Benzyl oxidation

Alkyl groups attached to aromatic rings are oxidized more readily than the ring in alkaline media. Complete oxidation to benzoic acids usually occurs with nonspecific oxidants such as KMnO, but activated tertiary carbon atoms can be oxidized to the corresponding alcohols (R. Stewart, 1965 D. Arndt, 1975). With mercury(ll) acetate, allyiic and benzylic oxidations are aJso possible. It is most widely used in the mild dehydrogenation of tertiary amines to give, enamines or heteroarenes (M. Shamma, 1970 H. Arzoumanian. 1971 A. Friedrich, 1975). 

Salts composed of an anion, RO—, and a cation, usually a metal, can be named by citing first the cation and then the RO anion (with its ending changed to -yl oxide), e.g., sodium benzyl oxide for CgH5CH20Na. However, when the radical has an abbreviated name, such as methoxy, the ending -oxy is changed to -oxide. For example, CHjONa is named sodium methoxide (not sodium methylate). 

Allylic and benzylic oxidation. PCC in refluxing CH2C12 can oxidize allylic2 and benzylic23 methylene groups to keto groups in satisfactory yield. 

FIGURE 4.46 Stereochemistry of the cytochrome P450-catalyzed benzylic oxidation of (R)-ethylbenzene-1 -d. 

Dorn et al. have studied the fate of epifenonane in polluted water (24). When Glatt River water was fortified with epifenonane at 10 ppm and exposed to open air for four weeks, 61% of the applied dose was recovered as intact epifenonane. Volatility losses amounted to 18% of the applied 3H while metabolites contributed a mere 21%. The characterized metabolites are listed in Table VI. The two major degradation routes involved epoxide modification and benzylic oxidation. 

Asymmetric allylic oxidation and benzylic oxidation (Kharasch-PSosnovsky reaction) are important synthetic strategies for constructing chiral C—O bonds via C—H bond activation.In the mid-1990s, the asymmetric Kharasch-Sosnovsky reaction was first studied by using chiral C2-symmetric bis(oxazoline)s. " Later various chiral ligands, based mainly on oxazoline derivatives and proline derivatives, were used in such asymmetric oxidation. Although many efforts have been made to improve the enantioselective Kharasch-Sosnovsky oxidation reaction, most cases suffered from low to moderate enantioselectivities or low reactivities. 

Sheldon and coworkers have developed chromium-substituted molecular sieves (CrAPO-5) as recyclable solid catalysts for several selective oxidations, among them also the allylic" and benzylic ° " ° " ° oxidations using TBHP or O2 as the terminal oxidants (equation 63), which yielded the corresponding benzylic ketones in moderate yield (conv. 13-70%) and moderate to good selectivity (41%, 65-97%). The benzylic alcohols were formed as side products. Allylic oxidation also proceeded with good conversions, while selectivities were lower and both possible products, the allylic ketone (31-77% selectivity) and the allylic alcohol (0-47% selectivity), were formed. Chromium sUicalite showed activity for selective benzylic oxidation in the presence of TBHP as well as giving mainly the allylic ketone (2-cyclohexen-l-one with 74% selectivity) and the allylic alcohol as minor product (2-cyclohexen-l-ol with 26% selectivity) -. ... 

Keratinocytes, cosmetics, 613 a-Ketoalkyl radicals, 252 y-Ketoalkyl radicals, 252 of-Keto esters, benzylic oxidation, 518 2-Ketoglutarate, hydrogen peroxide determination, 655... 

Abstract The purpose of this chapter is to present a survey of the organometallic chemistry and catalysis of rhodium and iridium related to the oxidation of organic substrates that has been developed over the last 5 years, placing special emphasis on reactions or processes involving environmentally friendly oxidants. Iridium-based catalysts appear to be promising candidates for the oxidation of alcohols to aldehydes/ketones as products or as intermediates for heterocyclic compounds or domino reactions. Rhodium complexes seem to be more appropriate for the oxygenation of alkenes. In addition to catalytic allylic and benzylic oxidation of alkenes, recent advances in vinylic oxygenations have been focused on stoichiometric reactions. This review offers an overview of these reactions... 

This system also catalyzes the benzylic oxidation of 1,2,3,4-tetrahydro-naphthalene [35] (Eq. 6) and hydrocarbons containing benzyl groups with... 

SCHEME 131. Copper(II)-catalyzed benzylic oxidation and oxidation of cyclohexane with 30%... 

All nuclear nucleophilic substitutions on derivatives of compound 4 have involved the replacement of a substituent at position 7 (the equivalent of the y -position in pyridine). In the 7-chloro derivative 244, replacement is possible by methoxide ion,151 by ammonia (with some rearrangement)192 and by amines,151 and by thiourea to give the sulfide (245).151 Substituted 7-chloro derivatives undergo replacement by benzyl oxide ion to give a 7-benzyloxy derivative155,220 and by azide,153 hydrazine,216 hydrosulfide (to give the 7-thione166), and methyl thiolate.220 Some of these compounds carry D-ribofuranosyl benzoate substituents on N-2 or N-3, and methoxide ion... 

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