1.1- dimethylcyclohexane-type

Chart 6. Names and Formulas of Type B (Dimethylcyclohexane-Type) Monocyclic Terpene Hydrocarbons and Allied Compounds... 

Monocyclic Type B Dimethylcyclohexane Type 6, p.24 Use Systematic Names (IUPAC Rules) ... 

Rules for Forming Names of Acyclic and Dimethylcyclohexane-Type (Type B) Monocyclic Hydrocarbon Terpene Radicals... 

Dimethylcyclohexane-Type (Type B) lAonocyclics Name the dimethylcyclo-hexane-type (Type B) monocyclic hydrocarbon terpene radicals systematically... 

Application of IUPAC and recognized rules to the naming and numbering of the acyclic and the dimethylcyclohexane-type (Type B) monocyclic compounds. In each of these classes of hydrocarbons there exists no outstanding common terpene name or structure to serve as the basis for developing a logical series of simple terpene-like names. 

Dimethylcyclohexane Type This type of monocyclic terpene hydrocarbon will be named systematically as derivatives of cyclohexane, cyclohexene, and cyclohexa-diene (IUPAC rules). 

This type of reasoning may be applied to other dimethylcyclohexanes, as indicated in the figure. There is no easy way to predict the result it must be deduced in each case. One conformer is of much lower energy in the cases of trans-1,2-, cis-1,3-, and fran -l,4-dimethylcyclohexane both conformers have equal energy in the cases of cis-1,2-, trans-1,3-, and CM-1,4-dimethyIcyclohexane. 

Steric effects affecting the mode of adsorption as well as the type of intermediates formed on different metals are decisive factors in determining product distributions. 1,3-Dimethylcyclohexene and 1,5-dimethylcyclohexene yield an identical mixture of cis- and trims-1,3-dimethylcyclohexane on palladium 63... 

Robert A. Friedel. It would be interesting to carry out the work suggested by Dr. Wender. Type analyses of C naphthenes from a coal hydrogenation product have been reported (2) the types analyzed include ethyl-cyclohexane, propylcyclopentanes, dimethylcyclohexanes, gem-trimethyIcyclo-pentanes, other trimethylcyclopentanes, and methyl-ethylcyclopentanes. Some compounds in these classes could be optically active. Comparable analyses of catalytically reformed petroleum would be of considerable interest in trying to ascertain what optically active components are produced in the reforming. 

When an a-chloroaldehyde or an a-chloroketone is condensed with a /3-ketoester, in the presence of aqueous base, a furan is produced bearing an ester substituent at the /3-position. It is thought that the reaction is of the aldol type intermediate dihydrofurans (256) have been isolated in certain cases (Scheme 70) (74BSF519). The condensation of ethyl bromopyru-vate and sodium oxaloacetate follows a similar mechanism (54JOC1671). The one-pot synthesis of 2,4,5-trisubstituted furans (257) from ketones and ethyl 3,4-dibromo-2-butenoate is a useful addition to a well known route (80S52). The analogous reaction of cyclic /3-diketones, i.e. cyclohexane-1,3-dione and 5,5-dimethylcyclohexane-l,3-dione, results in the formation of the condensed furans (258) and (259). These reactions are preformed either in ethanol with sodium ethoxide or in DMF with potassium carbonate. 

Type B. Those which contain no iso three-carbon group. Most of the hydrocarbons of this type, for which structures have been proved, contain two one-carbon groups in gem configuration and one or two additional isolated one-carbon or two-carbon groups, one of which is usually in meta position. These structures could be further divided into those that contain the gem-dimethyl configuration and those that do not, but their similar chemical reactivity warrants classification as a single group of compounds. Thus, Type B monocyclics may be considered as derivatives of dimethylcyclohexane, for which no trivial name has been well established. 

The first few Type B (derivatives of dimethylcyclohexane) terpene monocyclic hydrocarbons that were discovered had the empirical formula and were... 

