Crystal and molecular structure of the tetrachloropalladate of the dication meso-3,7-diazonia tricyclo[4.2.2.22,5]dodeca-3,7,9,11-tetraen-4,8 diamine obtained by coupling reaction of 2-aminopyridines

A solution of trans-bis(2-aminopyridine)dichloropalladium(II) in DMF and HCl 2 N was left for several weeks. The compound isolated from this solution was identified by X-ray structural analysis as the tetrachloropalladate of meso-3,7-diazonia tricyclo[4.2.2.2^2,5] dodeca-3,7,9,11-tetraen-4,8 diamine, which contains a dication not previously described in literature. The organic dication is formed by two aminopyridine rings linked by CC bonds whose length is greater (1.61 Å) than a normal single CC bond.     

C12H12 interconversions: Two non-pyrolytic syntheses of tricyclo[5.3.2.04,8]dodeca-2,5,9,11-tetraene

Herein, we describe two independent and non-pyrolytic syntheses of an important C₁₂H₁₂ hydrocarbon which had been prepared previously by gas phase thermolysis of compound 6. The first method is based on an unusual dipolar cycloaddition of dichloroketene onto bullvalene. After reductive dechlorination, a Shapiro-Heath reaction of the tosylhydrazone gave the title compound. Alternatively, compound 13 is also obtained from its isomer 6 by a Ag⁺ catalyzed reaction.     

Enantiospecific synthesis of tricyclo[5.2.1.0]decanes via acid catalysed rearrangement of isotwistanes

An acid catalysed rearrangement was employed for the enantiospecific conversion of isotwistanol to tricyclo[5.2.1.0^4,8]decanes, which provided support for the proposed biosynthesis of allopupukeananes from pupukeananes. The strategy has been further extended to the enantiospecific synthesis of a homobrexane.     

Synthesis and rearrangement of [1,1′-bicyclobutyl]-1-ols and spiro[3.4]octan-5-ols: a general access to bicyclo[3.3.0]octenes (hexahydropentalenes)

Several new Grignard reagents based on substituted cyclobutanes have been generated and added to cyclobutanones to yield mono- to trimethylated [1,1′-bicyclobutyl]-1-ols. Mono- to trimethylated spiro[3.4]octan-5-ols have been prepared from the parent ketone via alkylation and/or addition reactions. Upon treatment with acid, all [1,1′-bicyclobutyl]-1-ols and spiro[3.4]octan-5-ols rearrange to yield a single bicyclo[3.3.0]octene.     

Density functional study of tricyclo[3,3,1,13,7]decane and tricyclo[3,3,1,13,7]decsilane and their halogen derivatives

The B3LYP/3‐21G* ab initio molecular orbital method from the Gaussian 94 computer program package was applied to study tricyclo[3,3,1,1^3,7]decane and tricyclo[3,3,1,1^3,7]decsilane molecules and their halogen derivatives (1,3,5,7‐tetrahalotricyclo[3,3,1,1^3,7]decane and 1,3,5,7‐tetrahalotricyclo[3,3,1,1^3,7]decsilane, C₁₀H₁₂X₄, and Si₁₀H₁₂X₄). The optimized structures of these compounds were obtained. Ionization potentials, HOMO and LUMO energies, energy gaps, heats of formation, atomization energies, and vibration frequencies were calculated. These calculations indicate that these molecules are stable and have T_d symmetry. Tricyclo[3,3,1,1^3,7]decsilane and its halogen derivatives (Si₁₀H₁₂X₄) are found to have higher conductivity than that of tricyclo[3,3,1,1^3,7]decane and its halogen derivatives (C₁₀H₁₂X₄). 1,3,5,7‐Tetraflourotricyclo[3,3,1,1^3,7]decane (C₁₀H₁₂F₄) and 1,3,5,7‐tetraflourotricyclo[3,3,1,1^3,7]decsilane (Si₁₀H₁₂F₄) were found to be the easiest compounds to form and the most difficult to dissociate of all 1,3,5,7‐tetrahalotricyclo[3,3,1,1^3,7]decane and 1,3,5,7‐tetrahalotricyclo[3,3,1,1^3,7]decsilane compounds, respectively. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 72: 189–198, 1999     

Structure, strain, and degenerate rearrangement of tricyclo[2.1.0.0 1,3]pentasilane and related molecules

