Bicyclo nonane system

Nucleophilic attack occurs at C(2) of the diene. The 1,3-cyclohexadiene complex 66 is converted to the homoallyl anionic complex 67 by nucleophilic attack, and the 3-alkyl-1-cyclohexene 68 is obtained by protonation. Insertion of CO to 67 generates the acyl complex 69, and its protonation and reductive elimination afford the aldehyde 70 [20]. Reaction of the butadiene complex 56 with an anion derived from ester 71 under CO atmosphere generates the homoallyl complex 72 and then the acyl complex 73 by CO insertion. The cyclopentanone complex 74 is formed by intramolecular insertion of alkene, and the 3-substituted cyclopentanone 75 is obtained by reductive elimination. The intramolecular version, when applied to the 1,3-cyclohexadiene complex 76 bearing an ester chain at C(5), offers a good synthetic route to the bicyclo[3.3.1]nonane system 78 via intermediate 77 [21]. 

Another type of carbopalladation is observed in the oxidation of the 2,2-disubstituted alkene attached to the cyclobutanol 104. The shift of the carbon-carbon bond as shown by 105 and ring expansion generate 106. Intramolecular alkene insertion gives the bicyclo[4.3.0]nonane system 107. Finally, 108 is obtained [78],... 

Bicyclic carbosilanes are more difficult to synthesize than compounds of the (me2Si-CH2) type, partly owing to differences in the reactivity of the functional intermediates caused by effects of the substituents. So far synthesis of the l,3,5,7-tetrasila-bicyclo-[3.3.1]nonane system and of the 1,3,5,7,9-penta-siladecaline system has been reported (16). 

Extension of the TMM strategy to intramolecular reactions greatly expands the scope of this BCR methodology. The precursors are readily available, e.g. from the silyl Grignard reagent (123) and w-oxo-a,p-unsaturated substrates (equation 126). Ester- and sulfonyl-substituted bicyclo[3.3.0 octane and bicy-clo[4.3.0]nonane systems are readily constructed in a single step from acyclic material (equations 127, 128). ... 

III. Conformational Analysis of Carbocyclic Bicyclo[3.3.1]nonane Systems Experimental and Computational Data... 

III. CONFORMATIONAL ANALYSIS OF CARBOCYCLIC BICYCLO[3.3.1]NONANE SYSTEMS EXPERIMENTAL AND COMPUTATIONAL DATA... 

An interesting example of a reaction involving conformational equilibria in 3,7,9-substituted bicyclo[3.3.1]nonane systems is the base-induced rearrangement of endo-7,7-dimethylbicyclo[3.3.1]nonan-3-ol-9-one (80) into 81. The rearrangement is rationalized by a reversible intramolecular transfer of hydride from the carbinol methine to the carbonyl carbon (60). The reacting centers at C-3 and C-9 are only placed in proximity when the cyclohexanol ring adopts a boat conformation. The resulting ketol 81 is 2.7 kcal mol 1 more stable than its isomer 80 (60). 

In bis compounds 256, 256+, and 257 (9-borabicyclononane, BBN), the bicyclo[3.3.1]nonane system adopts a chair-chair conformation according to X-ray studies (195,196). The CC conformation was also found for some other BBN derivatives (197-199). 

The data considered here demonstrate that, despite occasionally unusual conformational behavior, the preferred conformation of the bicyclo[3.3.1]nonane system can be predicted following the analysis of intramolecular interactions and a comparison with the conformational behavior of molecules already described. In many cases, the preferred... 

Moreover, these conformational regularities are important in the study of reaction mechanisms, including intramolecular migrations, rearrangements, and solvolyses of bicyclo[3.3.1]nonane systems (e.g., see references 60,250, and 251). 

The bicyclo[3.3.1]nonane system found in rings B and D of lycopodine has been used by two groups in efforts to arrive at the lycopodine system. In the work of Colvin et al. (55) the readily available bicyclo-... 

Four isolated PPBs, with the bicyclo[3.3.1]nonane system, contain peroxide bonds 15,16-dihydro-16-hydroperoxyisoplukenetione F (108), ochrocarpinone A (111), plukenetione C (113), and 33-hydroperoxyisoplukenetione C (123) [66,78]. 