The cis- and trans-stereoisomers of cyclic compounds that were presented previously are actually just special cases of the type of stereoisomers that we have just discussed. For example, consider the case of 1,2-dimethylcyclohexane ... 

Knoevenagel condensation of aldehydes with malononitrile under mechanochemi-cal mixing in the presence of MgO resulted in adducts of general structure 138 (Scheme 27), which were further treated with either ethylacetoacetate or 5,5-dimethylcyclohexane-l,3-dione to provide products 139 and 140 [63]. The transformation of 138 and 139 or 140 proceeded via a Michael-type nucleophilic addition of the enolizable ketoester or dione, followed by intramolecular cyclization. 

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. 

Mynderse, J.S. and Faulkner, D.J., 1975b. (lR,2S,4S,5R)-l-bromo-frans-2-chlorovinyl-4,5-dichloro-l,5-dimethylcyclohexane, a new monoterpene skeletal type from the red alga Plocamium uiolaceum. Tetrahedron Lett., 1975 2175—2178. 

By the study of 12 isotopomers of protoadamantane, the stereochemical dependence of isotope effects was also observed. A Karplus-type relationship similar to that for spin-spin coupling constants was proposed Recently, the first quantitative stereochemical dependence between isotope effects and dihedral angle was reported for a series of deuteriated norbornanes, as shown in Figure Observations of the influence of substitution with deuterium on conformational equilibria led to a new method in physical organic chemistry called isotopic perturbation of equilibrium. Details can be found in a recent review The effect was first observed for the chair-tO"Chair interconversion of deuteriated 1,3-dimethylcyclohexane 43 and later in 4-ethyl-l-methylcyclohexane " as well as in 1,1,4,4-tetramethylcyclohexane. In contrast, the isotope effect on conformational equilibrium in related systems turned out to be too small to be observable... 

To summarize, a molecule with an axis of symmetry possesses rotational symmetry, and a molecule with a plane of symmetry possesses reflectional symmetry. With an understanding of these two types of symmetry, we can now explore the relationship between symmetry and chirality. In particular, chirality is not dependent in any way on rotational symmetry. That is, the presence or absence of an axis of symmetry is completely ttrelevant when determining whether a compound is chiral or achiral. We saw that tnt f-l,2-dimethylcyclohexane possesses rotational symmetry nevertheless, the compound is still chiral and exists as a pair of enantiomers ... 

The radical mechanism is further supported by several other results in which stereochemical scrambling and isotope scrambling are observed in the sMMO-catalyzed hydroxylation of hydrocarbons. Retention of stereochemistry is a valid measure of the concertedness of a reaction only if it can be assumed that the retention is not due to constrains imposed by the active site geometry of the enzyme. Loss of stereochemistry is absolutely indicative of a reaction requiring an intermediate and thus implies a nonconcerted reaction [2]. Scrambling of stereochemistry was observed with hydroxylation of c/5-l,4-dimethylcyclohexane and c/ -l,3-dimethylcyclohexane with sMMO system from Af. capsulatus (Bath) as shown in eqs. (7) and (8) [75]. This type of stereochemical scrambling was also observed in the hydroxylation of norbornane by rabbit liver microsomes and in the oxidation of camphor by cytochrome P-450 [2]. 

If we now consider the NMR spectrum of the keto and enol tautomers of dimedone (5,5-dimethylcyclohexane-l,3-dione), another puzzle emerges (Figure 17.8). Despite the fact that there can be no intramolecular hydrogen bond, the enol form still appears to be symmetrical— only one type of CHj. At equilibrium, about 40 % of the material is enolized. It is suggested that under these conditions, the material is part of a dimeric structure, 17.17, in which rapid proton transfers are possible. However, in very dry dimethylsulfoxide, NMR spectroscopy suggests that dimedone is completely enolized, and monomeric, with distinct CHj carbon atoms. 

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