bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tritylketone und Tritylenone. Beiträge zur sterisch erzwungenen Michael‐Addition und zur diastereoselektiven Aldol‐Addition
Authors: Seebach Dieter , Ertas̨ Mümtaz , Locher Rita , Bernd Schweizer W. 
Published: December 2004

Tritylketones and Tritylenones. Contributions to the Sterically Enforced Michael Addition and to the Diastereoselective Aldol AdditionTritylketones are prepared from trityllithium and aldehydes, with subsequent CrO3 oxidation (Scheme 1, 2a‐f). Tritylenones are obtained from the saturated ketones and aldehydes or ketones, preferably by (CH3)3Al‐mediated aldol addition with subsequent dehydration (Scheme 2, products 2e, 4b‐e). The carbonyl of the tritylketone group is sterically protected, but electronically effective (see A‐C); thus, amine‐free enolate solutions can be obtained directly with BuLi; also, exclusive conjugate addition of organolithium derivatives occurs with tritylenones (Schemes 3‐5, products 2d, 5‐7, 15 examples). The lithiumenolates of tritylketones add to aldehydes with practically complete stereoselectivity (Scheme 6, products 10, 9 examples): due to the bulkiness of the trityl group, only the (Z)‐enolates 8 are formed, and the approach of the two trigonal centers in the aldol‐addition step is enforced to occur with relative topicity ul. As a first example of an X‐ray structure determination of a silyl enol ether, the crystal structure of (Z)‐2‐(trimethylsilyloxy)‐1, 1, 1‐triphenyl‐2‐butene (9) is reported. Fortunately, the blocking of the carbonyl group in trityl ketones can be run very specifically (without epimerization at the α‐carbonyl center) by lithium triethylborohydride to furnish, after aqueous workup, primary alcohols and Ph3CH (Eqn. 4, products 13–20, 10 examples); the OH‐group of the aldols 10 must be EE‐, MOM‐ or MEM‐protected (Scheme 8) before this C,C‐bond cleavage can be conveyed. Some of the cleavage products are used for the chemical correlation of the aldol configuration and for the demonstration of the synthetic value of the presented method (see 21–29).
Synthesis of Macrobicyclic Polyamines by Direct Macrobicyclisation via Tripode‐Tripode Coupling
Authors: Dietrich Bernard , Hosseini Mir Wais , Lehn Jean‐Marie , Sessions Richard B. 
Published: December 2004

AbstractThe synthesis of five macrobicyclic polyamines 1–5 is described following a route in which the macrobicycle is formed by the coupling of two tripodal subunits. Such a sequence is appreciably shorter than the stepwise construction via a macrocycle, and may give higher yields, as illustrated by the case of bis‐tren 3, which has been synthesized following both routes.
On Cardioactive Steroids. XVI. Stereoselective β‐Glycosylation of Digitoxose: The Synthesis of Digitoxin
Authors: Wiesner Karel , Tsai Thomas Y. R. , Jin Haolun 
Published: December 2004

AbstractTwo methods for stereoselective β‐glycosylation of digitoxose were developed. The first achieved stereocontrol by a 1,3‐participation of a N‐methylurethane group under acid catalysis. The second utilized mercuric‐ion catalyzed cleavage of thioglycosides and a 1,3‐participation of a p‐methoxybenzoyl group in a neutral medium. The first highly stereoselective and quite efficient synthesis of digitoxin (C7) was achieved by a combination of these methods. The furyl‐substituted precursor IV of digitoxigenin (Scheme 1) was used as aglycone, and the furan group was converted to the unsaturated lactone of digitoxin by our known oxidation procedure (m‐chloroperbenzoic acid/NaBH4) after the assembly of the carbohydrate portion of the molecule and its deblocking was completed.
Reduktion von 1,2‐bis[(Z)‐(2‐nitrophenyl)‐NNO‐azoxy]benzol: Synthese von Cyclotrisazobenzol ( = (5E,6aZ,11E,12aZ,17E,18aZ)‐5,6,11,12,17,18‐Hexaazatribenzo[aei][1,3,5,7,9,11]cyclododeca‐hexaen)
Authors: Hilpert Hans , Hoesch Lienhard , Dreiding André S. 
Published: December 2004

