Polyesters containing bicyclo[2.2.2]octane and bicyclo[3.2.2]nonane rings

Polyesters containing bicyclo[2.2.2]octane and bicyclo[3.2.2]nonane rings are prepared from 1,4-bis(carboethoxy)bicyclo[2.2.2]octane, 1,4-bis(hydroxymethyl)bicyclo[2.2.2]-octane and the 1,5-disubstituted bicyclo[3.2.2]nonane analogs. These polyesters are compared to the related polymers containing 1,4-phenylene and trans-1,4-cyclohexylene rings in terms of their melting point, thermal stabilities and oxidative stabilities. The lower symmetry of the bicyclo[3.2.2]nonane ring produces lower-melting polymers than the other ring systems. The remaining three rings are approximately equivalent in their effect on the melting point of a polymer provided that no more than one bicyclo[2.2.2]octane ring is present per polymer repeat unit. Two such rings produce a highermelting polymer than any other combination. Both the thermal and oxidative stabilities of the polyesters is improved by the presence of the bicyclo rings. This is attributed to the rings providing an approximation of a ladder polymer.     

The electronic structure of bicyclo [2.2.1] heptane and of bicyclo [2.2.2] octane

An ab initia SCF-LCAO-MO study of bicyclo [2.2.1] heptane(I) and of bicyclo [2.2.2] octane(II) has been performed. The electronic structure and the nature of the molecular orbitals and of the bonds have been analyzed. Interactions between fragment orbitals may be recognized. The bridgehead C-H bonds interact dominantly “through-space” in I and “through-bond” in II. Some relations between electronic structure and molecular properties are discussed.     

Asymmetric addition of pyridine to 1,4-bis(ethynyl)bicyclo[2.2.2]octane: dissymmetrical rotator ligands illustrated in dpppPt(II) and [Re6Se8]2+ complexes and an amphidynamic hydrogen bonded framework solid

A polar function like pyridine increases the polarity difference between mono- and disubstituted 1,4-bis(trimethylsilylethynyl)bicyclo[2.2.2]octane cores allowing for their ready separation by chromatography, affording two dissymmetrical ligands illustrated in metal-rotor hybrids like a corner-shaped mononuclear complex, an octahedral hexanuclear metal complex, and a framework solid with a rather slow rotator.     

Unexpectedly similar charge transfer rates through benzo-annulated bicyclo[2.2.2]octanes

A 4-(pyrrolidin-1-yl)phenyl electron donor and 10-cyanoanthracen-9-yl electron acceptor are attached via alkyne linkages to the bridgehead carbon atoms of bicyclo[2.2.2]octane and all three benzo-annulated bicyclo[2.2.2]octanes. The sigma-system of bicyclo[2.2.2]octane provides a scaffold having nearly constant bridge geometry on which to append multiple, weakly interacting benzo pi-bridges, so that the effect of incrementally increasing numbers of pi-bridges on electron transfer rates can be studied. Surprisingly, photoinduced charge transfer rates measured by transient absorption spectroscopy in toluene show no benefit from increasing the number of bridge pi-systems, suggesting dominant transport through the sigma-system. Even more surprisingly, the significant changes in hybridization undergone by the sigma-system as a result of benzo-annulation also appear to have no effect on the charge transfer rates. Natural Bond Orbital analysis is applied to both sigma- and pi-communication pathways. The transient absorption spectra obtained in 2-methyltetrahydrofuran (MTHF) show small differences between the benzo-annulated molecules that are attributed to changes in solvation. All charge transfer rates increase significantly upon cooling the MTHF solutions to their glassy state. This behavior is rationalized using combined molecular dynamics/electronic structure trajectories.     

Determination de la configuration absolue de quelques derives du bicyclo[2.2.2]octane: Utilisation comparee de la regle des octants et de la methode d'horeau

A series of bicyclo[2.2.2]octane derivatives whose absolute configurations are known through chemical correlations with confirmed reference products (bicyclo[2.2.2]octanol, bicyclo[2.2.2]octene carboxylic acid) have been prepared.     

