Bicyclo nonanes, structure

Bicyclo[3.3.1]nonan-9-one is another ketone that exhibits interesting stereoselectivity. Reduction by hydride donors is preferentially syn to electron-attracting substituents at C-5 (X = EWG in the structure shown below) and anti to electron-releasing substituents (X = ERG below). These effects are observed even for differentially substituted phenyl... 

The potential of Fischer carbene complexes in the construction of complex structures from simple starting materials is nicely reflected in the next example. Thus, the reaction of alkenylcarbene complexes of chromium and tungsten with cyclopentanone and cyclohexanone enamines allows the di-astereo- and enantioselective synthesis of functionalised bicyclo[3.2.1]octane and bicyclo[3.3.1]nonane derivatives [12] (Scheme 44). The mechanism of this transformation is initiated by a 1,4-addition of the C -enamine to the alkenylcarbene complex. Further 1,2-addition of the of the newly formed enamine to the carbene carbon leads to a metalate intermediate which can... 

The direct synthesis of the fused ring compound (55) from the reaction of phosphorus trichloride with ethylamine hydrochloride has already been described (Scheme 16). Its N-methyl analogue (67) can be obtained from the reaction of (MeNPX)3 (X = Cl or Br) with heptamethyldisilazane (Scheme 19). The identification of the structures of these fused-ring compounds, which are structurally related to the bicyclo(3.3.1)nonane carbocycles, pose difficult problems. An example of their... 

Introduction of the allene structure into cycloalkanes such as in 1,2-cyclononadiene (727) provides another approach to chiral cycloalkenes of sufficient enantiomeric stability. Although 127 has to be classified as an axial chiral compound like other C2-allenes it is included in this survey because of its obvious relation to ( )-cyclooctene as also can be seen from chemical correlations vide infra). Racemic 127 was resolved either through diastereomeric platinum complexes 143) or by ring enlargement via the dibromocarbene adduct 128 of optically active (J3)-cyclooctene (see 4.2) with methyllithium 143) — a method already used for the preparation of racemic 127. The first method afforded a product of 44 % enantiomeric purity whereas 127 obtained from ( )-cyclooctene had a rotation [a]D of 170-175°. The chirality of 127 was established by correlation with (+)(S)-( )-cyclooctene which in a stereoselective reaction with dibromocarbene afforded (—)-dibromo-trans-bicyclo[6.1 0]nonane 128) 144). Its absolute stereochemistry was determined by the Thyvoet-method as (1R, 87 ) and served as a key intermediate for the correlation with 727 ring expansion induced... 

Some partially fluorinated bicyclo[3.2.2]nonanes have also been fluorinated120 over co-balt(III) fluoride, and, as with the partially fluorinated bicyclo[2.2.2]octanes, the skeletal structure remains intact. 

Majetich reports that the fluoride ion catalyzed carbocyclization of ally anion equivalents to a, 3-enones is sensitive to the structure of the a,p-enone in which competing 1,2- and 1,4-addition processes occur.116 For example, a,(3-enones (135) afford predominantly the jyn-bicyclo[4.3.0]nonan-3-ones (136)... 

Phosphabicyclo[3.3.1]nonanes 146a and 146b were converted into the phosphinic acid, 4,8-dimethyl-2-phospha-bicyclo[3.3.1]nonan-2-ol 2-oxide 147, upon treatment with hydrogen peroxide under acidic catalysis. The structure of phosphinic acid 147 was accomplished by an X-ray analysis. Additionally, it was shown that if phosphines 146a and 146b were exposed to air, they underwent a rapid oxidation to yield the ammonium salt of 2-(4-methylcyclohexyljpropylphosphonic acid 148, whose structure was also confirmed by the X-ray analysis <2001TL2609>. 

Another group of polymers with good heat resistance includes certain aryl-alicyclic compounds. They are generated from the polycondensation of 4,4 -diaminodiphenyl oxide with various anhydrides such as tricyclo[4,2,2,0 ]dec-9-ene-3,4,7,8-tetracarboxylic acid anhydride, 9-oxatricyclo[4.2,2,0 ]nonane-3.4,7,8-tetracarboxylic acid anhydride, cyclobutene-1,2,3,4-tetracarboxylic acid anhydride, and bicyclo[2,2,2]octane-23,5,6-tetracarboxylic acid anhydride. Thermal stability of these polymers is affected by the ring stability (strain) regardless the true chemical structure. Pyrolysis at 650° C generates some compounds that are the same in nature and some others that are characteristic for each polymer. The main decomposition paths, as indicated by the main pyrolysis products are shown below for each polymer (Ar = 4,4 -diphenylene oxide) ... 

