Decalin, 2-methyl

In addition to the ahphatic (chain) molecules, the saturates contain cycloalkanes, called naphthenes, having mainly five or six carbons in the ring (Fig. 5). Methyl derivatives of cyclopentane and cyclohexane ate commonly found in greater quantity than the parent unsubstituted stmctures and can be present at levels above 2% (2). Fused-ting dicycloalkanes such as decahydronaphthalenes (decalins) and hexahydroindans are also common, but nonfused bicyhc naphthenes, eg, cyclohexyl cyclohexane, are not. 

There are probably several factors which contribute to determining the endo exo ratio in any specific case. These include steric effects, dipole-dipole interactions, and London dispersion forces. MO interpretations emphasize secondary orbital interactions between the It orbitals on the dienophile substituent(s) and the developing 7t bond between C-2 and C-3 of the diene. There are quite a few exceptions to the Alder rule, and in most cases the preference for the endo isomer is relatively modest. For example, whereas cyclopentadiene reacts with methyl acrylate in decalin solution to give mainly the endo adduct (75%), the ratio is solvent-sensitive and ranges up to 90% endo in methanol. When a methyl substituent is added to the dienophile (methyl methacrylate), the exo product predominates. ... 

To a solution of 50 grams of 6,7-dimethoxy-3-methyl-T(4 -ethoxy-3 -methoxybenzyl)-dihy-droisoquinoline base in 200 ml of dry benzene are added 150 ml of decalin, and the mixture is distilled until its temperature reaches 180°C. 1.5 grams of 5% palladium on carbon are then added. The mixture is stirred under reflux for about 6 hours to dehydrogenate the dihydroisoquinoline. On cooling, the reaction mixture is diluted with petroleum ether and the precipitated 6,7-dimethoxy-3-methyl-1-(3 -methoxy-4 -ethoxybenzyl)-isoquinoline is filtered off and recrystallized from dilute ethanol. 

Thus, treatment of 28 with H2 (69 bar) for 20 hours at 100°C in decalin gave diphenylmethane (41%) together with small amounts of tetraphen-ylethene and tetraphenylethane. With 29, under somewhat milder conditions (H2, 1.8 bar, 140°C for 5 hours), a 92% yield of benzyl methyl ether was obtained. 

In an approach by Jung and Nishimura, the assembly of the dysidiolide decalin skeleton 54 was deemed possible via an intermolecular Diels-Alder reaction between cydohexene 52 and dienophile 53 [14]. Based on precedent established by Wulff et al. [15] [where Z = C(OCH3)=Cr(CO)5], the cycloaddition should give predominantly the exo isomer as shown (Scheme 19.12). However, all attempts to effect the cydoad-dition simply gave recovery of starting material. It was reasoned that steric hindrance was to blame. The steric hindrance assodated with the dienophile was decreased by replacing one of the methyl groups with another double bond in the... 

Dimethyl methyithio(phenylamino)methylenemalonate was cyclized in boiling decalin for 2 hr to afford methyl 2-methylthio-4-hydroxyquinoline-3-carboxylate in 70% yield (69T4649). 

Therefore, nine steps or synthetic operations are necessary in the conessine synthesis for isomerising the cir-B/C decalin system to trans-hIC, a transformation that in the cortisone synthesis is accomplished without any extra step, since it takes place spontaneously in the oxidation step, which, in turn, is necessary to introduce the second angular methyl group and build up ring D of cortisone in a stereoselective manner. Better correlation amongst different synthetic operations would be difficult to find in more recent synthesis of similar complexity and magnitude than that of Sarett. 

With this idea in mind, the retrosynthetic analysis (Scheme 13.2.8) leads now to unsaturated cw-decalin 28 which could be reduced to 5-methyl-2-cyclohexenone 31. In the synthetic direction there was initially the uncertainty of whether nitrone 27 would cyclise to 26b rather than to the desired adduct 26a (see below Scheme 13.2.9). However, the authors felt that in fact the risk was "less critical in view of the regioselectivity observed in intramolecular N-alkenylazomethinimine additions involving non-polarised olefinic bonds" [11][12]. 

