Oxidation of methyl-substituted

Dutta TK, SA Selifonov, 1C Gunsalus (1998) Oxidation of methyl-substituted naphthalenes pathways in a versatile Sphingomomas paucimobilis strain. Appl Environ Microbiol 64 1884-1889. 

Oxidation of Methyl-Substituted Aromatics. Autoxidation of alkyl-substituted... 

Most studies of the metal-catalyzed oxidation of methyl-substituted arenes... 

According to this hypothesis, the results are modified from what would be expected from classical radical reactions. The interest in this hypothesis is that, with the sole exception of saturated hydrocarbons, it could apply to all the compounds that can be coordinated at the Tiiv center, such as alkenes, aromatics, alcohols, and sulfides. According to this hypothesis, the weak Lewis acidity of Tilv would help to bring the reactant into its coordination sphere. The initial coordination of the reactant would explain the oxidation of methyl-substituted aromatics in the aromatic ring and not in the side chain, even with a radical-type mechanism. 

Cabelli DE, Bielski BHJ, Seib PA (1984) A pulse radiolysis study of the oxidation of methyl substituted ascorbates. Radiat Phys Chem 23 419-429... 

Similarly, cobaltic and argentic ion have been generated by anodic oxidation of cobaltous and argentous ion, respectively, and used for the oxidation of methyl-substituted aromatic hydrocarbons to aldehydes 18a Electrogenerated mercuric ion can be used for the conversion of propene to acrolein 18al ... 

The kinetics of the oxidation of methyl substituted ethane-1,2-diols are generally similar to those observed for ethane-l,2-diol itself, with the exception of the oxidation of pinacol (see section 1.3.6). However, under certain conditions the rate of formation of the diester intermediate is comparable with its rate of decomposition to the reaction products, i.e. the ester is no longer in equilibrium with the reactants. The formation of the ester is buffer-catalysed (section 1.3.6) so equilibrium conditions are more likely to be attained when the reaction is carried out in a buffer. 

Photo-oxidation of amines remains a subject of interest. The photosensitized oxidation of methyl-substituted tertiary amines leads to NN-disubstituted formamides.150 The mechanism of this reaction has been studied, and Scheme 15 has been proposed.151 Charge-transfer complexation of amine with sensitizer,... 

The (/5/)-type dications were postulated as intermediates in the substitution of the CH3 group bonded with the benzene ring by an acetoxyl or acetamide group Y in the course of the ela trochemical oxidation of methyl-substituted derivatives of benzene in acetic acid and acetonitrile... 

Hydroxylation of monophenols to predominantely />-diphenols or oxidation of methyl-substituted aromatics by persulfates ... 

Oxidation of Methyl-substituted Cyclohexane. Methyltrioxorhenium is a versatile catalyst for the oxidative functionalization of cyclohexane derivatives with H2O2 as oxygen donor. Interestingly, there is a difference between the two stereoisomeric cis- and frans -configurations (eqs 47 and 48). ... 

Oxidation of methyl perfluoroalkyl sulphones with refluxing aqueous potassium permanganate produced the perfluorinated alkanesulphonic acid in 85% yield as the potassium salt (equation 86). On the other hand, attempted oxidation with sodium hypochlorite caused only chlorine substitution (equation 87). Reaction of the new sulphone with aqueous hydroxide gave the same perfluoroalkane sulphonic acid salt (equation 88). 

The oxidation of methyl fluoride to formaldehyde (Hyman et al. 1994), and of chloro-alkanes at carbon atoms substituted with a single chlorine atom to the corresponding aldehyde (Rasche et al. 1991). 

For the oxidations, the cathodic shifts (P— As- Sb- Bi) are nearly the same for the tetramethyl series and the octamethyl series. Since the shifts are independent of the degree of methyl substitution, these shifts can be used to estimate the 1/2 values for the series of unsubstituted diheteroferrocenes from the experimental value for l,l -diarsaferrocene. 

This work was extended to include the lead tetraacetate oxidation of methyl esters of meta- and para-substituted mandelic acids183,184 shown in equation 121. A kinetic study by Banerjee and collaborators showed the kinetic dependence on the ester concentration changed from second order in 1% (v/v) acetic acid in benzene to first order when the solvent contained more than 10% (v/v) acetic acid. These workers observed a significant decrease in AH (from 82.9 to 53.6 kcalmol-1) and in AS (from —5.84 to —35.6 e.u.) when the solvent composition was changed from 1% acetic acid to greater than or equal to 10% acetic acid in benzene. 

Inverse isotope effects such as those found in Table IV are associated with a change in hybridization at the site of deuterium substitutions (60). Hence, it is clear from these data that the transition state is symmetrical with respect to hydridization changes at both olefinic carbons when the reaction is carried out in aqueous solutions. However the last four entries in Table IV indicate that for the oxidation of methyl cinnamate in methylene chloride solutions only the iS-carbon has undergone a hybridization change (from sp ... 

These intrazeolite singlet oxygen ene reactions have synthetic potential because the cis effect observed in solution is suppressed in the zeolite [13]. Consequently, allylic hydroperoxides which are inaccessible by other routes may be available via this new technology. For example, photo-oxidations of aryl-substituted alkenes, 7, in sensitizer-doped NaY react to generate the allylic hydroperoxides as the major or exclusive product [17]. In contrast, in solution, the hydroperoxides are formed in only 5-20% yields, with 2-1-2 and 4-1-2 adducts dominating the reaction mixtures. In the case of 2-methyl-5-phenyl-2-hexene, 8, the regio-selectivity for 8b and 8c improved from 47% to 94% and the diastereoselectivity from 10% to 44% as the reaction is moved from solution into the zeolite [18] ... 

The isomer distribution obtained from the oxidation of mesitylene in acetic acid, sodium acetate depends on the anode material. Graphite strongly favours nuclear substitution to side chain substitution in the ratio 23 1 while at platinum this ratio is 4 1. Oxidation of methyl benzenes in acetic acid containing tetrabutykmmonium fluoroborate and no acetate ion gives benzyl acetate as the major product since loss of a proton from the radical-cation is now faster than nuclear substitution by acetic acid as the only nucleophile present [39]. 

The same group studied the lithium cation basicities of a series of compounds of the general formula R R R PO, i.e. phosphine oxides, phosphinates, phosphonates and phosphates, by using Fourier Transform Ion Cyclotron Resonance (FTTCR) mass spectrometry. A summary of their results is shown in Figure 4. The effect of methyl substitution on LCA as well as the correlation between LCA and PA was also investigated by Taft, Yanez and coworkers on a series of methyldiazoles with an FTICR mass spectrometer. They showed that methyl substituent effects on Li binding energies are practically additive. 

Oxidation of 5-substituted 2,3,3-trimethylisoxazolidines 553 with MCPBA afforded 6-substituted-3-hydroxytetra-hydro-l,3-oxazines 555 in high yields via the nitrone 554 intermediates formed by abstraction of hydrogen from the A -methyl group (Scheme 105) <1998T12959>. 

The oxidation of AT-substituted 5//-dibenz[6,/] azepines with MCPBA is complex and depends upon the nature of the N-substituent. AT-Acyl derivatives do not form the N-oxide but suffer epoxidation of the 10,11-bond. AT-Aryl derivatives undergo hydroxylation of the phenyl ring, whereas N-alkyl congeners, with the exception of the AT-methyl compound, yield mixtures of diphenylamines and acridones. The N-oxide is obtained from the A/-methyl derivative along with ring-opened and ring-contracted products (81CPB1221). 

---