Tricyclic hydrocarbons

Treatment of the alcohol whose structure is shown here with sulfuric acid gave as the major organic product a tricyclic hydrocarbon of molecular formula CigHig. Suggest a reasonable structure for this hydrocarbon. 

It is probable that the tricyclic hydrocarbon from sandalwood oil is identical with, or at least closely allied to, Semmler s nor-tric /cZoeksanta-lane. 

Bond-Stretch Isomerism and the Reactivity of some Highly Strained Tricyclic Hydrocarbons towards Acids and Bases... 

Huang, Y. Peakman, T.M. Murray, M. (1997) 8p,9a,10p-Rimuane a novel, optically active, tricyclic hydrocarbon of algal origin. Tetrahedron Lett., 38, 5363-6. 

A 13C-NMR study645 on the stereochemistry of perhydronaphthaleno[2,l-e]pyrido[l,2-c -[l,3]oxazines 5 was based on comparisons with bi- and tricyclic hydrocarbons (bicy-clo[4.4.0]decanes and perhydrophenanthrenes) and related heterocyclic analogs, such as quino-lizidine 6 and perhydropyrido[1,2-c][l,3]oxazine 7. 

This alkynone thermolysis has served as the key step in several natural product syntheses. The considerations that lead to regio- and stereochemical control are illustrated by an elegant synthesis of clovene 725. Thermolysis of the symmetrical alkynone 4 could lead to three different enones, two of which (5 and 6) arc illustrated. In fact, only 8-methyltricyclo[8.3.1.01 5]dodec-3-en-2-one (5) is isolated, in 80% yield. The structure of 5 was confirmed by straightforward conversion to the tricyclic hydrocarbon clovene. The outcome of the thermolysis was anticipated, as it had previously been observed that C-H insertion is most facile when the intermediate alkylidene can achieve coplanarity with the target C-H bond. In this system, such coplanarity is achievable only via the boat conformation of one of the two symmetrical rings. 

Substitution of the acetylenic hydrogen atom in 1-ethynylsilatrane by a phenyl group slightly increases the toxicity. The presence of bi- or tricyclic hydrocarbon radicals at the silicon atom leads to a greater increase in toxicity (the LDS0 value for compounds (30) and (41) is 850 and 80 mg/kg, respectively). 

One other farily strained adamantoid molecule which has been found to be readily available via the rearrangement route is noradamantane (23). Brexane (24), a C9 tricyclic hydrocarbon, rearranges smoothly in the presence of A1C13 to the lower adamantane homologue, 23, in 75 % yield (Eq. (11)) 36 This rearrangement, however, is consistent with thermodynamic principles. (See Section 111. E and Scheme 8 for other preparations of this hydrocarbon). 

A new tricyclic hydrocarbon, senoxydene, which has been isolated from Senecio oxyodontus, has been assigned the structure (304) on the basis of its n.m.r. spectrum together with that of the corresponding epoxide.It is suggested that once again humulene could act as the precursor (Scheme 48) see, however, p. 104. 

A few specific examples of cyclopropanation using the above methods are shown in Scheme 2.134. The naturally occurring insecticide /ra -chrisanthemic acid 396 served as an obvious target to check the viability of carbene addition as a preparative method. This compound was first synthesized (in the mixture with the cis isomer) by the monocyclopropanation of 2,5-dimethyl-2,4-hexadiene. Since then, numerous analogs of 396 were prepared by similar reactions. Some of the analogs are now widely used as efficient and ecologically safe pesticides. The formation of the tricyclic hydrocarbon 397 from 1,5-hexadiene proceeds as a sequence of inter- and intramolecular carbene transfer reactions. An initial carbene precursor, CHBr3, is actually employed here as an equivalent of a unique tetradentate Ci synthon The preparation of 398 via intramolecular [2 + 1] photocycloaddition is a typical example of the efficiency of this route for the construction of the polycyclic framework frequently encountered in the structures of natural compounds. 

Bicyclo[3.3.0]oct-l(5)-ene 178 (Scheme 4.55) is a stable compound with a flattened alkene fragment and exhibits a regular pattern of reactivity. Computational studies revealed, however, that installation of a short 3,7-bridge should lead to noticeable pyramidalization of the double bond. Compounds like 179-181 were synthesized to check this prediction. Tricyclic hydrocarbon 179, with the smallest possible bridge, was generated as a transient species from diiodide 182. The formation of 179 is implicated by the isolation of its cyclodimer 183 (or respective Diels-Alder adduct if the reaction is carried out in the presence of a 1,3-diene). The next member of this series, 180, is more stable. In fact, the formation of 180 was ascertained not only from the structure of the final products (as was done for 179), but also by its matrix isolation and analysis of spectral data. The selenium derivative 181 was found to be stable at ambient temperature in the absence of oxygen. X-ray data confirmed a noticeable pyramidalization of the double bond in 181 but the distortion was different [Pg.372]

Adamautane synthesis. Irish chemists report a new catalyst that is much more elTective than the so-called AIBry sludge catalyst (2, 20) for isomerization of strained tricyclic hydrocarbons into adamantanes. The catalyst is prepared from alumina and chloroplatinic acid followed by sequential treatment with H2, HCl, and SOCIj. The catalyst can be reactivated by treatment with Oj at 500° and then repetition of the H2-HCI SOCI2 treatment. 

The reaction can be extended to tricyclic hydrocarbons with a norbornene substructure, such as exo- and e Jo-tricyclo[5.2.1.0 - ]deca-3,8-diene (17). ° Side products are the [2 + 2] cyclo-... 

A cyclic variant of the above rearrangements is provided by 43 (whieh was actually not pyrolyzed in pure from but rather in a mixture with its diastereomer 46). Heating 43 in a flow system at 250 °C for 45 seconds yielded the tricyclic hydrocarbon 45 and the cycloallene 46 which... 

C12 hydrocarbon (271)135 by a similar route but this compound is not identical to a tricyclic hydrocarbon isolated from East Indian sandalwood oil and reported to have this structure. (+)-Copacamphor (272) and (+)-copaborneol (273) have been isolated from Espeltiopsis guacharaca.136 The interesting sinularene derivative (274) and the acetoxycyclosinularane (275) have been isolated from the marine source, Clavularia inflata.137 These compounds, together with an aromadendrane derivative (see p. 181) are the first sesquiterpenoids from Octocorallia of the order Stolonifera. 

Anthranoid laxative plants The anthranoid-containing plants are essentially similar in their mode of action. In this group the active substances are a group of polynuclear or tricyclic hydrocarbon derivatives based on anthracene. Various oxidised and reduced forms constitute the aglycones of a variety of C and O glycosides. The fully oxidised form is the anthraquinone form, with the partially reduced form represented by the an-throne nucleus. Dimeric forms whereby two anthracene nuclei are chemically linked to... 

Richardson, J.S. and D.E. Miller 1982. Identification of dicyclic and tricyclic hydrocarbons in the saturate fraction of a crude oil by gas chromatography/mass spectrometry. Anal. Chem. 54 765-768. 

C2 symmetry), a high-symmetry chiral cage-shaped tricyclic hydrocarbon closely related to D2 twistane. Wagner-Meerwein rearrangement (144) of the unsaturated carboxylic acid (-)-151 provided the lactone (-)-168, which in turn was converted into the ketone (+)-170 via a series of intermediates, including the mesylate 169 whose intramolecular alkylation was a crucial step in this approach. Removal of the carbonyl group by Wolff-Kishner reduction completed the synthesis of (+)-brexane (171) (145). 

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