Nine- and Ten-membered Rings

Nine- and Ten-membered Rings.—Two conformation exchange processes have been detected by n.m.r. for 4,4,7,7-tetramethylcyclononanone, which was assigned the asymmetric [2,3,4] conformation (19), with the carbonyl group in a non-corner position.  

Conformational behaviour of several cyclonona-l,3,6-trienes has been studied by variable-temperature H n.m.r. The geminal methyl groups of 9,9- and 8,8-dimethyl-cyclonona-l,3,6-triene were found to be equivalent near 0°C owing to conformational flipping, and conformations (20 = Me, = H) and (20 R = R = H, 

R = Me), respectively, were suggested on the basis of chemical shift data. 5,9,9-Trimethylcyclonona-l,3,6-triene adopts conformation (20 R = R = Me, R = H) at low temperatures.  

The variable-temperature H n.m.r. spectrum of 4,4,8,8-tetramethylcyclodecanone has been interpreted in terms of a boat-chair-chair conformation.  

The cyclodecanone ring of ( )-3P-hydroxy-5,10-seco-l(10)-cholesten-5-one was shown to adopt an extended crown conformation by an A -ray structure determination of its p-bromobenzoate. In contrast, analysis of the and n.m.r. spectra of its acetate showed two conformations to be present in solution, the major one (85%) corresponding to the extended crown observed in the solid state, and the minor one corresponding to conformation (23). The failure of force-field calculations to reproduce the energy differences between different conformations was attributed to a transannular interaction between the double bond and the carbonyl group. The observed conformations were used to rationalize the stereochemistry of several reactions of these seco-steroids.  

Nine- and Ten-membered Rings.—Conformational energies and interconversion barriers have been calculated for cyclononane. The [3,3,3]-conformation was found to be the most stable. N.m.r. indicated that cyclonona-l,2,6-triene adopts the unsymmetrical twist-boat-chair conformation (19) and undergoes a hindered pseudorotation with an activation energy of 12.9 kcal mol to achieve C2 time-averaged symmetry.  

Steric energies of nine conformations of cis,cis-, trans,trans-, and cis,trans-cyclo-deca-1,6-diene have been calculated using an extended force-field method. The minimum energy conformation for the trans,trans-isomeT was found to be (20).  

Larger Rings.—The crystal structures of two substituted bertya-5,12-diene-3,14-diones (25 X = H, OH) and of 1,1-dihydroperoxycyclododecane (at —160 have been reported. The conformation of the methyl acetal of kansuinine A (26) has been studied using NOE measurements/ and the structure of a derivative of the related kansuinine B has been determined by an X-ray analysis.  

A regular diamond lattice conformation was found for cyclotetradecanone at —157 °C. The structures of sinulariolide (27) and a plant-growth inhibitor found to be 4,8,13-duvatriene-l,3,-diol(28) have been confirmed using X-ray methods. 

spectrum of [1- C cyclqhexadecane shows three resonances, in the ratio of 1 2 1, at —152 °C, assigned to the [4,4,4,4] conformation (29). This is in agreement with iterative strain energy calculations which indicated that the [4,4,4,4] 

Three interesting papers report the preparation and structural elucidation by m.s. of 6,ll,12,13-tetrahydro-5/f-dibenz[6, ]azonine-6,13-diones (435) and 

Katsuura, K. Mochinaga, and M. Ezaki, Chem. and Pharm. Bull. Japan), 1972, 20, 76. 

or ZnBr) ii, Mel iii, NaNHj or NaOEt iv, N2H4-KOH. 

Decahydroazecines (454) and (455) are described, and the reaction of tetrasulphur tetranitride with norbomene has been shown to yield the exo-cis structure (456), elucidated by i.r., n.m.r., and u.v. studies. Compounds (457) and (458) are other ten-membered ring heterocyclic structures described this year.  

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In analogy to Edstrom s experiments, the nine- and ten- membered ring lactams underwent regio and stereoselective transannular ring contractions to give the corresponding indolizidinones and quinolizidinones, respectively (vide supra Scheme 56) (Table 21) [61]. 

The six- and seven-membered rings S5NR and S6NR are yellow oils that exhibit molecular ions in their electron-impact mass spectra. The nine- and ten-membered rings S8NH and S9NH form photosensitive, pale yellow crystals that are soluble in CS2. The 12-membered ring SnNH has only been characterized by spectroscopic methods.207... 

While the reaction of ketones with hydrogen peroxide yields only six- and nine-membered ring peroxides, other peroxidic ring structures are formed from aldehydes. From formaldehyde and hydrogen peroxide, for example, Rieche and Meister35 obtained cyclic peroxides with seven-, nine-, and ten-membered rings. 

Nine- and Ten-membered Rings.—Ring-forming Reactions. Treatment of transjrans-farnesyl phenyl sulphide with N-bromosuccinimide and sodium carbonate gave mon-epoxide (58), which cyclized on treatment with n-butyl-lithium and DABCO to give a mixture of (59 R = SPh) and its 2,3-cis-double bond isomer (total yield of 60%). Removal of the phenylthio-group by lithium-ethylamine reduction gave a mixture of (59 R = H) and (60). ... 

Nine- and Ten-membered Rings.—Direct irradiation of cw-cyclononene in the vapour phase gives a mixture of nona-1,8-diene and vinylcycloheptane, whereas sensitized irradiation gives a mixture of nona-1,8-diene and five bicyclononanes. Metathesis of cis,cis-cyclonona-l,5-diene over a WCl -LiAlH catalyst gives a mixture of polymer (75%), starting material, cyclopentene, c/s-l,2-divinylcyclopentane, and an... 

Nine- and Ten-membered Rings.—Reduction of 1-bromo-cw-cyclononene and either l-bromo-trans,ds- or l-bromo-ds,cis-cyclonona-l,5-diene with sodium in liquid ammonia gave ds-cyclononene and cis,ds-cyclonona-1,5-diene, respectively." Thermolysis of bicyclo[7,l,0]deca-l,7-diene and bicyclo[8,l,0]undeca-1,8-diene gives 3-methylene-cis,ds-cyclonona-l,4-diene and a mixture of 3-methylene-ds,ds-cyclo-deca-1,4-diene and 10-methylenebicyclo[5,3,0]dec-8-ene, respectively. Cyclo-nonanone tosylhydrazone gives ds-cyclononene exclusively when treated with methyl or n-butyl lithium, whereas both cis- and trans-cyclodecenes are obtained from cyclo-decanone tosylhydrazone. The cis.trans olefin ratio in this case is solvent dependent probably, because of the effect of solvent on the tosylhydrazone conformation." ... 

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