Reduction of 1,2‐Bis[(Z)‐(2‐nitrophenyl)‐NNO‐azoxy]benzene1: Synthesis of Cyclotrisazobenzene ( = (5E,6aZ,11E,12aZ,17E,18aZ)‐5,6,11,12,17,18‐Hexaazatribenzo[aei][1,3,5,7,9,11]cyclododeca‐hexaene)Na2S reduction of 1,2‐bis[(Z)‐(2‐nitrophenyl)‐NNO‐azoxy]benzene (2) yielded 3 deoxygenated products: the (known) red 2,2′‐((E,E)‐1,2‐phenylenbisazo)dianiline (3, 23%), the orange 2‐[2‐((E)‐2‐aminophenylazo)phenyl]‐2H‐benzotriazol (4, 55%) and the colorless 2,2′‐(1,2‐phenylene)di‐2H‐benzotriazol (5, 13%). The constitutions of 3–5 and of 6, the N‐acetyl derivative of 4, were deduced from their 1H‐NMR spectra (chemical shifts, couplings, and symmetry properties), and the configurations of 3, 4, and 6 at their N,N‐double bonds are assumed to be the same as in 2. Oxidation of 3 with 2 mol‐equiv. of Pb(OAc)4 afforded 5 (47%) and a novel, highly symmetrical macrocycle, called cyclotrisazobenzene (7, 24%). The constitution of 7 as a tribenzo‐hexaaza[12]annulene and its (E)‐configuration at the N,N‐bonds was confirmed by X‐ray analysis. The molecular symmetry expressed by the 1H‐, 13C‐ and 15N‐NMR spectra of 7 reveals a rapid torsional motion around the six N,C bonds. This implies that the N,N‐double bonds in the cyclic 12π‐electron system (or 24π‐electron system if the benzene rings are included) of 7 are highly localized.
Synthesis and Diels‐Alder Reactivity of 1‐(Dimethoxy)methyl‐2,3,5,6‐tetramethylidene‐7‐oxabicyclo[2.2.1]heptane. Preliminary communication
Authors: Métral Jean‐Luc , Vogel Pierre 
Published: December 2004

AbstractA short synthesis of the title compound 13 is reported. The acetal group in 13 enables one to control the regio‐ and stereoselectivity of the two successive Diels‐Alder additions of the tetraene. The first addition is significantly faster than the second one, thus making 13 a versatile reagent for regio‐ and stereoselective ‘tandem’ cycloadditions.
The Radical Anions of [2.2]Paracyclophane‐1,9‐diene and Some of its Derivatives. An Unexpected Conformational Interconversion
Authors: Bruhin Jürg , Gerson Fabian , Möckel Reinhart , Plattner Georges 
Published: December 2004