We theoretically investigate a highly strained tricyclic silane (tricyclo[2.1.0.0 1,3]pentasilane (4b), an isomer of pentasila[1.1.1]propellane (3b)) composed of three fused three-membered rings. The central ring is distorted. One of the fusion bonds in the central ring is shorter than the normal Si-Si single bond (2.350 A) whereas the other is as long as the fusion bonds in bicyclo[1.1.0]tetrasilane (2b) (2.860 A) and 3b (2.778 A). The tricyclic silane is less strained than the carbon congener and more strained than the isomer 3b. The electron delocalization between one of the fusion bonds and the geminal Si-Si ring bonds elongates the fusion bond and stabilizes the molecules to reduce the strain. The silanes composed of the fused three-membered rings are less strained than the carbon congener. A degenerate rearrangement of a three-membered ring is predicted. The enthalpy of activation of the rearrangement of the distorted central ring is low (7.2 kcal/mol) for 4b, but appreciable (22.3 kcal/mol) for the germanium congener, tricyclo[2.1.0.0(1,3)]pentagermane (4c). We investigate the effects of the substituents on the distortion of the central three-membered ring and the degenerate rearrangement.     

Diels-Alder reactions of highly pyramidalized tricyclo[3.3.0.0]oct-1(5)-ene derivatives: further chemistry of pentacyclo[6.4.0.0.0.0]dodeca-5,8,11-triene

A study of the trapping of highly pyramidalized tricyclo[3.3.0.0^3,7]oct-1(5)-ene derivatives (generated from a 1,2-diiodo precursor on reaction with t-BuLi, 0.45% sodium amalgam and molten sodium) with different dienes (11,12-dimethylene-9,10-dihydro-9,10-ethanoanthracene, 1,3-diphenylisobenzofuran, 2,5-dimethylfuran and furan) is presented. Byproducts from the trapping of pentacyclo[6.4.0.0^2,10.0^3,7.0^4,9]dodeca-5,8,11-triene with 1,3-diphenylisobenzofuran have been synthesized and fully characterized, including an X-ray diffraction analysis. Also, the above triene has been cross coupled with 3,7-dimethyltricyclo[3.3.0.0^3,7]oct-1(5)ene to give a tetrasecododecahedratetraene derivative.     

Helical primary structures of 1,3-spiroannelated five-membered rings: (±)-trispiro[4.1.1.4.2.2]heptadecane and (±)-tetraspiro[4.1.1.1.4.2.2.2]heneicosane

A combination of three spiroannelation methods forms the basis for a synthesis of the first two helical hydrocarbons of 1,3-spiroannelated five-membered rings.     

Synthesis, structural characterization, and skeletal rearrangement of dibenzo tricyclo[3.3.0.0]-1,2,5,6-tetrasubstituted octanes

Dibenzo tricyclo[3.3.0.0^2,6]-1,2,5,6-tetrasubstituted octanes, the ‘twisted’ highly strained valence isomers of substituted dibenzo[a,e]cyclooctatetraenes, were synthesized and their structure characterized by single-crystal X-ray analysis. Their skeletal rearrangement was experimentally observed.     

Aromatics to polyquinanes: A general method for the construction of tricyclo[6.3.0.0]-and tricyclo[6.3.0.0]undecanes

The conversion of aromatic compounds to linear and angular triquinanes is described and involves a 5-exo-trig-allyl radical cyclization as the key reaction for constructing the strained ketones 9 and 18, which are then transformed into the quinanes 12 and 23, respectively.     

Synthesis of tricyclo[6.2.2.0]dpdecane and tricyclo[6.3.1.0]dodecane ring systems involving intramolecular cyclisation of diazomethyl ketones

2,8-Dimethyltricyclo[6.2.2.0^1,6]dodeca-2,5-diene-4,9-dione ( ), 2,9-dimethyltricyclo [6.3.1.0^1,6]dodeca-2,5-diene-4,10-dione ( ) and 2-methyltricyclo[6.3.1.0^1,6]dodeca-2,5-diene-4,10-dione ( ) have been synthesised for entry into the ring systems of a few tetracyclic diterpenes.     

Photochemistry of some steroidal bicyclo[3.1.0]hexenones

The photochemistry of five 11-hydroxy-1,5-cyclopregn-3-en-2-ones (‘lumi’ products from the corresponding pregna-1,4-dien-3-ones) has been investigated. In all cases the photoproducts were 1,11-oxy derivatives, resulting from intramolecular attack of the hydroxyl group to the incipient positive charge at C-1. When a fluorine atom was present at C-6, HF elimination took place concurrently with the nucleophilic addition and led to linearly conjugated dienones, rather than the enones obtained in the other cases. Quantum yields were in the range 0.06-0.2, the lower values applying when a fluorine atom was present in position 6 (not in position 9). The results add new evidence on the role of zwitterionic intermediates in the photochemistry of cross-conjugated dienones and the corresponding lumi photoproducts.     

