Dimethylcyclohexanes oxidation

Other methods for the preparation of cyclohexanecarboxaldehyde include the catalytic hydrogenation of 3-cyclohexene-1-carboxaldehyde, available from the Diels-Alder reaction of butadiene and acrolein, the reduction of cyclohexanecarbonyl chloride by lithium tri-tcrt-butoxy-aluminum hydride,the reduction of iV,A -dimethylcyclohexane-carboxamide with lithium diethoxyaluminum hydride, and the oxidation of the methane-sulfonate of cyclohexylmethanol with dimethyl sulfoxide. The hydrolysis, with simultaneous decarboxylation and rearrangement, of glycidic esters derived from cyclohexanone gives cyclohexanecarboxaldehyde. 

This dry ozonation procedure is a general method for hydrox-ylation of tertiary carbon atoms in saturated compounds (Table 1). The substitution reaction occurs with predominant retention of configuration. Thus cis-decalin gives the cis-l-decalol, whereas cis- and frans-l,4-dimethylcyclohexane afford cis- and trans-1,4-dimethylcyclohexanol, respectively. The amount of epimeric alcohol formed in these ozonation reactions is usually less than 1%. The tertiary alcohols may be further oxidized to diols by repeating the ozonation however, the yields in these reactions are poorer. For instance, 1-adamantanol is oxidized to 1,3-adamantane-diol in 43% yield. Secondary alcohols are converted to the corresponding ketone. This method has been employed for the hydroxylation of tertiary positions in saturated acetates and bromides. 

Amines, thiols, eOH (p. 226), etc., will also add to the 0-carbon atom of 0-unsaturated carbonyl compounds and esters, but the most important reactions of C=C—C=0 systems are in Michael reactions with carbanions reactions in which carbon-carbon bonds are formed. A good example is the synthesis of l,l-dimethylcyclohexan-3,5-dione (dimedone, 100) starting from 2-methylpent-2-ene-4-one (mesityl oxide, 101) and the carbanion 0CH(CO2Et)2 ... 

In regard to the stereoselectivity of the insertion process, Murray and coworkers have shown that the CH oxidation of substituted cyclohexanes by dioxiranes is, like the already discussed epoxidation, highly stereo-controUed . A specific case is c -decalin, which gives only the cis alcohol, as exemplarily displayed in equation 27. A similar stereoselective retention of configuration was also obtained for frawi-decalin and cis- and frawi-dimethylcyclohexanes"°. In fact, complete retention of configuration was demonstrated in the CH oxidation of chiral alkanes ". For example, the optically active (f )-2-phenylbutane was converted by either DMD or TFD" to (5 )-2-phenylbutan-2-ol (equation 28) without any loss of the enantiomeric purity (ep) in the product. 

Ammoxidation is also used for the manufacture of isophthalonitrile from m-xylene. The catalysts claimed in the patents are mixed oxides, e.g., of Mo, V, and Sb. The dinitrile is hydrogenated to m-xylylene diamine and m-diamino-dimethylcyclohexane, used for the production of the corresponding diisocyanates that are less toxic than toluene diisocyanate TDL A different use is for the production of tetrachloroisophthalonitrile, a potent fungicide. 

Oxidation of fluorinated alkenes with oxygen is possible. The reaction of hexafluoropropene and perfluorohept-l-ene in a solution of perfluoro(dimethylcyclohexane) has been described.4 The reaction is carried out with air in a steel autoclave at 200"C and gives perfluorocarbonyl fluoride. 

Draw the three-dimensional structures of the following, indicating the interactions that may exist (a) -butane in its staggered form (b) -butane in its eclipsed form about the 2,3-bond (c) 1,2-dibromoethane in its most stable form (d) cyclopropane (e) 1,2-epoxyethane (ethylene oxide) showing the lone pairs of electrons on the oxygen (f) cis- and rart.v-1,4-dimethylcyclohexane in the chair form (g) /ran.v-cyclohexane-l,2-dicarboxylic acid (h) cyclohexene. 

Dimedon, 5,5-dimethylcyclohexane-l,3-dione, is prepared by an interesting process discovered by Vorlander. The reaction of 1 mole each of diethyl malonate, mesityl oxide, and sodium ethoxide in absolute ethanol probably involves a Michael addition followed by an intramolecular ester condensation to close the ring to give the diketo ester formulated (procedure of Shriner and Todd. Aqueous potassium... 

In a similar manner, 1,7-octadiene and 1,6-heptadiene can be reductively cyclized to give, after acidic workup of the resulting carbometalation product (see Section 1.5.8.4.4,), cisjtrans mixtures of 1,2-dimethylcyclohexane and 1,2-dimethylcyclopentane, respectively, with opposite preference of the diastereomersls. The reaction uses 1.5-fold equimolar amounts of dibutyl-magnesium and is catalyzed by dicyclopentadienylzirconium dichloride. If oxidative workup is used instead of hydrolysis, the corresponding diols are obtained15. Several other examples of this type have been reported82. 

The stereospecificity of the hydrocarbon ozonation was investigated by measuring the isomer distribution of tertiary alcohols formed on ozonating cis- and fmri5-l,2-dimethylcyclohexane and cis- and trans-DecR-lin. Other oxidation products are formed in these ozonations, but the tertiary alcohols are easily separated from these by gas chromatography. Some results are shown in Table II. The observed isomer distributions of tertiary alcohols are independent of time for up to 3 hours ozonation... 

Fe(opba)]20 catalyzes the oxidation of cyclohexane and adamantane with total yields up to 5 % based on the oxidant after 24 h with a ratio A/K of 0.9 and a ratio 3°/2° of 3 (84). These results are in line with a mechanism involving hydroxyl radicals as transient intermediates. In the oxidation of cyclohexane catalyzed by [Fe(tpca)(H20]20 (C104)2, the average alcohol-to-ketone ratio is equal to 7, which is much higher than the value characteristic of radical chain oxidation (54). Also, the stereospecificity observed in the oxidation of cis- and trans-l,2-dimethylcyclohexane (up to 97% retention of configuration) points toward the involvement of a metal-based oxidant (83). A few other complexes showing low to moderate catalytic activity in the oxidation of cyclohexane and/or adamantane are listed in Table IV. 

The hydrogenation of substituted cyclic alkenes is anomalous in many cases in that substantial amounts of rran -addition products are formed, particularly with palladium catalysts. For example, the alkene 19 on hydrogenation over palladium in acetic acid gives mainly frans-decalin (7.12), and the alkene 1,2-dimethylcyclohexene 20 gives variable mixtures of cis- and trans-, 2-dimethylcyclohexane depending on the conditions (7.13). Similarly, in the hydrogenation of the isomeric dimethylbenzenes (xylenes) over platinum oxide, the cis-dimethylcyclohexanes are the main products, but some trans isomer is always produced. 

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