Ketones remote oxidation

Tab. 4 Remote oxidation of ketones in acetonitrile/lithium perchlorate...

On the other hand, acyclic ketones, when oxidized in trifluoroacetic acid [82] or in MeCN [83], gave dehydrogenated ketones and products substituted at the remote (y, S, or e) positions. 

Remote oxidation of ketones 9-34 Dimerization of silyl enol ethers or of lithium enolates... 

Remote oxidation. The major products of oxidation of (-)-bornyl acetate (1) with CrOa are the Cs- and Ct-ketones, 2 and 3. Preferential hydroxylation of 1 at Cs is also observed with microorganisms. The correspondence in regioselectivity probably is a result of greater accessibility of the Cs-position. ... 

A hydroxybomeol (angelicoidienol, 790) was isolated from Pleurospermum angelicoidesf it was identical with the diol synthesized by Money et al. in 1979 by remote oxidation of bomyl acetate (348) with chromic oxide in acetic anhydride and acetic acid this yielded 40% of the ketone 791, metal hydride reduction of which gave the diol 790. ... 

Several ketones can undergo remote oxidative cyanation to give y-cyano-ketones (Scheme 149) 322 the reaction is believed to... 

Remote oxidation of estrone. Reaction of estrone (1) with this thallium(III) salt gives as the major products 2 and 3. The p-quinol 3 had been obtained earlier by oxidation of 1 with thallium(III) trifluoroacetate (4, 500-501). The ketone 2 is not formed via 3, which is stable to the oxidant, but it can be formed by oxidation of 9,11-dehydroestrone in the same way. ... 

Due to the retractive forces in stretched mbber, the aldehyde and zwitterion fragments are separated at the molecular-relaxation rate. Therefore, the ozonides and peroxides form at sites remote from the initial cleavage, and underlying mbber chains are exposed to ozone. These unstable ozonides and polymeric peroxides cleave to a variety of oxygenated products, such as acids, esters, ketones, and aldehydes, and also expose new mbber chains to the effects of ozone. The net result is that when mbber chains are cleaved, they retract in the direction of the stress and expose underlying unsaturation. Continuation of this process results in the formation of the characteristic ozone cracks. It should be noted that in the case of butadiene mbbers a small amount of cross-linking occurs during ozonation. This is considered to be due to the reaction between the biradical of the carbonyl oxide and the double bonds of the butadiene mbber [47]. 

For the anodic substitution of unactivated CH-bonds, some fairly selective reactions for tertiary CH-bonds in hydrocarbons and y—CH-bonds in esters or ketones are available [85-87]. However, in some cases, a better control of follow-up oxidations remains to be developed. Chemically, a number of selective reactions are available, such as the ozone on silica gel for tertiary CH-bonds [88], the Barton or Hoffmann-LoefHer-Freytag reaction for y-CH-bonds [89], and for remote CH-bonds, Cprop)2NCl/H [90, 91], photochlorination of fatty acids adsorbed on alumina [92] or template-directed oxidations [93]. 

Oxidation of Remote CH Bonds in Ketones, Carboxylic Acids, and... 

With ketones, a remote regioselective acetamidation is found. This result is mechanistically in accordance with the oxidation of the oxygen atom of the carbonyl group to a radical cation that abstracts a hydrogen from a remote CH bond. The generated radical is then oxidized to a cation, that reacts with acetonitrile to get the acetamide (Fig. 3) [15],... 

The carboxidation of internal 2-butene and 2-pentene proceeds with a much smaller cleavage (8%), yielding the ketones as major products. The reason for this difference in the behavior of terminal and internal alkenes is unclear. One may relate it to dissipation of the energy evolved at the oxidative attack to the double bond. The efficiency of this process maybe higher for the more remote position of the double bond from the end of the molecule. However, the cleavage contribution for the ethylene is as low (7%) as that for the internal alkenes, which undermines the idea. 

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