Cyclohexane compounds

Formation of aromatic compounds involves either the dehydrogenation (by way of reaction with carbonium ions) of the cyclohexane compounds or, less likely, the cyclization of a triolefinic carbonium ion. 

All 1,2-1,3-and 1,4-disubstituted cyclohexane compounds used in the study under discussion were a mixture of the cis and trans forms. 

In the first instance, only cyclohexane compounds with hydrogen atoms substituted will be considered, so that there should be no drastic alteration of the ring skeleton. In Table 2 are listed values of barriers to ring inversion in cyclohexyl hahdes where these are known to a reasonable accuracy.35-37) There is no doubt that there is a significant difference between the values for fluorine and chlorine, but bromine occurs between these two values. The barriers to rotation in the series CH3CH2X 38) and in the series (CH3)2CX—C(GH3)3 39) are also quoted in the table, but the trends there are not reflected in the results for ring inversion. 

The racemic lactone ( )-18 was obtained as a pure and crystalline compound, and its relative stereochemistry had to be determined. I thought, in 1960, XH NMR analysis to be the most appropriate method to solve the problem, because it had already been known to use a vicinal coupling constant for the stereochemical studies of cyclohexane compounds including terpenoids and steroids. Figures 1.13(a) and (b)... 

Even though the eorrelation is found to be highly significant, the difference in potency between the trans-and cis-diastereomers of the cyclohexane compound cannot be explained by the calculated lipophilicity (see Fig. 

The reduction of keto-cyclohexane compounds, including some inososes,i has been widely studied and it has been found that hindered keto groups afford axial hydroxyl groups, and that the proportion of axial to equatorial hydroxyl groups formed is dependent on the type of reduction. It was found that the results with the keto-pyran compounds (the keto-D-gluco-pyranosides) were rather similar to those obtained with the related keto-cyclohexane compounds (the inososes). 

The quantitative estimate of the magnitude of the anomeric effect must take into account the steric preference of an electronegative substituent larger than hydrogen for the equatorial orientation in the corresponding cyclohexane compound. In order... 

Two compounds, A and B, have the same molecular formula, CeHa. Both A and B react with two molar equivalents of hydrogen in the presence of platinum to yield cyclohexane. Compound A shows three signals in its broadband decoupled NMR spectrum. Compound B shows only two NMR signals. 

Cyclopentane and cyclohexane compounds have been prepared by employing chelation-controlled stereoselective vinylmagnesium bromide additions to aldose sugars, and subsequent construction of the carbocyclic rings by intramolecular nitrone cyclization using Bernet and Vasella s methodology as illustrated for the amino-... 

Further structure determinations of cyclohexane compounds have been carried out by X-ray analysis. The crystal and molecular structure of (7) was determined in part for identification purposes. The bond length of the exo-cyclic C-4—C-7 bond was found to be 1.55(1) A. The structure determination of (8) indicates that both bromine and phenyl are axial and that the benzene rings are inclined to each other at an angle of 37.5° in the solid state. 

Because the steroid ring system is rigid, functional groups bonded to ring atoms have well-defined positions. Substituents below the plane of the ring are designated as a those above the plane of the ring are P. We recall that down and up in substituted cyclohexane compounds are not synonymous with equatorial and axial. For the same reasons, this method of nomenclature for steroids does not indicate whether the substituent is equatorial or axial. 

---