A synthesis of the tricyclo[6.3.0.0]undecane system.

A short and efficient synthetic route to the tricyclo[6.3.0.0^2,6]undecane ring system is described; the key steps are photochemical annelation of an enolized β-diketone to produce a 1,5-diketone (the de Mayo reaction) followed by intramolecular reductive coupling using a low valence titanium species (McMurry's reagent).     

Drastic change in the rate of photochemical rearrangement of 1,6-(N-phenyl)aza-[60]fulleroids by switching the excited states through simple methyl substitution on the phenyl group

The reaction rate for the photochemical rearrangement of 1,6-N-(substituted-phenyl)aza-[60]fulleroid 1 to 1,2-N-(substituted-phenyl)aziridino-[60]fullerene 2 differed ca. 3000-fold depending on the position and number of methyl substituents on the N-phenyl group. The required time for the completion of the reaction decreased in the order 2,6-dimethylphenyl (1d) < 2-methylphenyl (1b) < phenyl (1a) < 4-methylphenyl (1c). The difference was mainly due to switching of the excited states between normal (fast reactions) and charge-separated (slow reactions) triplet states, which was induced by steric interactions between the N-phenyl group and the C₆₀ moiety.     

Reaction products of methyl tricyclo[4.1.0.02,7]heptane-1-carboxylate and tricyclo[4.1.0.02,7]hept-1-yl phenyl sulfone with dinitrogen tetraoxide

The reaction of methyl tricyclo[4.1.0.0^2,7]hepatne-1-carboxylate with dinitrogen tetraoxide in diethyl ether at ?10 to 0°C, followed by treatment of the reaction mixture with methanol, gave approximately equal amounts of methyl exo,syn-6,7-dinitro-and exo-6-hydroxy-syn-7-nitrobicyclo[3.1.1]heptane-endo-6-carboxylates. Tricyclo[4.1.0.0^2,7]hept-1-yl phenyl sulfone reacted with dinitrogen tetraoxide under analogous conditions to produce a mixture of diastereoisomeric exo,syn-and endo,syn-6,7-dinitro-6-phenylsulfonylbicyclo-[3.1.1]heptanes and 6,6-dimethoxy-endo-7-nitrobicyclo[3.1.1]heptane at a ratio of 4.5:2:1. Probable factors responsible for the different stereoselectivities in the addition of N₂O₄ at the central C¹-C⁷ bond of the initial tricycloheptane compounds were discussed. The structural parameters of the dinitro ester and related dinitro sulfone were compared on the basis of the X-ray diffraction data.     

Trifluoromethanesulfonylimides of arenehydroxamic acids and their aza Lossen rearrangement

Trifluoromethanesulfonylimides of arenehydroxamic acids ArC(NSO₂CF₃)NHOH (1), analogues of arenehydroxamic acids, in which sp² hybridized oxygen atom is replaced by the much stronger electron-withdrawing group NSO₂CF₃, have been synthesized, and the abilities of these compounds to undergo transformations similar to the Lossen rearrangement have been studied.At heating O-trimethylsilyl or O-tosyl derivatives of acids 1 rearrange to carbodiimides ArNCNSO₂CF₃ or products of their hydration, the corresponding carbamides. Interaction of acids 1 with sulfinyl chloride or phosphorus pentachloride results in formation of N-trifluoromethylsulfonyl-N′-arenechloroformamidines, ArNHC(Cl)NSO₂CF₃, which were transformed into their morpholine derivatives and thus characterized.     

Gas chromatographic behaviour of isomeric tricyclo[10.4.0.04,9]hexadecanes

Summary Using achiral stationary phases of different polarity in capillary gas chromatography it is demonstrated that the hydration of 1,2–5,6-dibenzocycloocta-1,5-diene yields five isomers of the tricyclo[10.4.0.0^4,9]hexadecanes. With highly polar stationary phases all isomers of the tricyclic hexadecanes and the semihydrated products in the mixture were also separated from each other. The chiral isomers were separated on cyclodextrin stationary phase. Moreover, with columns of achiral and chiral phases coupled in series, in a double oven gas chromatograph, it was possible to estimate the configuration of the isomers. The separation of diastereomers on chiral stationary phases is a useful means for structural assignment of isomeric compounds.Dedicated to Professor Leslie S. Ettre on the occasion of his 70th birthday.