Terminal end‐group efficiency for the nematic phase using model bicyclo[2.2.2]octanes

The synthesis is reported of new liquid crystals incorporating the 1,4‐disubstituted bicyclo[2.2.2]octane ring and a series of substituents in a terminal position on the molecular core. The nature of the terminal substituent is varied from apolar with a small dipole moment to polar with a strong dipole moment. The angle of the dipole moment with respect to the molecular axis is also varied. An updated order of terminal group efficiency for substituents in a terminal position for the nematic phase is provided. The bicyclo[2.2.2]octane ring shields halogen substituents in a lateral position on phenyl rings attached to the bicyclooctane ring to a small degree and reduces the steric efects of these substituents, giving rise to high relative nematic–isotropic transition temperatures.     

Terminal end-group efficiency for the nematic phase using model bicyclo[2.2.2]octanes

The synthesis is reported of new liquid crystals incorporating the 1,4-disubstituted bicyclo[2.2.2]octane ring and a series of substituents in a terminal position on the molecular core. The nature of the terminal substituent is varied from apolar with a small dipole moment to polar with a strong dipole moment. The angle of the dipole moment with respect to the molecular axis is also varied. An updated order of terminal group efficiency for substituents in a terminal position for the nematic phase is provided. The bicyclo[2.2.2]octane ring shields halogen substituents in a lateral position on phenyl rings attached to the bicyclooctane ring to a small degree and reduces the steric efects of these substituents, giving rise to high relative nematic-isotropic transition temperatures.     

Equilibrium polymerization behavior in the cationic single ring‐opening polymerization of bicyclo orthoesters

The synthesis and cationic polymerization of the following bicyclo orthoesters were examined: 4‐ethyl‐2,6,7‐trioxabicyclo[2.2.2]octane, 1,4‐diethyl‐2,6,7‐trioxabicyclo[2.2.2]octane, 4‐ethyl‐1‐phenyl‐2,6,7‐trioxabicyclo[2.2.2]octane, 4‐ethyl‐1‐(4‐methoxyphenyl)‐2,6,7‐trioxabicyclo[2.2.2]octane, and 4‐ethyl‐1‐(4‐nitrophenyl)‐2,6,7‐ trioxabicyclo[2.2.2]octane. All the monomers underwent equilibrium polymerization, which was confirmed by the relationships between the polymerization temperature and monomer conversion. The obtained polymers afforded the original monomers via an acid‐catalyst treatment with a low reagent concentration in CH₂Cl₂ at 20 °C. The equilibrium monomer concentration was constant, regardless of the initial reagent concentration, in both polymerization and depolymerization. The bicyclo orthoesters with a bulky and electron‐withdrawing substituent showed a larger equilibrium monomer concentration. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3159–3167, 2001     

Convenient One‐Pot Preparation of Dimethyl Bicyclo[2.2.2]octane‐1,4‐dicarbolylate,a Key Intermediate for a Novel Adenosine A1 Receptor Antagonist

Dimethyl bicyclo[2.2.2]octane‐1,4‐dicarboxylate (4), a key starting material for a novel adenosine A₁ receptor antagonist, was prepared in a one‐pot reaction with convenient workup and improved yield.     

Michael reaction on example of unsaturated ketones of bicyclo[3.3.1]nonane series

Conclusions The reaction of bicyclo[3.3.1]-3,7-nonadiene-2,6-dione with nitromethane under the conditions of the Michael reaction in ether solution proceeds with the formation of 2,6-bis(nitromethyl)bicyclo[3.3.1]-nonane-4,8-dione, while in methanol this reaction leads to the formation of a derivative with the bicyclo[2.2.2]octane structure, specifically 3-carbomethoxymethyl-2-nitrobicyclo[2.2.2]-5-octanone.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2624–2626, November, 1981.The authors thank Yu. T. Struchkova, A. I. Akhmedova, and A. I. Yanovskii for running the x-ray structure analysis.     

Excited state dipole moments and polarizabilities of centrosymmetric and dimeric molecules. I. Model study of a bichromophoric molecule

Refractometric, dielectric and electro-optical absorption measurements are reported for 1-dimethylamino-2,6-dicyano-4-methyl-benzene (I) and 1,4-bis(4′-dimethylamino-3′,5′-dicyanophenyl)bicyclo[2.2.2]octane (II). The evaluation leads to dipole moments and polarizabilities of the ground state as well as the first dipole allowed singlet state. The experimental res excellently substantiate the method of electro-optical absorption measurements in solution. It is shown that the excited dimer wavefunctions of the bichromophoric molecule II localize by solvent induced local site perturbations.     