AbstractThe radical anions of [2.2]paracyclophane‐1,9‐diene (2) and its 1,10,12,13,15,16‐hexadeuterio derivative 2‐D6, as well as those of 4,5,7,8‐tetramethyl[2.2]paracyclophane‐1,9‐diene (3) and its 12,13,15,16‐tetradeuterio derivative 3‐D4, have been studied by ESR spectroscopy. The coupling constants for 2−· at 178 K are 0.422 mT for four equivalent olefinic protons and 0.046 and 0.020 mT, each for a set of four equivalent aromatic protons. This hyperfine pattern is consistent with either benzene ring bearing two pairs of equivalent protons and it points to a lowering of the anticipated D2h symmetry. The ESR spectra of 2−· are strongly temperature dependent, due to modulation of the two coupling constants of 0.046 and 0.020 mT; these have opposite signs and average to 0.013 mT at 273 K. The experimental findings are interpreted in terms of a transition state of D2h symmetry, 33 kJ/mol above two interconverting equivalent conformations of lower symmetry. Several pieces of evidence suggest that this symmetry is D2, i.e., the benzene rings in 2−· are twisted in opposite directions about the vertical axis. Temperature dependence of the ESR spectra, resulting from modulation of the hyperfine interactions with the aromatic protons, is also observed for 2‐D6−· and 3−·. In the case of 3−·, the olefinic protons are, as expected, only equivalent in pairs, the pertinent coupling constants being 0.560 and 0.325 mT. Upon standing at low temperatures, 2−· and 3−· gradually convert into the radical anions of [2.2]paracyclophane (1) and its 4,5,7,8‐tetramethyl derivative, respectively. At higher temperatures, cleavage of one bridging chain in 2−· also occurs, with the formation of the radical anion of (E)‐4,4′‐dimethylstilbene (7). Both reactions of 2−· must involve the transient radical anion of [2.2]paracyclophane‐1‐ene (4) as proved by the observation of the spectra of 1−· and 7−· with 4 as the starting material.
Acid‐Catalysed Rearrangements of α‐Vinylcyclobutanones
Authors: Jackson David A. , Rey Max , Dreiding André S. 
Published: December 2004

AbstractThe BF3 · Et2O‐ and the CH3SO3H‐catalysed rearrangements of 10 α‐vinylcyclobutanones have been examined. With little acid, the β,β‐dialkyl derivatives 1 were transformed into linear dienones 2 and 3; with more acid, they were converted into cyclopentenones 4 by Nazarov cyclisation of initially formed 2/3. The β‐monoalkyl (including the β,γ‐dialkyl) derivatives 7 rearranged only with a high acid concentration to afford the cyclopentenones 8 by 1,2‐acyl migration. In the case of 7a, the cyclopentenone 8a was accompanied by the unexpected constitutional isomer 9a, which is explained by a reversible interconversion of the cyclobutanone 7a with its isomer 19 via a cyclopropane intermediate like 18. In the case of the β,β‐dialkyl derivative 5, which contains an α‐isobutenyl (instead of an α‐vinyl) group, the acid‐catalysed rearrangement product was the bicyclo[3. 1. 0]hexanone derivative 6.
Rh‐Catalyzed Oxidation of Anthracenes with tert‐Butyl Hydroperoxide. Kinetic Aspects
Authors: Müller Paul , Bobillier Christiane 
Published: December 2004

AbstractThe polar effects of substituents on reactivity in oxidation of 2‐substituted anthracenes with tert‐butyl hydroperoxide (TBHP)/Rh(PPh3)3Cl have been investigated and compared with those obtained with TBHP/VO(acac)2 and chromic acid. The anthracene reactivities obtained from competition experiments are correlated with Hammett's σp‐constants. The P‐values are ‐2.60 for chromic acid and 0.72 for TBHP/VO(acac)2. A poor correlation with p = −0.17 (r = 0.756) was obtained for TBHP/Rh (PPh3)3Cl. It is concluded that the Rh‐catalyzed reaction does not consist in electrophilic oxygen transfer to the anthracene.
Photochemische und chemische Synthesen biologisch aktiver 3‐Oxazoline
Authors: Pfoertner Karl‐Heinz , Montavon François , Bernauer Karl 
Published: December 2004