Secondly, make a mode of the hindered alkene 43 this shows that it is sterically impossible for bromine to bond with the alkene carbons other than by a top or bottom approach. To construct a molecular model of 43, make two models of bicyclo[3.3.1]nonane, with both cyclohexane rings in a chair conformation. Identify carbons C(3) and C(7) in each of these structures then take a molecule of ethene and use C(l) of ethene to bond to C(3) and C(7) of one bicyclic structure, and C(2) of the alkene to bond to C(3) and C(7) of the other structure. The result is the hindered alkene 43, Examination of this model, together with an understanding of the orientation of the double bond, indicates that steric factors permit isolation of the bromonium ion. 

Benyhe S, Marki A, Nachtsheim C, Holzgrabe U, Borsodi A (2003) Kappa-receptor selective binding of opioid ligands with a heterocyclic bicyclo[3.3.1]nonan-9-one structure. Acta Biol Hung 54 147-155... 

Significant progress in conformational studies of bicyclo [3.3.1] nonanes in the past two decades have revealed the main conformational features of carbocyclic compounds bearing different substituents, including the ways in which both chair-boat and boat-boat conformations could be stabilized. The conformational behavior of some heterobicyclo[3.3.1]nonanes was interpreted in terms of conformational effects (8). Naturally occurring compounds that include the bicyclo[3.3.1]nonane moiety in their structure have also been studied extensively (9-15). 

In the present chapter, the basic principles of the conformational analysis of substituted bicyclo[3.3.1]nonanes and their hetero analogs are considered. These principles are illustrated with experimental and computational data with attention concentrated on those results believed most important to the understanding of the conformational behavior of bicyclo[3.3.1] nonanes. Some results previously reviewed in references 1 and 2 are not discussed here. Conformational studies of polycyclic compounds that incorporate the bicyclo [3.3.1] nonane skeleton as part of their structure are generally beyond the scope of this chapter. 

The conformational analysis of bicyclo[3.3.1]nonanes continues to develop. Despite the publication of a great many experimental and calculational results, as evidenced in this chapter, at present, the conformational behavior of many comparatively simple structures has not yet been investigated. 

The predominant conformation of the mother compound bicyclo[3.3.1]nonane in the gas phase is the double chair (cc), as detected by electron diffraction studies (120-123). The most important destabilization in the cc conformer of this structure is van der Waals repulsion of the endo-3- and endo-7- hydrogen atoms. In the twin-chair conformation with ideal tetrahedral angles, the C3-C7 separation would be 2.5 A and the separation of the corresponding endo-hydrogen atoms would have the physically impossible value of 0.75 A (124). Repulsion induces an elongation of the C3- - C7 distance to 3.1 A, which translates to an endo-hydrogen distance of 2.2 A,... 

Initially the main PBDs isolated from floral resins of Clusia spp. showed to be bicyclo-[3.3.1]-nonane derivatives but a new study demonstrated the presence of several SBDs in these sources. Structures of weddellianone A (24) and B (25), lanceolatone (26) and hilarianone (27) were established on spectroscopic evidences of their methyl derivatives obtained after treatment of fresh floral resins with diazomethane [20], All the structures were represented with a 1,3,5-triketone system because of the treatment before mentioned don t facilitate the determination of the exact structures. On the other hand, many natural SBDs have shown to have methoxyl groups in their structures and then in the methyl derivatives above mentioned is not possible to establish the origin of the methoxyl groups certainly. 

As xanthochymol, many PBDs isolated from Guttiferae show a structure based on the bicyclo-[3.3.1]-nonane-2,4,9-trione system (Table 2). 

We proposed to group PBDs that present a bicyclo-[3.3.1]-nonane-2,4,9-trione system in accord with benzoyl moiety position type A if it is on C-l, type B if it is on C-3 and finally type C if it is on C-5, Fig.(5) [40]. The structures previously reported as type C, nemorosone and 7-epinemorosone, have been corrected and all polyisoprenylated benzophenones derivatives with a bicyclo-[3.3.1]-nonane-2,4,9-trione system isolated, therefore, are derivatives of type A or B [18,19]. 

The boron atoms of the bicyclo[3.3.1]nonane-like6-structured bis[ju-(2,2-... 

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