine to an imine, tautomerization to an enamine, and a sequence of nucleophilic attacks on the pyridazine rings followed by oxidation steps. The oxidant of choice is (bispyridine)silver permanganate <1982TL1847>, which is easily prepared, mild in action, and is soluble in organic media. If R1 = H in the product 77, electrophilic substitution (e.g., bromination, nitration, Mannich, and Vilsmeier-Haack-Arnold reactions) occurs at this position. 

The surmised mechanism is shown in Figure 14.27. It is assumed that the enolate, not the ketone itself, reacts with the permanganate. The Mn04 anion presumably attacks the enolate carbon electrophilically with one of its doubly bonded O atoms. The manganese(V) acid mowoester C is formed and is oxidized by a permanganate ion to... 

In this section, permanganate [principally potassium permanganate (KMnOq)] will be used to oxidize alkenes to 1,2-diols. It is apparent from preceding discussions that alkenes can donate an electron pair to an electrophilic center. The structure of permanganate (MnOq", 239) is best viewed as the 1,3-dipolar molecule (b O and an negative O). Reaction occurs between an alkene, which donates electrons to the electrophilic oxygen of the dipole. As the Jt-bond breaks, positive character develops on one carbon, which is attacked by... 

Kutney et al. ° have investigated the general reactivity of the various positions in the vindoline (205) nucleus, and have prepared several new derivatives. Electrophilic substitution occurs with particular facility at position 10, as expected Nb can be protected as the 3-lactam by oxidation with mercuric acetate, preferably on vindoline O-acetate. In contrast, dihydrovindoline derivatives are oxidised at position 5. Potassium permanganate was observed to attack both positions 3 and 5, with concomitant oxidation of the iVa-methyl group. Substitution reactions in ring C, particularly at C-17, depend critically on the existing substitution, and on the conformation of ring c. 

Due to the electrophilic nature of osmium tetroxide, electron-withdrawing groups connected to the alkene double bond retard the dihydroxylation. This is in contrast to the oxidation of alkenes by Potassium Permanganate, which preferentially attacks electron-deficient double bonds. However, in the presence of a tertiary amine such as pyridine, even the most electron-deficient alkenes can be osmylated by osmium tetroxide (eq 4). The more highly substituted double bonds are preferentially oxidized (eq 5). 

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