Photochemical and Chemical Syntheses of Biologically Active 3‐OxazolinesUsing the photoreaction of 2H‐azirines with carbonyl compounds, the 2,2‐dimethyl‐3‐oxazolines 5a, 5b, and 6a have been obtained which bear a mono‐ or dichlorophenyl substituent at C(4) of the five‐membered heterocycle and pyridyl at C(5). These compounds exhibit interesting activities against phytopathogenic fungi. Because 6a had been selected for field testing, its photochemical preparation was supplemented by a chemical synthesis. However, the overall performance of 6a in the field was inferior to some of the recently introduced agricultural fungicides of the ergosterol biosynthesis inhibitor type. Although 16 additional 3‐oxazolines with varied substituents have been prepared, the fungicidal activity found with 6a could not be improved.
Photochemical reactions. 143rd communication. Photochemistry of 5,6‐epoxy‐1,3‐dienes in the ionone series. Influence of a hydroxy group in the 7‐position
Authors: Goldener Urs , Scheller Markus E. , Mathies Peter , Frei Bruno , Jeger Oskar 
Published: December 2004

AbstractThe synthesis and photolyses of the epoxydiene (E)‐5 are described. On triplet excitation (λ > 280 nm, acetone), (E)‐5 undergoes initial cleavage of the C(5)O bond leading to the intermediate c. Presumably an H‐shift (c → e) followed by the fragmentation of the 1,4‐diradical e leads (via the enol 37) to the diketones (E)‐6 and (Z)‐12. Alternatively cleavage of the C(6)C(7) bond of c furnishes the diradical intermediate d which reacts by recombination leading to (E)‐13A + B, 16, and 17A + B, or by an H‐shift to the enol intermediate 38. The latter undergoes an aldol‐type reaction to (E/Z)‐14A + B and (E/Z)‐15A + B, as well as a photochemical [2 + 2]‐cycloaddition to 18. On singlet excitation (λ = 254 nm, MeCN), (E)‐5 undergoes photocleavage to the carbene intermediates f and g. The vinyl carbene f reacts with the adjacent double bond furnishing the cyclopropene 22 as the main product. From the carbene intermediate g, compounds 23, 24, and 25 arise by carbene insertion into the neighboring CC or CH bond. Furthermore, the diastereomer of the starting material, the epoxydiene (E)‐20, is formed via the ylide intermediate h.
Conformational Studies on Potential β‐Turn‐Forming Model Peptides
Authors: Bode Karsten , Goodman Murray , Mutter Manfred 
Published: December 2004

AbstractThe conformational behavior of POE‐bound model peptides Boc‐(L‐Ala)2‐X‐Y‐(L‐Ala)2‐NHPOE (X – Y = L‐Pro‐Gly (I), Gly‐L‐Ile (II); NHPOE = aminopoly(oxyethylene)) as well as of the repetitive hexapeptide of elastin, Boc‐L‐Val‐L‐Ala‐L‐Pro‐Gly‐L‐Val‐Gly‐A‐NHPOE‐M (III) (A = photosensitive 3‐nitro‐4‐(bromomethyl)benzoyl group; NHPOE‐M = aminopoly(oxyethylane) monomethyl ether) has been studied by means of 1H‐NMR and CD spectroscopy. Compounds I and III form a β‐turn with Pro and Gly in positions i + 1 and i + 2, respectively, while an aggregated state for II, has been identified. The results are in good agreement with published prediction codes giving experimental evidence for the dominance of short‐range interactions to establish secondary structure in solution.
The adamantane rearrangement of 1,2‐trimethylenenorbornanes. Part V. Rearrangements of 1,2‐trimethylenenorbornanes initiated by regioselective formation of carbocation centers at C(2) and C(6)
Authors: Klester Alfred Michael , Ganter Camille 
Published: December 2004

