Bicyclo decane ring

The decalin (bicyclo[4.4.0]decane) ring system provides another important system for study of conformational effects in cyclohexane rings. Equilibration of the cis and trans isomers reveals that the trans isomer is favored by about 2.8 kcal/mol. Note that this represents a change in configuration, not conformation. The energy difference can be analyzed by noting that the cis isomer has three more gauche butane interactions that are... 

The key bond closure in Scheme 13.21 is somewhat similar to that used in Scheme 13.20 but is performed on a bicyclo[4.4.0]decane ring system. The ring juncture must be cis to permit the intramolecular epoxide ring opening. The required cis ring fusion is established during the catalytic hydrogenation in step A. 

A good deal of effort has been devoted to the preparation of derivatives of the cyclohepta[cd]indole and bicyclo[4.3.1]decane ring systems, that can be considered related to the ABC and CD ring systems of welwistatin, respectively, but much of this work cannot be translated easily to methods relevant to welwistatin synthesis. For instance, many successful approaches to the cyclohepta[cd] indole system are based on intramolecular radical cycliza-tions [12] or Heck reactions [13]. In many published examples, a substituent at the indole C-2 avoids the competing reaction at this position, but this device renders the reaction products inadequate to achieve the oxindole struc-... 

Many oligomers have complicated cyclic rings. Suffmticosol A (589) and its stereoisomer suffmticosol B (590) have a bicyclo[5.3.0]decane ring system, whereas suffmticosol C (591) possesses an unusual [6.2.1] dode-... 

A tandem ring expansion followed by cyclization of l-(trimethylsiloxy)bicyclo[4.1.0]heptanes substituted with unsaturated side chains at C5 has been developed for the construction of bicyclo[5.3.0]decane ring systems, e.g. conversion of 19 to 20. ... 

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). 

Three modified clerodanes 9, 10 and 11 were extracted from Dodonaea viscosa. These compounds have been proposed as hypothetical intermediates in the biosynthesis of diterpenes containing bicyclo[5.4.0]undecane or bicyclo[5.3.0]decane ring systems <01T2981>. Three furoclerodanes, namely 12-epi-Teukotschyn, teughrebin and 12-epi-... 

N,N-Betaines s. Aminimides Betti 1,3-oxazine ring closure 10, 578 22, 778 Bi... s. a. Di... Bicyclo[1.1.0]butane ring opening, double -, diene synthesis with - 31, 654 Bicyclo[5.3.0]decane ring s. Azulenes... 

Bicyclo[4.3.1]decane from bicyclo[4.2.2]decane ring... 

In 2010, Wender et al. reported a cascade reaction by combining Rh and Ag catalysis, affording the commonly encountered bicyclo[5.3.0]decane ring systems [15]. This chanistry merged a Rh-catalyzed intermolecular [5+2] cycloaddition and a Lewis add-promoted Nazarov cycUzation, highlighting the cascade catalysis in the facile construction of natural product scaffolds (Scheme 9.12). 

Aphanamol 1181 is a member of the isodaucane family of sesquiterpenes, which contains a bicyclo[5.3.0]decane ring (Figure 19.19). Interest in this compound is derived from the meliaceous iplsaAAphanamixis grandifolia from which it was isolated [89]. One of the first natural products prepared utilizing an intramolecular [4+3] cycloaddition was aphanamol I as executed by Hannata and Carter [90]. 

The natural product lasidiol 217 (Figure 19.23) is a member of the daucane class of sesquiterpenes, which contain a bicyclo[5.3.0]decane ring system [106]. While studying the utility of intramolecular [4-1-3] cycloaddition reactions, Kreisehneier and Fohlisch accomplished a total synthesis of racemic lasidiol [107]. 

The bicyclic compound decahydronaphthalene, or bicyclo[4.4.0]decane, has two fused six-mem-bered rings. It exists in cis and trans forms (see Fig. 1.10), as determined by the configurations at the bridgehead carbon atoms. Both cis- and rran -decahydronaphthaiene can be constructed with two chair conformations. 

Among the most important of the bicyclic hydrocarbons are the two stereoisomeric bicyclo[4.4.0]decanes, called cis- and rrani-decalin. The hydrogen atoms at the ring junctions are on the same side in c/5-decalin and on opposite sides in tmns-AecdXm. Both rings adopt the chair confonnation in each stereoisomer. 

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. 

This holds only if the ring fragment is conformational ly rigid, for example, due to the presence of voluminous substituents ( steric anchors ) or incorporation into a rigid polycyclic system such as /raws-bicyclo[4.4.0]decanes (decalins) or steroids. 

Empirically, y-gauche effects are extremely useful in stereochemical analysis. For example, the cis- and trans-fusion of six-membered rings can be easily differentiated, since, in contrast to the trans-isomer of bicyclo[4.4.0]decane, there are gauche-butane fragments in the m-isomer (emphasized bonds) causing upheld signal shifts of the carbons involved (numbers refer to I3C chemical shifts in ppm)49-52. 

Polycyclic compounds have more than one ring those with exactly two rings are bicyclic. The rings may merely be bonded to each other, as in Problem 9.1(d). Those that share a C—C bond are said to be fused, as exemplified by decalin (bicyclo(4.4.0]decane). The C s that are common to the two rings, shown encircled in decalin below, are called bridgehead C s. 

The conversion of a cycloheptanone to a bicyclo[5.3.0]decane derivative can be effected through ring opening of an intermediate furfurylidene derivative (57JA6023). Thus, condensation of 2-methylcycloheptanone with furfuraldehyde in the presence of sodium methoxide gave (61). On heating with concentrated hydrochloric acid in ethyl alcohol, the ketovaleric acid (62) was produced which on aldolization furnished the bicyclic ketone (63) in 17% overall yield (Scheme 15). 

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