The l3C, DEPT-135, and DEPT-90 experiments showed a nonconjugated ketone at 5 209.8, flanked by two quaternary bridgehead carbons (5 59.5 and 68.9), an enolized 1,3-diketone [5 117.9 and 194.5 (2x)], a methylene carbon at 5 42.7, and a methine carbon at 5 47.0 which, together with a quaternary carbon at 5 50.4, established the bicyclo[3.3.1]nonane system in xanthochymol (138). The DEPT-135 showed five sp2 methines and six aliphatic methylenes. The number of methine carbons, five sp2 and two aliphatic, was confirmed by a DEPT-90 experiment. The carbon and DEPT experiments further indirectly confirmed the AMX 3-spin system with l3C quaternary aromatic resonances at 5 128.7, 145.3, and 151.4, and the number of prenyl groups as four (two isopent-2-enyl and two isopent-3-enyl groups). 

C-5 (5 50.4) confirmed the bicyclo[3.3.1]nonane system, Fig. (7B) and iii) the geminal-dimethyl protons which displayed HMBC cross peaks to each other, Fig. (7C) iv) HMBC cross peaks from the methyl groups to the olefinic carbons and correlations from the CH2 groups to their respective olefinic carbons confirmed the two isopent-2-enyl groups, Fig. (7D) and v) HMBC cross peaks from H-29 (5 2.0) to C-30 (5 43.7) and C-31 (5 147.9), from H-35 (5 1.9) to C-34 (5 32.1), C-30 (5... 

When the target bicycle lacks a suitably placed double bond in a six-membered ring, retrosynthesis starts with FGA (= add double bond) [95, 96, 97, 98]. In bicyclization reactions forming an endoendo bond, the stereochemistry of the reaction has to be monitored (formation of a cis or of a trans fusion of the two rings). With anellated systems of a five- to a six-membered ring the cis juncture is thermodynamically favored. This renders it possible to reach a cis fused bicyclo[4.3.0]nonane system by an epimerization process following the bicyclization reaction [99] (Scheme 6.25). 

The same problem occurs with the bicyclo[3.3.1]nonane system when there is an endo substituent at both C-3 and at C-7 resulting in a double twist boat conformation. Since each of the model, monosubstituted compounds will be predominately in a boat - chair arrangement, they will not serve as good sources for A6 effects for the disubstituted system and their use results in sizable orors for C-3 and C-7. 

The intermediates in the production of (140) were isolated when the formation of ring A was carried out under mild conditions (without boiling with sodium methoxide) which led through the diketone (139) to the epim-eric ketols (141). Rings A and B of these compounds form a bicyclo-[3,3,1]-nonane system [57] originally, these products were assigned the structure of compounds (142) epimeric at C5 with the decalin system of rings A and B [56]. The ratio of the isomers of ketol (141) formed depends on the reaction conditions and, in the first place, on the concentra-... 

Various bicyclic and polycyclic compounds are produced by intramolecular reactions] 127]. In the syntheses of the decalin systems 157 [38] and 158 [128], cis ring Junctions are selectively generated. In the formation of 158, allyhc silyl ether remains intact. A bridged bicyclo[3.3. l]nonane ring 159 was constructed... 

Bridged systems can also be prepared in high yield by this process.84 For example, treatment of the keto diester (348 Scheme 43) with (61) in basic DMSO gave a 41% yield of the diketo diester (352) by way of the intermediates (349) to (351), involving two Michael additions and final Dieckmann condensation.84 Similar processes have also been used to make other bicyclo[3.3.1]nonanes and related com-... 

However, in a reaction similar to (26), the bicyclic system shown in reaction (27) is formed and the 1,3,3,5,7-pentamethyl-7-monochloro-l,3,5,7-tetrasila-bicyclo-[3.3.1]-nonane is obtained. 

In the case of McycKc systems (133—140) there are not yet enough data available for a detailed discussion to be given. The barriers obtained for the bicyclo [2.2.2]octane (133, 134) and the bicyclo[3.3.1]nonane (139, 140) compounds are in the range expected for the corresponding mono-cyclic systems. In the case of the bicyclo[3.2.2]nonane derivatives 135 and 136 the inversion barriers are larger than in the seven-membered ring compounds 127 and 128. 

Although alkali metal-NHs reductions are usually preferable to Na-alcohol reductions in terms of yield and convenience, the stereochemical consequences of both systems are similar, at least for all sterically hindered systems studied thus far. Illustrative examples are the reductions of bicyclo[3.3.1 ]nonan-ones (35 equation 14) and (36 equation 15). ° In both cases the equatorial alcohols (37) and (38) were obtained in excellent yield and with complete stereoselectivity. LAH reduction of ketone (35) gave only the epimeric axial alcohol, while (36) gave a mixture of (38) and its epimer. ... 

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