AbstractThe behaviour of the regioselectively generated carbocation centers at C(2) and C(6) in 1,2‐trimethylenenorbornanes was investigated in order to study the occurrence or absence of a degenerate rearrangement E⇄M in the adamantane rearrangement of both 1,2‐endo‐ (1) and 1,2‐exo‐trimethylenenorbornane (2) to 2‐endo,6‐endo‐trimethylenenorbornane (3). A degenerate rearrangement E⇄M is inevitably involved inasmuch as a 1,2‐trimethylenenorborn‐2‐yl cation E not only is formed directly as manifested by the conversions of the reactants 4 (C(2), C(3)‐olefin) and 6 (C(2), C(3′)‐olefin), but also indirectly (via F→E) if the leaving group at C(6) to be ionized occupies the endo‐position (6‐endo‐alcohol 8). No degenerate rearrangement E⇄M is operative starting from reactants that lead directly to a 2,6‐trimethylenenorborn‐2‐yl cation G; this is the case with both the ionization of the 6‐exo‐alcohol 10 having the leaving OH‐group in a stereoelectronically favoured configuration to undergo simultaneous C(1), C(2)‐bond migration (→G) as well as the protonation of the olefin 13 which is followed by same reaction pathway.
Synthesen von Dibenzo[b,e][1,4]dioxin‐2,3‐chinonen, einschliesslich der Ecklonochinone A und B sowie der Isoecklonochinone A und B
Authors: Lütolf Walter Leo , Prewo Roland , Bieri Jost H. , Rüedi Peter , Eugster Conrad Hans 
Published: December 2004

Syntheses of Dibenzo[b,e][1,4]dioxin‐2,3‐quinones Including the Ecklonoquinones A and B and the Isoecklonoquinones A and BOxidation of monomesyloxy‐substituted pyrocatechols with MnO2 in toluene using phase‐transfer conditions leads in high yield to monomesyloxy‐substituted dibenzo[b,e][1,4]dioxin‐2,3‐quinones with loss of one mesyloxy group. In this way, ecklonoquinone A (2), ecklonoquinone B (3), isoecklonoquinone A (43), and isoecklonoquinone B (44) were prepared. Their structures are based on X‐ray analyses of ecklonoquinone‐A leucoacetate (45) and the mesyloxy‐substituted quinone 20. The reddish‐violet dibenzodioxin‐diquinone 49 was prepared from an intermediate of the iso‐series. The parent compound 1 has been synthesized in yields better than 50% from pyrocatechol and methyl 2,5‐dioxo‐2,5‐dihydrobenzoate as oxidant and 2‐methoxypyridin as catalyst. To rationalize the specific effect on the dimerisation step of the mesyloxy group, the intermediacy of 1,4‐quinone monoacetals is proposed. This also applies to a proposed biogenetic scheme.
Bis (2,4,6,8‐cyclononatetraen‐1‐yl)methane
Authors: Sabbioni Gabriele , Neuenschwander Markus 
Published: December 2004

Bis (2,4,6,8‐cyclononatetraen‐1‐yl)methanesBis (2,4,6,8‐cyclononatetraen‐1‐yl)methanes (2a–c) have been prepared by reaction of all‐cis‐cyclononatetraenide with 1,1‐dichlorodimethyl ether as well as with carbenium ion precursors 9b and 9c. The title compounds 2 are attractive precursors of highly delocalised nonafulvenes of type 3; however, elimination experiments 2→3 failed so far.
Transferts d'hydrogènes dans les cations radicaux ethylène‐acetals dérivés de cyclopentanones et cyclohexanones
Authors: Audier H. E. , Tabet J. C. , Fetizon M. 
Published: December 2004

Hydrogen Transfer during Decompositions of Molecular Ions of Acetals Derived from Substituted Cyclopentanones and CyclohexanonesThe isomerisation process of ethylene‐acetal radical ions of low internal energy has been reinvestigated in more detail. The ring contraction of cyclohexane derivatives into methylcyclopentanes is quite general for these ions. The relative rates of [1, n] H transfers to the C free radical resulting from CC cleavage α to the acetal group plays the most important part in the mechanism.
Photochemical reactions. 144th Communication. Photochemistry of 5,6‐epoxy‐1,3‐dienes in the ionone series: Influence of a methoxy group in position 7
Authors: Goldener Urs , Frei Bruno , Jeger Oskar 
Published: December 2004

