2-Methyldecalin

Similarly, androstane-5a,6a,17)S-triol 6-tosylate 17-benzoate (115b) is converted to 17)S-hydroxy-6)S-methyl-10(5 6)SH)flZ)en-androstan-5-one benzoate (116b) on treatment with calcium carbonate in dimethylformamide. Similar treatment of 10-methyldecalin-l,9-diol 1-tosylate (121) gives 10-methylbicyclo[5.3.0]decan-l-one (122). 

An increment system has been derived for methyldecalins [230] and methylated perhy-drophenanthrenes [231] by regressional analysis, because these compounds are steroid models and the increments, in fact, have proved to be of help in carbon-13 shift assignments of steroids (Section 5.2). Eq. (4.2) permits prediction of <5C using the increments A, of structural elements in position l to the carbon atom k to be considered (Table 4.9). These increments clearly indicate the configurational influence of the y substituent, decreasing for example from eclipsed via gauche to trans interactions (I , > Vq > Vt and... 

Exercise 12-27 The equatorial form of methylcyclohexane is 1.5 kcal mole-1 more stable than the axial form because the axial form has steric hindrance between the methyl and two hydrogens, one in the 3- and the other in the 5-position. Knowing that c/s-decalin is about 2 kcal mole-1 less stable than frans-decalin, what would you estimate for the relative stabilities of cis- and frans-9-methyldecalin (numbering as in Figure 12-22) ... 

Enantiomeric monoacetalization of diones. Acid-catalyzed monoacetalization of cA-9-methyldecalin-l,8-dione (2) with (2R,3R)-( -)-l forms a separable mixture of the diastereomeric monoacetals 3 and 4 in the ratio 9 1. The p-keto acetals 3 and 4 undergo... 

Figure 34.19 Variation of (a) oxygen enrichment factors and (b) air flux constants as a function of plasma polymer coating thickness, perfluro-1-methyldecalin plasma polymer coatings deposited onto porous polysulfone hollow fibers at A 5.35 x 10 J/kg 6.64 X 10 J/kg and 8.05 x 10 J/kg.

Propellane upon hydrogenolysis with Pt/AcOH gives almost equal amounts of the CIS- and trans-angular methyldecalins. ... 

As illustrated in Fig. 20.1, the C-C bond that is broken in the hydrogenolysis of alkyl cyclopropanes is that one between the two least substituted carbon atoms of the ring. With unsymmetrical 1,2-dialkyl-cyclopropanes (1, R iR ) the bond adjacent to the smaller alkyl group is preferentially cleaved. When coupled with the facile cyclopropanation of alkenes, the hydrogenolysis of alkyl cyclopropanes over platinum oxide has served as a useful means of introducing a methyl group onto a tertiary carbon atom as illustrated by the preparation of tert-butyladamantane (3) (Eqn. 20.1) and the 9-methyldecalins, 5 and 6 (Eqn. 20.2). > ... 

No mention was made of the two isomeric methyltetralins and the four stereoisomeric methyldecalins, nor of the many possible isomeric dihydro, hexahydro, and octahydro intermediates. Concentrations of the latter were not likely to have been high enough to be detected without gas chromatography, so that the elemental analyses may principally have reflected mixtures of methylnaphthalene with the two unresolved methyltetralins, and of the latter with the four unresolved methyl-deoalins. 

The increment of energy due to the skew-butane or gauche interaction is variously assigned values of about 0.7 to 1.2 kcal/mole. The value used throughout this contribution is 1.0 kcal. This is a very important parameter because, as will be seen, it permits conformational analysis not only of the cyclohexanes but of the decalins and methyldecalins as well. 

Conformational relationships for the three cis-trans pairs of dimethyl-cyclohexanes were examined by Beckett et al. (34). Here the situation becomes more involved than for methylcyclohexane because some of the isomers are dl pairs, each of which can exist as a pair of chair conformations. However, the conformational analysis of this system merits attention because it will provide a nearly complete basis for the conformational analysis of the deoalins, methyldecalins, and dimethyl-decalins in the following sections. 

The methyldecalin stereoisomers were identified by Weitkamp et al. (3). The assigned structures were confirmed by the nuclear magnetic... 

Methyloctalins of unknown structure from the partial saturation of methylnaphthalene occurred in concentrations comparable to the octalins obtained with tetralin (see Fig. 8) for each of the metals. Distributions of the methyldecalin stereoisomers with various metals... 

The names are abbreviated from cis-syn-1-methyldecalin to CS-1, om [Pg.51]

Fio, 13. Road map showing the role of tetralins and octolins in the formation of the various 1-methyldecalin stereoisomers 1000 psig hydrogen pressure, 100°, 0.6% Ru/AlsOa catalyst. 

Similarly, for the methyloctalins, an axial methyl has a larger effect than an equatorial methyl on the orientation of readsorption. Each of the methyldecalin stereoisomers that was formed in the low yield of 0.5 to 1.0% had as its precursor an octalin whose methyl group not only was axial but was on the side of the molecule facing the catalyst. Most stereoisomers that occurred in yields of 4 to 6% had octalin precursors that could be adsorbed with minimum steric interference. Thus, each not only had an equatorial methyl group but was adsorbed in such a way that the axial geminal hydrogen was directed away from the... 

Methyldecalin Methyl confor- mation Stereo- isomers No. of forms Symmetry No., a No. of gauche interactions Belative cone. Equilibrium at 25° ... 

The relative volatility of tran -onti-2-methyldecalin shifts toward that of trana-ayn-2-methyldecalin at higher temperatures. The actual difference in boiling points at atmospheric pressure may be negligible (see text). 

---