- An experimental thermochemical and theoretical study of triquinacene: Definitive disproof of its neutral homoaromaticity
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The enthalpy of formation (ΔH(f)/°(g) = 57.51 ± 0.70 kcal/mol) of triquinacene (1), newly determined by measuring its energy of combustion in a microcalorimeter, is about 4 kcal/mol higher than that previously reported and corresponds to ab initio and density functional theory computational results. As a consequence, the previously derived homoaromatic stabilization energy (claimed to be 4.5 kcal/mol) from enthalpy of hydrogenation measurements is not present in 1. The lack of homoaromaticity in 1 is supported by evaluation of geometric, energetic, and magnetic criteria. In contrast, the isomerization transition state from diademane (5) to 1 is highly aromatic on the basis of the same criteria. The enthalpy of isomerization of 5 to 1 was experimentally determined by differential scanning calorimetry (DSC) to be -29.4 ± 0.3 kcal/mol (measured at 368.2 K). The enthalpy of activation for this rearrangement as determined from the DSC measurements (28.4 ± 0.2 kcal/mol) is 2.5 kcal/mol higher than the value computed at B3LYP/6311+G**+ZPE.
- Verevkin, Sergey P.,Beckhaus, Hans-Dieter,Rüchardt, Christoph,Haag, Rainer,Kozhushkov, Sergei I.,Zywietz, Tosja,De Meijere, Armin,Jiao, Haijun,Von Ragué Schleyer, Paul
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- THE SYNTHESIS OF TRIQUINACENE VIA THE WEISS REACTION.
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A short, simple preparation of triquinacene 1 is based on four key steps: the Weiss reaction, high-yield monoalkylation of the resulting bicyclo system, aldol cyclization of aldehyde 6 and HMPA-mediated dehydration of triol 8.
- Bertz, Steven H.,Lannoye, G.,Cook, J. M.
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- Thermochemical and x-ray crystallographic investigations of some (CH)10 hydrocarbons: Basketene, Nenitzescu's hydrocarbon, and snoutene
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The enthalpies of formation [ΔHf0 (g)] of pentacyclo[4.4.0.02,5-.03,8.04,7]dec-9-ene (9, basketene) and pentacyclo[4.4.0.02,4.0-3,8.05,7]dec-9-ene (14, snoutene) have been determined by measurement of their heats of combustion in a microcalorimeter as 110.2 ± 0.5 kcal·mol-1 and 78.4 ± 0.3 kcal·mol-1, respectively. These values and the strain energies (SEs) [SE(9) = 110.3 kcal·mol-1, SE(14) = 78.4 kcal·mol-1] derived from them were compared with values obtained from MM2/MM3 calculations. The enthalpy of isomerization of 9 to tricyclo[4.2.2.02,5]deca-3,7,9-triene (8, Nenitzescu's hydrocarbon) was measured by differential scanning calorimetry (DSC) as -20.7 ± 0.3 kcal·mol-1 (384.1 K), corresponding to a strain energy SE(8) of 44.6 kcal·mol-1. The enthalpy of activation for this rearrangement was also determined from the DSC measurements to be 28.6 ± 0.1 kcal·mol-1. The obtained strain energies and the derived heats of isomerization to 9,10-dihydronaphthalene (7) did not correlate in any way either with the activation energies of the thermal isomerizations of these (CH)10 hydrocarbons or with the structural features determined experimentally for basketene (9) and computationally (DFT at the B3LYP/6-311+G* level) for snoutene (14). Compounds 8, 9, 10, and 14 exhibited solid-state phase transitions in a narrow temperature range (-55 to -70 °C), whereas the melting points or rearrangement temperatures varied to a much greater extent (in the 0-126°C range). Compound 9 formed intermediate plastic phases, 8 had a plastic and a disordered phase, while 10 and 14 both formed phases intermediate between plastic and disordered. Crystal structure determinations based on disordered models could be carried out for 10 and 14. Basketene 9 could be crystallized from solution directly into the ordered phase at low temperatures (-178 °C). The obtained molecular geometry contrasted with results from an older gas-phase diffraction study, but agreed very well with DFT calculations. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Verevkin, Sergei P.,Kuemmerlin, Martin,Hickl, Ernst,Beckhaus, Hans-Dieter,Ruechardt, Christoph,Kozhushkov, Sergei I.,Haag, Rainer,Boese, Roland,Benet-Bucholz, Jordi,Nordhoff, Karsten,De Meijere, Armin
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p. 2280 - 2287
(2007/10/03)
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- LiCB11Me12: A catalyst for pericyclic rearrangements
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(matrix presented) Benzene and 1,2-dichloroethane solutions of the Li+ salt of the weakly coordinating anion CB11Me12- catalyze the rearrangement of cubane to cuneane, quadricyclane to norbornadiene, basketene to Nenitzescu's hydrocarbon, and diademane to triquinacene. The Claisen rearrangement of phenyl allyl ether is also strongly accelerated.