AbstractOn triplet excitation (λ > 280 nm, acetone), the epoxydiene (E)‐5 undergoes initial cleavage of the C(5)O bond of the oxirane and subsequent cleavage of the C(6)C(7) bond leading to the diradical intermediate e which reacts by recombination furnishing the cyclic compounds (E/Z)‐6, (E/Z)‐7,8, and 9. Alternatively, a H‐shift leads to the aliphatic methyl‐enol ether 10 which undergoes a photochemical [2+2]‐cycloaddition to compounds 12 and 13, the main products on triplet excitation of (E)‐5. On singlet excitation (λ = 254 nm, MeCN), (E)‐5 undergoes cleavage to the carbene intermediates f and g. The vinyl carbene f reacts with the adjacent double bond furnishing the cyclopropene 14 as the main product. From the carbene intermediate g, the methyl‐enol ether 15 arises by carbene insertion into the neighboring CH bond. Furthermore, the diastereomer of the starting material, the epoxydiene (E)‐16, and compounds 17A+B are formed via the ylide intermediate h. Finally, the cyclobutene 18 is the product of an electrocyclic reaction of the diene side chain.
Synthèse de l'ériodermine
Authors: Pulgarin César , Gunzinger Jan , Tabacchi Raffaele 
Published: December 2004

Synthesis of ErioderminThe total synthesis of eriodermin (=2,7‐dichloro‐4‐formyl 3‐hydroxy‐8‐methoxy‐1,6‐dimethyl‐11H‐dibenzo[b,e] [1,4]dioxepin‐11‐one) is described.
Photochemical reactions. 145th Communication. Carbonyl vs. epoxyketone photochemistry: Photolysis of 1,2;3,4‐diepoxy‐2,6,6‐trimethyl‐1‐cyclohexyl methyl ketone
Authors: Phaff Rox , Bischofberger Norbert , Mathies Peter , Petter Walter , Frei Bruno , Jeger Oskar 
Published: December 2004

AbstractThe synthesis and photolysis of the title compound 3 is described. Irradiation (λ > 280 nm, MeCN) of the di‐epoxyketone 3 leads predominantly to γ–H abstraction. Cyclization furnishes the cyclobutanols 22–24, while cleavage gives compound 25, presumably via the allene‐oxide intermediate 36. Further, products 27 and 28 are formed by Norrish fragmentation and by initial cleavage of the C(α)O bond of the oxirane, respectively. The structures of the products 22–25, 27, and 28 were assigned on the basis of the spectral data of the photolysis products of the 13C‐labelled diepoxyketone[6,6‐dimethyl‐13C2]‐3 and by X‐ray analysis of the compounds 24 and 35, the latter being the p‐nitrobenzoate of 22.
Unusual Acid‐Catalyzed Rearrangement of Two α,α′‐Diimino‐oximes
Authors: Fuhrer Walter , Rasetti Vittorio , Rihs Grety 
Published: December 2004

Abstract2‐[2‐(Alkylimino)‐2‐phenylethylidene]pyrrolidines (vinamidines, 3–6) were obtained either via activation of the corresponding vinologous amide 1 with Meerwein salt and subsequent treatment of the intermediate 2 with an amine, or more directly by acid‐catalyzed condensation of the Schiff bases derived from acetophenone with 2‐ethoxy‐1‐pyrroline. Nitrosation of these vinamidines led to α,α′‐diimino‐oximes. In two cases (10, 11), these oximes underwent acid‐catalyzed rearrangement with formation of a 5,6,7,8‐tetrahydroimidazo[1,2‐a]pyridine ring system (12, 13). X‐Ray analysis of one of these products (13) and also of one of the vinamidine salts (6) are presented.
Oberflächenmodifikation von Kohlenstoff‐Elektroden durch Zweikomponenten‐Polymere, aufgebaut aus Epoxidharzen und einem Derivat von Vitamin B12
Authors: Ruhe Annette , Walder Lorenz , Scheffold Rolf 
Published: December 2004

