Decalins, substituted

It is a typically aromatic compound and gives addition and substitution reactions more readily than benzene. Can be reduced to a series of compounds containing 2-10 additional hydrogen atoms (e.g. tetralin, decalin), which are liquids of value as solvents. Exhaustive chlorination gives rise to wax-like compounds. It gives rise to two series of monosubstitution products depending upon... 

Thermolysis of the hexamethyl-substituted Dewar benzene-phenylazide adduct 1 in refluxing Decalin affords the 1.2,3-triazonine derivative 2 as the major product in form of a yellow-orange powder.30 A bicyelic isomer is also isolated which arises from rearrangement of 2 by purification on alumina and is readily converted back to 2 on heating to 80 C. 

The extensive study of Craig and coworkers [116] on the intramolecular Diels-Alder reactions of E- and Z-sulphonyl-substituted deca-, undeca- and dodecatrienes 120 (Figure 2.13) has opened a short route to trans- and cis-bridgehead hydrindanes and decalines and has given new insights into the role of dienophile substitution and geometry in determining the stereochemical outcome of these intramolecular cycloadditions. 

Huisgen et al. also studied the thermal decomposition of ethyl diazoacetate in the presence of benzonitrile and phenylacetonitrile to give the corresponding 2-substituted-5-ethoxy oxazoles 3 in variable yields (Scheme 3).<64CB2864> The authors found that the solvent had an effect on the rate of decomposition of ethyl diazoacetate in the polar solvent, niuobenzene, the rate was found to be twice that in the hydrocarbon solvent, decalin. 

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. 

In cases where a simple reductive elimination cannot take place. Si—M cleavage may still occur, as shown in Eqs. (81) 217) and (82) (R = Me, f-Pr, Ph) 103, 207). When the reaction of Ph3SiMn(CO)5 with PPh3 was carried out at 130° C in decalin, only the substitution product Ph3SiMn(CO)4PPh3 was observed 103, 207). 

The two-term rate law for substitution reactions of the group VI hexacar-bonyls has been previously mentioned (see p. 29) and it will be useful to summarize the evidence for associative activation in this case. i. There is reasonably good agreement between the rate of exchange in the gas phase and the first-ot tv rate of substitution in decalin, suggesting that this term represents a dissociative reaction. 

Entry 6 shows a stereoselective formation of a highly substituted frans-decalin system. The reaction in Entry 7 establishes a taxanelike structure. The stereochemistry is consistent with a TS in which both the carbonyl oxygen and the methoxy group are coordinated to aluminum. 

A SN reaction-based domino route to clerodane diterpenoid tanabalin (2-488) [258] has been described by Watanabe s group (Scheme 2.111) [259]. This natural product is interesting as it exhibits potent insect antifeedant activity against the pink bollworm, Pectinophora gossypiella, a severe pest of the cotton plant The domino sequence towards the substituted trans-decalin 2-487 as the key scaffold is induced by an intermolecular alkylation of the (5-ke toes ter 2-484 with the iodoalkane 2-483 followed by an intramolecular Michael addition/aldol condensation (Robin-... 

The kg value was determined to be about 6.9 x 10" s independent of the nature of L in 50°C decalin (AH - 31.8 kcal mol-1 AS - +20.2 cal mol 1 K l). Competition ratios k.g/ky equal to 3 and 5 were determined for L - P(OPh3)3 and PPI13, respectively under the same conditions. The second order pathway was proposed to occur via nucleophilic attack of L on the cluster, and an intermediate with a formulation the same as II/ was suggested, without supporting evidence of its existence, as a possible initial product of this nucleophilic attack. However, since fragmentation was only a minor side reaction of the substitution reactions with L - PPI13, it is quite unlikely that the photofragmentation and second order thermal substitution reactions occur via a common intermediate. 

Thus reactions of t-Bu4Sb4 with [Cp Mo(CO)3]2 at elevated temperatures in toluene or decalin lead to the substitution of alkyl groups with formation... 

Starting from quinic acid, a highly substituted, cis-afi unsaturated nitrile oxide has been synthesized and used in a 1,3-dipolar cycloaddition, to afford a precursor of the cis -decalin system of branimycin (468). 

Fig. 12 Cetane number of intermediates and products of the reaction pathway of metal-catalyzed ring opening of decalin via substituted carbon center. Adapted from ref. 12.

Conformational inversion barriers of 5,10-substituted decalins (17) were determined by NMR, and MMI calculations were carried out to see whether the twist-chair (ct) or the boat-boat (bb), correspond to the higher barrier. The ct was found to be higher in cw-decalin (17, R = H), but the introduction of substituents at the ring junction is expected to raise the energy of the bb. The observed AG agreed with the calculated value for ct, which is about 5 kcal/ mol higher than that of bb when R = CH3 or OH (124). 

Regioselective Substitution of Unactivated CH Bonds CH bonds in cycloalkanes (decaline, steroids) and alkanes bearing electron-deficient groups in remote posihons (1,2-dichlorocyclohexane, decanoic acid) can be regioselectively subshtuted at the anode by trifluoroacetate, acetate, or methoxide (Figs. 1, 2) [12-14]. 

On the other hand, in the synthesis of cholesterol (30) by Woodward and CO workers [10] the less stable fran -configuration between rings C and D is attained through a homosteroid (29). i.e. a steroid analogue in which the C/D indane system is substituted by a decalin in which the rran -configuration is the thermodynamically favoured (Scheme 8.7). The conversion of the six-membered ring into one of five members is carried out at a later stage, under conditions that do not affect the preformed tran -junction. 

The 1,2-carbonyl transposition takes place through the enJo-epoxide 18 easily prepared through the tosylhydrazone 16, followed by regioselective cleavage to the less substituted double bond (17) with 2 equivalents of methyllithium [4] and epoxidation with MCPBA in chloroform from the more accesible convex face of the decalin system. 

The second group of compounds are the oxa-decalins, which can exist in cis-39 and trans-39 anellation (Scheme 21). 2,4-Di-substituted 1,3-dioxa-decalins exist as a mixture of cis- isomers, the oxygen in O-in conformation... 

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. 

It has been reported that [I,5]diaza-m-decalins undergo an oxidative rearrangement, at the mote hindered position, followed by fragmentation to give the ring expanded bis-lactam (Scheme 11). If the iV-BOC-protected compound was used, oxidation occurred at the less hindered position to give a route to 2,6-substituted-I,5-diaza-ar-decalins <2002TL3747>. 

Scott Denmark of the University of Illinois reports (J. Org. Chem. 68 8015,2003) a hetero intramolecular Diel-Alder reaction of a nitro alkene 5, followed by intramolecular dipolar cycloaddition of the resulting nitronate 6, to give the tricycle 7. Raney nickel reduction effected cleavage of the N-0 bonds and reductive amination of the liberated aldehyde, to give, after acetylation, the angularly substituted cis-decalin 8. 

This electrophilic substitution is unique among chemical transformations, in the sense that a reaction takes place on a completely deactivated site difficult to access by other reactions. With fluorine as a reagent, decalins, bicyclohexyls, alkylcycloalkane derivatives 6-8 and many more can be fluorinated at their tertiary position and subsequently dehydrofluorinated.37... 

Eastman Kodak o-dichlorobenzene of 95% purity was used. Olefin-free kerosene or decalin may be substituted for the solvent, keeping the reaction temperature between 170° and 190°. 

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