Ketone epoxidation

There are many ways to categorize the oxidation of double bonds as they undergo a myriad of oxidative transformations leading to many product types including epoxides, ketones, diols, endoperoxides, ozonides, allylic alcohols and many others. Rather than review the oxidation of dienes by substrate type or product obtained, we have chosen to classify the oxidation reactions of dienes and polyenes by the oxidation reagent or system used, since each have a common reactivity profile. Thus, similar reactions with each specific oxidant can be carried out on a variety of substrates and can be easily compared. 

The epoxide-ketone rearrangement is not limited to polyfluorooxiranes. Michel and Schlosser have studied the isomerization of 2-fluorooxiranes to oc-fluoro ketones by the action of triethylamine trishydrofluoride.47 Thus, 2-substituted 2-fluorooxiranes 10 isomerize re-giosclectively to fluoromethyl ketones 11 when heated at 125 C. 

The oxo species further reacted with olefins to form the corresponding epoxides, ketones, and alcohols (256). 

Because the petrochemical industry is based on hydrocarbons, especially alkenes, the selective oxidation of hydrocarbons to produce organic oxygenates occupies about 20% of total sales of current chemical industries. This is the second largest market after polymerization, which occupies about a 45% share. Selectively oxidized products, such as epoxides, ketones, aldehydes, alcohols and acids, are widely used to produce plastics, detergents, paints, cosmetics, and so on. Since it was found that supported Au catalysts can effectively catalyze gas-phase propylene epoxidation [121], the catalytic performance of Au catalysts in various selective oxidation reactions has been investigated extensively. In this section we focus mainly on the gas-phase selective oxidation of organic compounds. 

During our further studies of ketone catalysts, ketone 16 was found to be highly enantioselective for a number of acyclic and cyclic d.s-olefins (Table 10.6).73-74 It is important to note that the epoxidation is stereospecific with no isomerization observed in the epoxidation of acyclic systems. Ketone 16 also provides encouragingly high ee s for certain terminal olefins, particularly styrenes.74-75 In general, ketones 1 and 16 have complementary substrate scopes. In our subsequent study of the conformational and electronic effects of ketone catalysts on epoxidation, ketone 17, a carbocyclic analog of 16, was found to be highly enantioselective for various styrenes (Table 10.7).76... 

Table 18.4 Polyene hydrocarbons, epoxides, ketones, and related compounds known or suspected as sex pheromones for lymantriid moths. Because of the uncertainty of subfamilies in the Lymantriidae, species have simply been listed alphabetically. Compounds in bold have been found in pheromone gland extracts or aeration extracts and have been shown to be active in behavioral bioassays or field trials, compounds in normal font have been found in pheromone gland or aeration extracts, compounds in italics have been shown to attract males infield screening trials, and underlined compounds have been shown to be antagonistic.

Within the Lymantriidae, patterns of pheromone use are not yet clear, and there appears to be the greatest diversity of pheromone structures. Roughly two-thirds of the approximately thirty species for which pheromones or sex attractants have been reported have polyenes, epoxides, ketones, or polyunsaturated esters that could be classified as belonging to the Type n class, whereas the remainder use branched-chain epoxyalkane pheromones. Remarkably, even within a genus (e.g., Lymantria or Euproctis), congeners produce pheromones of different classes (Table 18.4). 

There is one more aspect of the problem under consideration. Cholesterol autoxidized on the air with formation epoxides, ketones, hydroperoxy- and hydroxy-derivatives [26] (Figure 9). 

The selenium-stabilized carbanions derived by deprotonation of selenoacetals by strong bases, such as a mixture of KDA-lithium r-butoxide, LiTMP in HMPT/THF or LBDA in THF at -78 °C, react readily with a variety of electrophiles including primary or secondary halides, epoxides, ketones, aldehydes and enones, followed by deprotection, to give ketones, 3-hydroxy ketones, a-hydroxy ketones and 1,4-dicarbonyl compounds respectively. - - ... 

Other electrophiles include H, RX, RCOX, epoxides, ketones, aldehydes, etc... 

Lithium amides derived from secondary amines like lithium diisopro-pylamide (1) appear to be strong enough bases to deprotonate epoxides, ketones, etc. However, when 1, which is a non-chiral base, deprotonates the non-chiral epoxide cyclohexene oxide (2), equal amounts of the two enantiomeric products (5)- and (/ )-cyclohex-2-enol (3) are formed in the abstraction of a proton from carbon 2 and 5, respectively, with accompanying opening of the epoxide ring (Scheme 1). Thus, none of the two enantiomeric products is formed in enantiomeric excess (ee), i.e., the reaction shows no stereoselectivity (Scheme 1). 

The observed selectivity is 3°>2°>1° as expected for a homolytic pathway and species with 4 °-4 ° C—C bonds are very efficiently assembled, especially in the presence of H2 which increases the selectivity because H atoms which are formed are somewhat more selective for the weakest C—H bonds in the molecule. H atoms are also very tolerant of functional groups, so a variety of functionalized molecules (esters, epoxides, ketones etc.) can also be dehydrodimerized. Methylcyclohexane only gives 12% of the 4°-4° dehydrodimer in the absence of H2, but in its presence enough of this dimer is formed to allow it to crystallize from the product mixture (equation 44). Alkanes can also be functionalized by cross-dimerization with other species. Equation 45 shows the results from cyclohexane and methanol. The three products are formed in approximately statistical amounts. The polarities of the three species are so different that the glycol can be removed with water and the bicyclohexyl separated by elution with pentane. 

Peroxy acids are useful oxidizing agents and are generally analysed on the basis of their ability to oxidize iodide ion to iodine which can be determined titrimetrically or colorimetrically. They also oxidize alkenes to epoxides, ketones to esters or lactones, thioethers to sulphoxides and sulphones, and tertiary amines to amine oxides. 

This ready access to 77 -arene ruthenium(O) complexes has allowed the entry to other functionalized derivatives. Thus, electrophilic substitution reactions have been performed starting from [Ru(77" -GOD)(r7 -haloarene)] via sequential addition of LiBu and a suitable electrophile at low temperature. A wide range of electrophiles such as acyl chlorides, chloroformates, chlorophosphines, epoxides, ketones, 7-lactones, etc., have been involved in this transformation. As an example, lithiation of [Ru(77" -GOD)(77 -l,2-MeG6H4Br)] and further reaction with... 

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