294-41-7

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Cycloundecane (1) was shown to exist at -183.1 °C as a mixture of the [12323] (～59%) and [335] (～41%) conformations. Populations were determined from the 13C NMR spectrum, and assignments were based on the 13C spectra, calculated free energies and chemical shifts, and information from the literature, including X-ray studies of solid derivatives and calculated barriers.

The volumes of reaction determined for the hypothetical cyclization of 1-alkenes to cycloalkanes decrease continUOusly from the formation of cyclopropane (ΔV(R) = -5.5 cm3 mol-1) up to the formation of cyclodecane (ΔV(R) = -32.3 cm3 mol-1) and seem to be constant for the larger rings. The analysis of the packing coefficients (η = V(w)/V) leads to the conclusion that this ring-size dependent decrease in volume results from the different packing of cyclic and acyclic compounds rather than from the changes in their intrinsic molecular volumes. The investigation of the intramolecular Diels-Alder reactions of (E)-l,3,8-nonatriene (E)-1 and (E)- 1,3,9-decatriene (E)-2 leading to the bicyclo[4.3.0]nonenes cis- and trans-4 (ΔV≠/ΔV(R) [cm3 mol-1] -24.8/-32.0 and -24.8/-28.5, respectively) or bicyclo[4.4.0]decenes cis- and trans-6 (-37.6/-45.4 and -35.0/-37.4, respectively) confirms the ring-size dependence of the activation and reaction volumes. The dependence of the effect of pressure from the number of newly forming rings is illustrated with the thermolysis of (Z)-1,3,8- nonatriene (Z)-1 in which an intramolecular Diels-Alder reaction leading to bicyclo [4.3.0]nonene cis-4 competes with a sigmatropic [1,5] hydrogen shift leading to (E,Z)-1,5,7-nonatriene 7. The use of high pressure causes a reversal of selectivity.

A study of rhodium(I)-catalyzed synthetic transformations involving selective breaking of the C-C bond α to the carbonyl group of cyclobutanones is described. Decarbonylation took place on treatment of a cyclobutanone with an equimolar amount of (Ph3

The known ketone 4, the new paracyclophane ketones 6, 7, and 9-12 and the known hydrocarbons 5, 8, and 13 are obtained by successive thermal extrusion of carbon monoxide from the n>paracyclophane(ones)n 1, 2, and 3 (n=2,3,4).The X-ray structure analyses of the 20-membered 6 and the 26-membered ring 10 are reported. Key Words: Cyclophanes / Decarbonylation / Paracyclophanes / Pyrolysis / Ketone pyrolysis, selective

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Reactions of C5-C12 cycloalkyl radicals and carbenes produced during radiolysis, vacuum-u.v. photolysis, and decomposition of cycloalkanone p-tosylhydrazones were investigated.The disproportionation to combination ratios of radicals are ca. 1 and agree with the ratios of linear secondary radicals.The disproportionation smaller cycloalkyl radicals yields cis-cycloalkenes and cycloalkanes; from C9 and C10 cis- and trans-cycloalkenes and cycloalkanes and from C11 and C12 trans-cycloalkenes and cycloalkanes are produced.Both atoms of H2 given off in the elimination reaction from excited cycloalkane molecules orginate from the same carbon atom and in this process carbenes are formed.Rearrangement of small (C5, C6) and large (C11, C12) cycloalkylcarbenes in the solvent of the given cycloalkane occurs by 1,2-hydrogen migration.C7-C10 carbenes rearrange both by hydrogen atom migration and transannular insertion.

The photochemistry of a series of simple trans-fused bicyclo 2,4-dienes (n=3, 4, 5) which possess semirigid structures in the ground state has been studied. trans-Bicyclonona-2,4-diene gave rise to cis,cis,cis-cyclonona-1,3,5-triene, the first example of a nonaccordant cyclohexadiene ring opening.The trans-bicyclodeca-2,4-diene at -40 deg C, using 254-nm light, yielded trans,cis,trans-cyclodeca-1,3,5-triene.This triene upon further irradiation yielded endo,endo-tricyclo2,10>dec-8-ene.The triene was extremely thermally labile and was readily converted to cis-bicyclodeca-2,4-diene.At -78 deg C, the photostationary state of trans-bicyclodeca-2,4-diene showed a wavelenght dependency.The photochemistry of trans-bicycloundeca-8,10-diene was analogous to that of the ten-carbon analogue.