The solvents most commonly employed are water, ethyl and methyl alcohol, ether, benzene, petroleum ether, acetone, glacial acetic acid also two or three solvents may be mixed to get the desired effect as described later. If you still cannot dissolve the compound, try some of these chloroform, carbon disulfide, carbon tetrachloride, ethyl acetate, pyridine, hydrochloric acid, sulfuric acid (acids are usually diluted first), nitrobenzene, aniline, phenol, dioxan, ethylene dichloride, di, tri, tetrachloroethylene, tetrachloroethane, dichloroethyl ether, cyclohexane, cyclohexanol, tetralin, decalin, triacetin, ethylene glycol and its esters and ethers, butyl alcohol, diacetone alcohol, ethyl lactate, isopropyl ether, etc. 

The thermal cyclization of 3-(l,3-butadienyl)indoles 692 in refluxing cis-decalin afforded the carbazoles 698. Selective hydrolysis of the 3-carbonate ester, methylation of the corresponding 3-hydroxycarbazoles 699 with methyl iodide in the presence of... 

Bhattacharyya et al. reported the first total synthesis of clausenalene (90) to establish its structure (99). This total synthesis uses Japp-Klingemann and Fischer-Borsche reactions as key steps. The phenyl hydrazone 1000 required for the transformation to 1-0x0-tetrahydrocarbazole 1001 under Fischer-Borsche conditions was obtained by condensation of 2-hydroxymethylene-5-methylcyclohexanone (999) with diazotized 3,4-methylenedioxyaniline (998) using Japp-Klingemann conditions. Wolff-Kishner reduction of 1001 furnished 3-methyl-6,7-methylenedioxy-l,2,3,4-tetrahydrocarbazole (1002), which, on aromatization wifh 10% Pd/C in decalin, afforded clausenalene (90) (99) (Scheme 5.143). 

The validity of Eq. (6.1) has been carefully established for linear and branched paraffins, cyclohexane and methylated cyclohexanes, including molecules consisting of several cyclohexane rings in the chair conformation (e.g., cis- and frani-decalin, bicyclo[3.3.1]nonane, adamantane, and methylated adamantanes) as well as in boat conformation (e.g., iceane and bicyclo[2.2.2]octane) [44]. No special effect seems to contribute to the chemical shift because of the presence of cyclic stmctures. 

The latter are, indeed, of considerable interest. They have a long history in conformational chemistry [258,259] and deserve attention for the major role they play in the discussion and prediction of stmcmral feamres. Typically, we refer here to gauche interactions exemplified by one of the methyl protons of the axial methylcyclohexane (for instance) interacting with the axial protons at C-3 and C-5 of the ring, or to the three gauche interactions occurring in cw-decalin. ... 

The three solid phase tetralin and decalin hydroperoxides have enthalpies of reaction that are surprisingly comparable, —93.9 6.4 kJmoR, despite the sometimes large error bars associated with either the peroxide or corresponding alcohol and their differences in structure. Notably, the gas phase reaction enthalpy for the cumyl hydroperoxide is nearly identical to the solid phase reaction enthalpy for the 1-methyl-1-tetralin hydroperoxide, —87.0kJmoR, for these structurally similar compounds and supports the hypothesis that the gas and condensed phase formal reaction enthalpies are nearly the same for all compounds. Flowever, for 2,5-dimethylhexane-2,5-dihydroperoxide, the enthalpies of reaction 5 per hydroperoxy group for the solid and gaseous phase are not close —57 and —76 kJmoR, respectively. Compare them with the enthalpies of reaction for ferf-butyl hydroperoxide of —66 (Iq) and —67 or —78 (g) kJmoR. For the unsaturated counterpart, 2,5-dimethylhex-3-yne-2,5-dihydroperoxide, the solid and gas phase enthalpies of reaction per hydroperoxy group are —64.2 kJmoR and —74.6 kJmoR, respectively. 

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