Polar effects and structural variation in 4-substituted 1-phenylbicyclo[2.2.2]octane derivatives: a quantum chemical study

The transmission of polar effects through the bicyclo[2.2.2]octane framework has been investigated by ascertaining how the geometry of a phenyl group at a bridgehead position is affected by a variable substituent at the opposite bridgehead position. We have determined the molecular structure of several Ph-C(CH(2)-CH(2))(3)C-X molecules (where X is a charged or dipolar substituent) from HF/6-31G and B3LYP/6-311++G molecular orbital calculations and have progressively replaced each of the three -CH(2)-CH(2)- bridges by a pair of hydrogen atoms. Thus the bicyclo[2.2.2]octane derivatives were changed first into cyclohexane derivatives in the boat conformation, then into n-butane derivatives in the anti-syn-anti conformation, and eventually into assemblies of two molecules, Ph-CH(3) and CH(3)-X, appropriately oriented and kept at a fixed distance. For each variable substituent the deformation of the benzene ring relative to X = H remains substantially the same even when the substituent and the phenyl group are no longer connected by covalent bonds. This provides unequivocal evidence that long-range polar effects in bicyclo[2.2.2]octane derivatives are actually field effects, being transmitted through space rather than through bonds. Varying the substituent X in a series of Ph-C(CH(2)-CH(2))(3)C-X molecules gives rise to geometrical variation (relative to X = H) not only in the benzene ring but also in the bicyclo[2.2.2]octane cage. The two deformations are poorly correlated. The rather small deformation of the benzene ring correlates well with traditional measures of long-range polar effects in bicyclo[2.2.2]octane derivatives, such as sigma(F) or sigma(I) values. The much larger deformation of the bicyclo[2.2.2]octane cage is controlled primarily by the electronegativity of X, similar to deformation of the benzene ring in Ph-X molecules. Thus the field and electronegativity effects of the substituent are well separated and can be studied simultaneously, as they act on different parts of the molecular skeleton.     

Synthesis of N‐alkyl‐N′‐aryl or Alkenylpiperazines: A Copper‐Catalyzed C–N Cross‐Coupling in the Presence of Aryl and Alkenyl Triflates and DABCO

Unsymmetrical piperazines are key constituents of many pharmaceuticals. Given that the selective introduction of an aryl and alkyl motif onto the piperazine is not always straightforward, direct arylation and alkenylation of 1,4‐diaza‐bicyclo[2.2.2]octane would obviate the inefficiencies associated with the preparation of these target molecules. We have utilized alkyl halides, aryl or alkenyl triflates, and 1,4‐diaza‐bicyclo[2.2.2]octane for the synthesis of N‐alkyl‐N ′‐aryl or alkenylpiperazines. The optimum conditions are developed using CuCl, t‐BuOL i in NMP . Alkenyl triflates requires N ,N ′‐dimethylethylenediamine and higher temperature to afford the desired cross‐coupled product. Substrates bearing electron‐deficient and electron‐rich groups were successfully coupled under the optimum reaction conditions.     

Derivate des 5, 9-Methano-6, 7,8, 9-tetrahydro-5 H-benzocycloheptens und Umlagerungen zum 1, 4-Äthano-1,2,3,4-tetrahydronaphtalin-System

Derivatives of 5,9-Methano,7,8,9-tetrahydro-5H-benzocycloheptene and Rearrangements to the 1,4-Ethano-I,2,3,4-tetrahydronaphthalene System Reduction of the oxime 2 with Raney alloy gives the amine 3a , with AlH₃ a mixture of the isomeric amines 3a and 3b , whilst LiAlH₄ yields the aziridines 4a and 4b . The bicyclo[3.2.1]octane 4b rearranges under acidic conditions to the bicyclo[2.2.2]octane 5 . The olefin 7 can be converted to the aminoalcohol 9 via the epoxide 8 and to the amine 13 using iodine isocyanate: the carbon skeleto. remains intact. However, treatment of the olefin 17 with iodine isocyanate leads to the bicyclo[2.2.2]octanes 21 and 24 in which a skeletal rearrangement has taken place. The configuration was determined by NMR. and X-ray analysis.     

