Oxidation smooth

Another method for the hydrogenoiysis of aryl bromides and iodides is to use MeONa[696], The removal of chlorine and bromine from benzene rings is possible with MeOH under basic conditions by use of dippp as a ligand[697]. The reduction is explained by the formation of the phenylpalladium methoxide 812, which undergoes elimination of /i-hydrogen to form benzene, and MeOH is oxidized to formaldehyde. Based on this mechanistic consideration, reaction of alcohols with aryl halides has another application. For example, cyclohex-anol (813) is oxidized smoothly to cyclohexanone with bromobenzene under basic conditions[698]. 

Mn(III) is able to oxidize many organic substrates via the free radical mechanism [32], The free radical species, generated during oxidation smoothly initiate vinyl polymerization [33-35]. Mn(III) interacts also with polymeric substrates to form effective systems leading to the formation of free radicals. These radicals are able to initiate vinyl polymerization and, consequently, grafting in the presence of vinyl monomers. 

The A -(pyrrol-2-yl)carbamates 860 are oxidized smoothly by air to a mixture of the A -(5-hydroxy- 862 and 5-hydroperoxy- 863 -l,5-dihydro-2/7-pyrrol-2-yliden)carbamates (in 63% and 8% yield, respectively, when R = H, = Bn) (Scheme 166) <1997TL1293>. Oxidation with pure oxygen gives the same products in a yield of 47% and... 

Methyl ketones are oxidized smoothly by means of hypohalite in the haloform reaction (Sec. 16.11). Besides being commonly used to delect these ketones (Sec. 19.17), this reaction is often useful in synthesis, hypohalite having the special advantage of not attacking carbon-carbon double bonds. For example ... 

As mentioned in Sect. 4, Rh(II) acetate-propene oxide smoothly converts a-diazo phosphonoacetate to the a-ketone. However, replacement of the carboxy-... 

Reactions of another type involve cleavage of a carbon-carbon bond. Phenanthrene-quinone is oxidized smoothly to diphenic acid by hydrogen peroxide in warm acetic acid. Use of the reaction in structure elucidation is illustrated as follows. One of five disulfonic acids formed on sulfonation of phenanthrene was converted into the dimethoxyphenanthrene, which on oxidation afforded a dimethoxy-9,10-phenan-threnequinone. Oxidation of this quinone with HjOa-AcOH gave an acidic product... 

C. W. Smith investigated oxidations by hydrogen peroxide promoted by a purely catalytic amount of selenium dioxide. Acrolein is oxidized smoothly to monomeric acrylic acid with a 15% solution of hydrogen peroxide in t-butanol in the presence of 5 g. of selenium dioxide per mole of peroxide. Curiously, the same... 

The reaction (1.2) is catalyzed by nitrite oxidoreductase. This enzyme catalyzes actively the oxidation of nitrite at pH 8.0, while it catalyzes more preferentially the reduction of nitrate at pHs below 6.0. Therefore, the pH of the environments should be kept around 8 (Tanaka et al., 1983) for the bacterium to oxidize smoothly nitrite. 

Daum and Clarke6 report that ethylenethioketals can be oxidized smoothly with excess perphthalic acid to disulfones (3) and that the ketone function can be regenerated by decomposition under alkaline conditions in the presence of oxygen. This new protecting group is useful in cases where an acid-sensitive moiety has been introduced after protection of the ketone. Unfortunately the yields in the last step reported for two test cases were only 39% and 40%. 

C—H bond arylations of electron-deficient heteroarenes, such as azines, remain highly challenging. An elegant and versatile solution was recently elaborated, however, through a redistribution of electron density in the starting pyridine by chemical modification [77, 78]. It was found that pyridine N-oxides smoothly underwent regioselectively palladium-catalyzed direct arylations with a variety of aryl bromides (Scheme 9.36) [77a]. 

The particular value of the method is for converting methyl and polymethyl derivatives of polycyclic aromatic compounds into mono- and poly-carboxylic acids. For instance, 1-methylnaphthalene with a 42% excess of aqueous sodium dichromate solution in an autoclave at 240-250° gives 95% of 1-naphthoic acid in 18 h 2-methylnaphthalene with a 55% excess gives a 93% yield of 2-naphthoic acid the methyl group in fluoro-, bromo-, chloro-, nitro-, and methoxy-toluene as well as in xylenes and heterocycles can usually be oxidized smoothly to a carboxyl group. An excess of Na2Cr207 acts as a buffer and favors smooth reaction. With 1.5 moles of Na2Cr207 the reaction occurs in accord with the equation ... 

Results for the test Adler-Becker substrates, both precursors from our Wessely oxidation studies, are presented in Scheme 7. Interestingly, our first experiments revealed a dramatic difference in oxidation performance between acyclic and fused secondary benzylic alcohol substrates. While the acyclic substrate 30 afforded none of the epoxide quinone product 31, the fused pyran substrate 32 underwent oxidation smoothly to produce the desired epoxide product 32 in high yields. Encouraged by this excellent dearomatization... 

The supported Ru complex prepared by photoirradiation under Oj (K) was active for photooxidation of cycloalkanes to corresponding alcohols and ketones under O2. Cyclohexane oxidation smoothly proceeded without an induction period for at least 6 h, and the TON of the photooxidation reached 35 at 6 h with 96% selectivity. 

Aromatic and aliphatic aldehydes are oxidized smoothly by bromine in aqueous solution [101]. The reaction can also be performed in alcohol as the solvent, but in this case, the corresponding esters are formed in good yields [102,103]. Iodine in the presence of alkali is also effective for this transformation [103]. 

Copper(I)-catalyzed intramolecular [2 + 2]-photocycloaddition of diallyl ethers and homoallyl vinyl ethers provides a new route to 3-oxabicyclo- and 2-oxabicyclo[3.2.0]heptanes, respectively.Different structural variants of diallyl ethers have been investigated. UV irradiation of diaUyl ethers 77a-f in the presence of CuOTf catalyst produces 3-oxabicyclo[3.2.0]heptanes 78a-f in moderate to excellent yields (Scheme 22). The diallyl ethers 77c and 77d having alkyl substitution at the aUyhc position produce exclusively the 2-exo-alkyl-3-oxabicyclo [3.2.0] heptanes 78c and 78d, respectively. The observed stereoselectivity arises through photocycloaddition of the Cu(l)-diene complex 80, which is stericaUy less crowded than the complex 81 with an axial alkyl group. The bicychc ethers 78 can be oxidized smoothly to the lactones 79 with RuO. Cu(l)-catalyzed photocycloaddition of homoallyl vinyl ethers 82 also proceeds smoothly, producing 2-oxabicyclo[3.2.0]heptanes 83 (Scheme 22). 

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