Alkane from ketones

The yields of ketones, isolated from the reductive debromination of a-bromo-ketones by dicobalt octacarbonyl under basic phase-transfer conditions are good (Table 11.13), but are improved (>95%) by the use of stoichiometric amounts of the quaternary ammonium catalyst. Somewhat unexpectedly, in the case of the reductive dehalogenation of secondary benzylic halides, the yields of the coupled alkanes are... 

A very interesting synthetic method of bicyclo[n.l.O]alkanes from cychc ketones via this 1,3-C,H insertion of magnesium carbenoid as a key reaction was reported (equation 22) . 1-Chlorovinyl p-tolyl sulfoxide (76) was synthesized from cyclopentadecanone and chloromethyl p-tolyl sulfoxide in three steps in high overall yield. Lithium enolate of tert-butyl acetate was added to 76 to give the adduct 77 in quantitative yield. a-Chlorosulfoxide (77) in a toluene solution was treated with i-PrMgCl in ether at —78 °C and the reaction mixture was slowly warmed to 0°C to afford the bicyclo[13.1.0]hexadecane derivative 79 in 96% yield through the reaction of the intermediate magnesium carbenoid 78. 

The C atom on the carbonyl group is included in the count of C atoms when determining the alkane from which the ketone is derived. 

FIGURE 15.3. Distribution data between water and sodium dodecyl sulfate micelles as a function of the solute McGowan volume for the entire database (a) and for categorized classes of solutes (b), data from Reference 25. Database labels in (a) as in Figure 15.2. (A) hexadecane-water partition data for alkanes, from Reference 16. Labels in (b) ( ) alkyl benzenes (O) alkyl phenyl ketones (A) alkyl phenols ( ) halo benzenes and ( ) halo phenols. 

This is illustrated by the application of dioxiranes to polycyclic alkanes possessing a sufficiently rigid framework, such as the 2,4-didehydro adamantane case. For this substrate the reaction with DDO proceeds with 82% conversion during 12 h, yielding the expected 2,4-didehydroadamantan-7-ol, but also the precious 2,4-didehydroadamantan-lO-one in comparable yield (eq 35). The ketone derives from competitive dioxirane attack at the methylene positions a to the cyclopropyl moiety the latter is encompassed in the rigid 2,4-didehydroadamantane framework to lay constrained into a bisected orientation relative to the neighboring methylene C-H bonds. 

Conditions iron porphyrin (ImM) in a 1 1 alkanerbenzene mixture 90°C, PO2 10 bars, ol and one are used for the alcohol and ketone derived from the starting alkane. Yields are given in mol of product per mol of catalyst per 2h. For heptane, heptan-2,-3, and 4-ol and heptan-2,-3, and 4-one are formed. 

A method of almost universal applicability for the deoxygenation of carbonyl compounds is the Wolff-Kishner reduction While the earlier reductions were carried out in two steps on the derived hydrazone or semicarbazone derivatives, the Huang-Minlon modification is a single-pot operation. In this procedure, the carbonyl compound and hydrazine (hydrate or anhydrous) are heated (180-220 °C) in the presence of a base and a proton source. Sodium or potassium hydroxide, potassium-t-butoxide and other alkoxides are the frequently used bases and ethylene glycol or its oligomers are used as the solvent and proton source. Over the years, several modifications of this procedure have been used to cater to the specific needs of a given substrate. The Wolff-Kishner reaction works well with both aldehydes and ketones and remains the most routinely used procedure for the preparation of alkanes from carbonyl compounds (Table 9). This method is equally suitable for the synthesis of polycyclic and hindered alkanes. 

In a much less sophisticated system hydrocarbons are being oxidized by OH radicals at the cathode This occurs by simultaneous reduction of Fe(III) and oxygen at cpe. The OH radicals are generated by a Fenton reaction from Fe(II) and cathodically formed hydrogen peroxide. Linear alkanes from C5 to C o are being oxidized to ketones as the only products. The yields decrease with increasing number of carbon atoms and with the Fe(III) concentration. 

Otiier reductive eliminations that form C-H bonds do occur after initial dissociation of a ligand. For example, the elimination of carborane in Equation 8.14, - the elimination of ketone in Equation 8.15, and the elimination of aldehyde in Equation 8.16 aU occur after dissociation of a phosphine ligand. In contrast, die reductive elimination of alkane from the zirconocene alkyl hydride complex in Equation 8.17 occurs after association of ligand. ... 

Both alkanes and alcohols can be produced by the reduction of aldehydes and ketones. However, reactions that produce alcohols generally do not produce alkanes and vice versa. This means that the alcohols do not lie on the reductive pathway to alkanes. Of course, as noted in Chapter 8, alcohols produced by the reduction of aldehydes or ketones can be subsequently converted to alkanes, but the reductive methods for alkanes from the aldehydes and ketones are different from those for alcohols to alkanes. 

However, less is know about the quantitative details of these processes than is the case for the alkanes. In general, unimolecular decomposition of the alkoxy radicals [e.g., CH3CH20CH(0 )CH3 in the above reaction sequence] is more rapid than for an alkane-derived radical of similar structure. The major end product of ether oxidation is quite often an ester, the analog to the carbonyl compounds (aldehydes and ketones) generated from alkane oxidation. 

Cool Flames. An intriguing phenomenon known as "cool" flames or oscillations appears to be intimately associated with NTC relationships. A cool flame occurs in static systems at certain compositions of hydrocarbon and oxygen mixtures over certain ranges of temperature and pressure. After an induction period of a few minutes, a pale blue flame may propagate slowly outward from the center of the reaction vessel. Depending on conditions, several such flames may be seen in succession. As many as five have been reported for propane (75) and for methyl ethyl ketone (76) six have been reported for butane (77). As many as 10 cool flames have been reported for some alkanes (60). The relationships of cool flames to other VPO domains are depicted in Figure 6. 

Hydroperoxides have been obtained from the autoxidation of alkanes, aralkanes, alkenes, ketones, enols, hydrazones, aromatic amines, amides, ethers, acetals, alcohols, and organomineral compounds, eg, Grignard reagents (10,45). In autoxidations involving hydrazones, double-bond migration occurs with the formation of hydroperoxy—azo compounds via free-radical chain processes (10,59) (eq. 20). 

By-Products. Almost all commercial manufacture of pyridine compounds involves the concomitant manufacture of various side products. Liquid- and vapor-phase synthesis of pyridines from ammonia and aldehydes or ketones produces pyridine or an alkylated pyridine as a primary product, as well as isomeric aLkylpyridines and higher substituted aLkylpyridines, along with their isomers. Furthermore, self-condensation of aldehydes and ketones can produce substituted ben2enes. Condensation of ammonia with the aldehydes can produce certain alkyl or unsaturated nitrile side products. Lasdy, self-condensation of the aldehydes and ketones, perhaps with reduction, can lead to alkanes and alkenes. 

Synthesis of large ring alkanes and lactones from smaHer ring ketones via peroxides... 

Considerable interest arose during the 1970 s and 1980 s in the use of micro-organisms to produce useful fatty adds and related compounds from hydrocarbons derived from the petroleum industry. During this period, a large number of patents were granted in Europe, USA and Japan protecting processes leading to the production of alkanols, alkyl oxides, ketones, alkanoic adds, alkane dioic acids and surfactants from hydrocarbons. Many of these processes involved the use of bacteria and yeasts associated with hydrocarbon catabolism. 

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