The stepwise heats of hydrogenation of barrelene,an ab initio study

Ab initio Hartree-Fock calculations at the 6–31G*//3–21G level of theory are reported for bicyclo[2.2.2]-2,5,7-octatriene (barrelene), 1 , bicyclo[2.2.2]-2,5-octadiene, 2 , bicyclo[2.2.2]-2-octene, 3 , and bicyclo-[2.2.2]octane, 4 . The stepwise heats of hydrogenation of 1 were found to be 38.1, 31.8, and 28.4 kcal/mol, respectively. The unusually large heat of hydrogenation for the first double bond is attributed to the destabilizing electronic effects involving the interaction of the three double bonds of 1 .     

Synthesis of 1,4-diazabicyclo[2.2.2]octane

Double intramolecular cyclization of N,N-bis(2-chloroethyl)-N-N-bis(2-cyanoethyl)ethylenediamine leads to 1,4-bis(2-cyanoethyl)-1,4-diazoniabicyclo[2.2.2]octane dichloride, which undergoes decyanoethylation to 1,4-diazabicyclo[2.2.2]octane when it is heated. The structures of the compounds were confirmed by their IR and PMR spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 548–550, April, 1978.     

Face Selectivity of the Diels-Alder Additions of 2-Substituted 5,6-bis((E)-chloromethylidene)bicyclo[2.2.2]octanes

The preparation of 5,6-bis((E)-chlorommethylidene)bicyclo[2.2.2]oct-2-ene ( 13 ), 2,3-bis((E)-chloromethyl idene)-5exo,6exo- and -5endo,6endo-epoxybicyclo[2.2.2] octane ( 14 and 15 ), 5,6-bis((E)-chloromethylidene)-2exo- and -2endo-bicyclo[2.2.2] octanol ( 16 and 17 ) and 5,6-bis((E)-chloromethylidene)-2-bicyclo[2.2.2]octanone ( 18 ) are described. The face selectivity (endo-face vs. exo-face attack onto the exo-cyclic diene) of their cycloadditions to tetracyanoethylene has been determined in benzene at 20°. It is 78/22, 80/20, 60/40, 68/32, 3/97 and 30/70 for 13 , 14 , 15 , 16 , 17 and 18 , respectively.     

Oxidative Dearomatization: Synthesis of Functionalized Bicyclo[2.2.2]octenones,Sigmatropic Shift in Excited State,and Radical-Induced Cleavage of Cyclopropane Ring

Synthesis of novel bicyclo[2.2.2]octenones endowed with a β,γ-enone system in which γ-carbon is substituted with an electron-withdrawing group from simple aromatics is described. Oxa-di-pi-methane reaction of bicyclo[2.2.2]octenones to functionalized bicyclo[3.3.0]octanes and their transformation to bicyclo[3.2.1]octane framework are also presented.     

A new three‐dimensional CdII supramolecular framework constructed from the 1‐[(1H‐tetrazol‐5‐yl)methyl]‐1,4‐diazoniabicyclo[2.2.2]octane ligand

A new tetrazole–metal supramolecular compound, di‐μ‐chlorido‐bis(trichlorido{1‐[(1H‐tetrazol‐5‐yl‐κN²)methyl]‐1,4‐diazoniabicyclo[2.2.2]octane}cadmium(II)), [Cd₂(C₈H₁₆N₆)₂Cl₈], has been synthesized and structurally characterized by single‐crystal X‐ray diffraction. In the structure, each Cd^II cation is coordinated by five Cl atoms (two bridging and three terminal) and by one N atom from the 1‐[(1H‐tetrazol‐5‐yl)methyl]‐1,4‐diazoniabicyclo[2.2.2]octane ligand, adopting a slightly distorted octahedral coordination geometry. The bridging bicyclo[2.2.2]octane and chloride ligands link the Cd^II cations into one‐dimensional ribbon‐like N—H...Cl hydrogen‐bonded chains along the b axis. An extensive hydrogen‐bonding network formed by N—H...Cl and C—H...Cl hydrogen bonds, and interchain π–π stacking interactions between adjacent tetrazole rings, consolidate the crystal packing, linking the poymeric chains into a three‐dimensional supramolecular network.     

Novel bicyclo[2.2.2]octanyl-1,4-benzodiazepinones. Their syntheses and rearrangement to bicyclooct-2-enylbenzimidazoles

The synthesis of the novel bicyclo[2.2.2]octanyl[1,4]benzodiazepinone ring system (IV) and its facile acid catalysed rearrangement to the corresponding bicyclo[2.2.2]oct-2-enylbenzirnid-azole system (IX) is described.