Surface Modification of Carbon Electrodes by Polymers Consisting of Epoxy Resins and a Derivative of Vitamin B12A derivative of vitamin B12 containing a 3,5‐diaminobenzoyl group in the c side‐chain has been synthesized. It was used as the amine component in the formation of an optically active cross‐linked epoxy‐polymer. Surface modification of carbon electrodes (basal plane graphite and carbon felt) has been achieved by impregnating them with solutions of the monomers followed by thermal curing at 120°C. Electrochemical responses of the Co(II)/Co(I) redox system from sub‐mono to multilayer coverages have been observed. The polymer exhibits catalytic activities typical for monomeric vitamin B12 as shown by spectroscopic and electrochemical techniques. Polymermodified electrodes with large specific surfaces have been used in organic electrosynthesis, i.e. the exclusive formation of valeronitrile by reductive cross‐coupling of ethyl iodide and acrylonitrile.
Metal Complexes with Macrocyclic Ligands. Part XXI. A nonlinear relationship between the stability of Cu2+ complexes and their complexation rate with 1,4,8,11‐tetraazacyclotetradecane
Authors: Wu Yi‐he , Kaden Thomas A. 
Published: December 2004

AbstractThe kinetics of the reaction (1) between 1,4,8,11‐tetraazacyclotetradecane (Cy) and a series of Cu(II) complexes CuL (L) = glycolate, malonate, succinate, picolinate, glycinate, iminodiacetate, nitrilotriacetate, N‐(2‐hydroxyethyl)ethylenediaminetriacetate, ethyienediamine, 1,3‐diaminopropane, diethylenetriamine and N,N‐bis(3‐aminopropylamine) were studied spectrophotometrically at 25° and I = 0.5 (KNO3). From the analysis of the log kobs/log [L] profiles obtained at different pH values the resolved bimolecular rate constants k (Table 3) were obtained by a nonlinear curve‐fitting procedure. For nearly all systems studied, the rate constant k, describing the reaction between the 1:1 complex CuL and the monoprotonated form of the macrocycle CyH, was obtained. The nonlinear relationship between log k and log KCuL and its nature is discussed. It is shown that the inverse relationship between reactivity and stability described by others is only a special case of the more general Eqn. 3 described here.
The Synthesis of 4,7‐Bis(dialkylamino)tricyclo[5.2.1.04,10]deca‐1(10),2,5,8‐tetraenes and their Reduction with Alkali Metal
Authors: Butenschön Holger , de Meijere Armin 
Published: December 2004

AbstractThe synthesis and characterization of the novel 4,7‐bis(dialkylamino)tricyclo[5.2.1.04,10]deca‐1(10), 2,5,8‐tetraenes 12 from 1,4,7‐trihalotriquinacenes 8 and secondary amines is reported. The structural and electronic characteristics of these as well as the acepentalene dianion (32−) and some related systems as determined by semiempirical (MNDO) calculations are discussed. Thereby, 32− should be a triply etheno‐bridged trimethylenemethane dianion exhibiting Y‐delocalization favored over the formation of a peripheral 10π‐electronic system. Attempts directed towards the generation of 32− by reacting tetraenes 12 with Na led to the formation of tris(dialkylamino)triquinacenes 9, presumably by a kind of reduction/disproportionation mechanism.
Etudes sur les composés organométalliques. Partie XXI. Contribution à l'étude de la décomposition du tétracyclohexyltitane
Authors: Meyer Edouard Marc , Jacot‐Guillarmod André 
Published: December 2004

Studies on Organometallic Compounds. Contribution to the Study of Thermal Decomposition of TetracyclohexyltitaniumThermal decomposition of tetracyclohexyltitanium proceeds in a different manner for the solid compound and for etheral solution. We propose an explanation of the decomposition mechanisms based on radical reactivities and compare our results with previous literature data.