- Moss, Stefan,King, Benjamin T.,De Meijere, Armin,Kozhushkov, Sergei I.,Eaton, Philip E.,Michl, Josef
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p. 2375 - 2377
(2007/10/03)
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- General Approach to the Synthesis of Poliquinenes. 8. Synthesis of Triquinacene, 1,10-Dimethyltriquinacene, and 1,10-Cyclohexanotriquinacene
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The synthesis of tricyclo4,10>deca-2,5,8-triene (1), 1,10-dimethyltricyclo4,10>deca-2,5,8-triene (3), and tetracyclo1,8.04,8>tetradeca-2,5,13-triene (4) has been accomplished via the reaction of 1,2-dicarbonyl compounds with di-tert-butyl 3-oxoglutarate (Weiss reaction).Condensation of glyoxal 5a with di-tert-butyl 3-oxoglutarate (6b) gave the tetra-tert-butyl cis-dioxobicyclooctane-2,4,6,8-tetracarboxylate 7b in 93percent yield.This bisenol 7b was converted into the bisenol ether 9b regiospecifically (90percent yield).This transformation was followed by monoalkylation (KH, allyl iodide; -58 deg C) and hydrolysis to generate 2-allyl-cis-bicyclooctane-3,7-dione in 90percent overall yield from 9b.The mixture of epimiric 2-allyl-3,7-diones 11a,b was transformed (O3; DMS) into the mixture of epimiric aldehydes 12a,b.This process was followed by aldol cyclization (2 N HCl, THF) to provide the diastereomeric mixture of of endo-(13a) and exo-(13b) triquinane monols in 85percent yield.Reduction of 13a,b with borane-THF (0 deg C) generated the stereoisomeric mixture of triols 14a,b which were subjected to an HPMA-mediated dehydration sequence to provide triquinacene (1), accompanied by small amounts of isotriquinacene.The mixture of trienes were converted into pure 1 by exposure to p-TSA in methylene chloride-pentane.Substitution of biacetyl (5b) for glyoxal 5a in the Weiss reaction, followed by the analogous steps detailed in the synthesis of 1, provided 1,10-dimethyltriquinacene (3).In addition, the synthesis of 1,10-cyclohexanotriquinacene (4), another centro-substituted triquinacene, has been accomplished by substitution of cyclohexane-1,2-dione (23) for 5a in the condensation, followed by the same sequence of reactions presented above for 1 and 3.
- Gupta, Ashok K.,Lannoye, Greg S.,Kubiak, Greg,Schkeryantz, Jeff,Wehrli, Suzanne,Cook, James M.
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p. 2169 - 2179
(2007/10/02)
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- Bridgehead Olefinic Isomers of Triquinacene: Derivatives of Tricyclo4,10>deca-1,5,8- and -1,6,8-triene
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Bridgehead halides 12 and 13 of triquinacene (2) with soft nucleophiles undergo a syn-stereoselective SN2' reaction forming derivatives of tricyclo4,10>deca-1,5,8-triene 15 and 17, respectively, and of tricyclo4,10>deca-1,6,8-triene 18.The relative stability of these bridgehead olefins is discussed with regard to force field calculations as well as semiempirical MNDO calculations.
- Butenschoen, Holger,Meijere, Armin de
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p. 2757 - 2776
(2007/10/02)
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- Diademane and Structurally Related Compounds, I. Preparation and Characteristic Reactions of Some Tris-?-homobenzene Hydrocarbons
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Diademane (5) and 1,6-Homodiademane (6) are the first hydrocarbons with cis-tris-?-homobenzene skeletons.They were prepared by photoisomerization of the olefinic precursors 8 (snoutene) and 15 (4,5-homosnoutene), respectively.In an analogous reaction the bridged trans-tris-?-homobenzene 7 was formed from 17 (endo,exo-bishomobarrelene). 7 is more easily obtained from 17 by rhodium(I)-catalyzed isomerization or from exo,exo-bishomobarrelene 18 by thermal rearrangement.The unbridged 4 was prepared using a newly developed synthetic sequence starting from 1,3-cyclohexadiene.The thermal rearrangement of 5 and 6 to triquinancene (9) and 1,10-homotriquinancene (16) is very facile; the gas phase kinetic parameters (ln k (5) = 33.7 - 31600/RT and ln k (6) = 32.2 - 28300/RT, both first order) strongly corroborate, that these rearrangements are concerted ?2S + ?2S + ?2S> cycloreversions. -labelled 4 upon thermolysis yields a trans-bicyclonona-3,7-diene (31 22) with a 12C-labelling pattern, which proves its formation via a 3-step mechanism.The first step in this sequence most probably is a ?2S + ?2S + ?2S> cycloreversion with ln k = 30.8 - 42000/RT (first order).Only the bridged compound 7 does not follow the sample path, probably due to excessive ring strain in the transition state, and prefers a stepwise cycloreversion leading to 18 and at least 5 secondary products.
- Kaufmann, Dieter,Fick, Hans-Heinrich,Schallner, Otto,Spielmann, Werner,Meyer, Lueder-Ulrich,et al.
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p. 587 - 609
(2007/10/02)
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- Diademane and Structurally Related Compounds, II. Catalytic Rearrangements and Hydrogenations
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Copper, silver, gold, and rhodium compounds catalyze the rearrangement of diademane (1) to triquinacene (5) and snoutene (7), respectively.Known mechanism may be adopted to explain this behaviour.The catalytic hydrogenation of 1 leads to a mixture of 6 products, 9 - 14, the composition of which was independent of the extent of reaction.Adamantane, the thermodynamically most stable isomer of all conceivable "hexahydrodiademanes", was not detected.
- Kaufmann, Dieter,Schallner, Otto,Meyer, Lueder-Ulrich,Fick, Hans-Heinrich,Meijere, Armin de
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p. 1377 - 1385
(2007/10/02)
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