Bicyclo decane group

Intraactions between elections in three-membered rings and unsaturated groups in the same molecule have been detected via 13C chemical-shift variations in a number of instances. Thus, introduction of the carbonyl function in tricy-clo[3.2.1,02,7]decane (e.g., 274) leads to significant downfield shifts of the signals of C(l) (+8.0), C(2) (+15.5), and C(7) (+7.7) (385), whereas corresponding effects in bicyclo[3.1.0]hexan-2-one (275) are smaller (385,386). A corresponding dependence was reported for 276 and 277 and related to more effective electron withdrawal in 276 (387). An even more pronounced deshielding effect was observed by Murata and co-workers (388,389) in the ketone 278 when they compared it with 279. 

There are few published H-NMR data for bicyclo[4.4.0]decanes (decalins) one paper describes effects of hydroxy and methoxy groups on chemical shifts346. 

J.K. Cha et al. developed a stereocontrolled synthesis of bicyclo[5.3.0]decan-3-ones from readily available acyclic substrates. Acyclic olefin-tethered amides were first subjected to the intramolecular Kulinkovich reaction to prepare bicyclic aminocyclopropanes. This was followed by a tandem ring-expansion-cyclization sequence triggered by aerobic oxidation. The reactive intermediates in this tandem process were aminium radicals (radical cations). The p-anisidine group was chosen to lower the amine oxidation potential. This substituent was crucial for the generation of the aminium radical (if Ar = phenyl, the ring aerobic oxidation is not feasible). 

The methylene-bridged bicyclo[4.4.0]dec-8-ene-3-one 7 and -decan-3-one 8 reacted in a similar fashion when treated with hydrogen chloride, but cleavage of both cyclopropane bonds between the bridgehead atoms and the methylene group was observed. For stabilization hydrogen chloride was eliminated to give a double bond. 

On the basis of both synthetic and degradative studies, Marshall and co-workers have shown that the structure of -vetivone based on a bicyclo-[5,3,0]decane skeleton is untenable and subsequent work dictated the structure (326) incorporating a spiro[4,5]decane skeleton, and this they have confirmed by total synthesis. The method employed was the selective introduction of an isopropylidene group in a stepwise fashion starting with the keto-olefin (327), which was obtained via photolysis of the known dienone (328). 

Reactions of the (3S ) and (3R )-3-chloro-2,4,7-trioxa-3-phospha-bicyclo-[4.4.0]decane 2-sulphides (88) with nucleophiles proceed with predominant inversion of configuration at phosphorus. Differences in rates of displacement of axial and equatorial leaving groups were observed in, for example, propanolysis. Two studies have dealt with thiol-thione isomerization. The conversion of a S5mimetrical monothiopyrophosphate into its unsymmetrical isomer has, thus far, been considered in terms of a cyclic process, but a dissociative mechanism is now proposed. In the free base form, the esters (89) can be rather unstable, although stabilization is achieved as the oxalate salts. The isomerization of the free base into the, S55-triester may be intramolecular, reversible, and of first order (e.g., for R = Et or Bu, R = Et, n = 2), or it may be irreversible, intermolecular, and of second order (e.g., for R = Pr, R = Et, n = 3). ... 

A synthetically useful example of this process is the conversion of 117 to 120, which involves a 1,2-alkyl shift, and was part of Hwu s synthesis of (-)-solavetivone. 38 jhe alkyl fragment is actually part of the bicyclic ling system, one arm of the bicyclo[4.4.0]decane ring system. Reaction of the OH unit with the Lewis acid resulted in formation of the tertiary cation 118, which was followed by a 1,2-alkyls shift to give 119, where the new cation is stabilized by the adjacent silicon of the trimethylsilyl group. 39 Loss of the trimethylsilyl group from 119 gives spiran (120). 

Deprotonation of the dication cij-1,6-dimethyl-l,6-diazoniabicyclo[4.4.0]decane (66) results in products derived from deprotonation at a methyl group, including 1-methyl-l-azonia-6-bicyclo[4.4.1]undecane (67) <84JCS(P2)4ll, 86J0C3169>, and deprotonation of the dication of 6-methyl-l,6-diazoniatricyclo[6.2.2.0 ]dodecane (68) affords the monoion of 1-methyl-l-azonia-6-aza-tricyclo[7.2.1.0 "]dodecane (69) <86JOC3i69>. 

Substrates 46 (E Z =5.5 1) and 48 were selected for study because of the number of naturally occurring bicyclo[5.3.0]decanes bearing an angular methyl group and because of the general difficulties associated with quaternary center formation. These methyl-substituted substrates (46 and 48) react rapidly (reaction times 1 h) and with high efficiency (>90%) to afford exclusively the cw-fused products 47 and 49, respectively (Eqs. 59 and 60). In these cases, silver triflate is required for clean conversion. In its absence, decomposition occurs more rapidly than cycloaddition. At higher substrate concentration and... 

The same kind of rearrangement has been utilized in an intramolecular sense to transform the much more readily available decalin system into the bicyclo[5.3.0]decanes of the guaiane and pseudoguaiane sesquiterpenes. Thus, the Heathcock group synthesized confertin, as shown in Scheme 46 [82]. 

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