bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular Ions of Transient Species: Vinyl‐Alcohol Cation
Authors: Albrecht Bruno , Allan Michael , Haselbach Edwin , Neuhaus Louis , Carrupt Pierre‐Alain 
Published: December 2004

AbstractVinyl alcohol 1 was prepared by thermolysis of cyclobutanol and its photoelectron spectrum was determined. I = 9.18 eV and I = 9.52 eV were found, the vibrations progression (ṽ = 1400 cm−1) for this lowest energy transition 1(X)→1+(X̃) indicating significant skeletal changes in the ion. The question of the relative stability of the syn (1)‐ vs. anti‐ions (1) is discussed in the light of theoretical calculations. The energy of the second π‐state of 1+ is estimated at 13.6–14.1 eV above the ground state of 1.
Synthese von Bicyclo[3.3.o]oct‐1(5)en‐2‐on aus Cyclohexanon
Authors: Lorenzi‐Riatsch Annalaura , Nakashita Yoshihiko , Hesse Manfred 
Published: December 2004

Synthesis of Bicyclo[3.3.0]oct‐1(5)en‐2‐one from CyclohexanoneTreatment of 2‐nitrocyclohexanone (2) with acrylaldehyde yielded in the presence of tetrabutylammonium fluoride the bicyclic product 5, which was oxidized to the nitro‐diketone 3. The conversion of 3 to the title compound 1 was achieved in the nearly quantitative yield under unusual conditions: K2CO3/H2O and H2SO4. Compound 3, was also converted to 1 (stepwise and one‐pot reaction, respectively) by treatment with 1. NaOCH3, 2. TiCl3, and 3. H2SO4 (Scheme).
Protolytic Opening of Two Diastereoisomeric Cyclopropanols
Authors: Schönholzer Peter , Wan Terence S. , Fischli Albert 
Published: December 2004

AbstractCob(I) alamin (1(I))‐catalyzed reduction of the aldehyde 2 led to the two crystalline cyclopropanols 3 and 4 (see Scheme 2). The protolytic ring‐opening starting from 3 produced the saturated aldehydes 6 and 7;8 was formed in traces only (see Scheme 3). The protolysis starting from 3 led, therefore, mainly to retention of configuration at the spiro C‐atom (7); ring‐opening with inversion was observed in traces only (8). Starting from 4, the protolysis produced 9 and 7; the absence of 8 showed this protolysis to proceed 9 and 7; the absence of 8 showed this protolysis to proceed exclusively with inversion of configuration at the spiro center. Of the p‐bromobenzoate 5 (cf. Scheme 2) the structure has been determined by X‐ray analysis.
Stoffwechselprodukte von Mikroorganismen 226. Mitteilung Versuche zur Strukturaufklärung von Niphimycin, 3. Teil. Identität von Scopafungin mit Niphimycin I und Lage des Malonylrestes in Niphimycin und Copiamycin
Authors: Gassmann Peter , Hagmann Leonhard , Keller‐Schierlein Walter , Samain Daniel 
Published: December 2004

Structural Elucidation of Niphimycin, Part 3. Identity of Scopafungin and Niphimycin I. Position of the Malonyl Residue of Niphimycin and CopiamycinThe identity of scopafungin with niphimycin I was proven by spectroscopic and chromatographic methods and by common degradation products. The position of the malonyl residue in niphimycin I (9) and in copiamycin (14) was deduced by 1H‐NMR spin‐decoupling experiments of a degradation product (10).
Preparation of Bicyclo[3.3.0]octane‐2,8‐dione‐ and Declain‐1,8‐dione‐Derivatives
Authors: Duthaler Rudolf O. , Maienfisch Peter 
Published: December 2004

AbstractAlkylation of bicyclo[3.3.0]octane‐2,8‐dione (1), which is prepared by a modification of the procedure described in the literature, gives the methyl‐ and propynyl‐derivatives6and7(Scheme 1). In addition to the method described previously (Scheme 2), 9‐methyl‐cis‐decalin‐1,8‐dione9is obtainable stereoselectively either by cyclization of keto‐acid16, or by aldol cyclization of keto‐aldehyde26and oxydation of the resulting alcohols24and25(Scheme 4). The β‐keto‐alcohols24and25undergo a base‐catalyzed isomerization; thetrans‐decalin isomers27and28are not detected in this equilibrium mixture (Schemes 4and5)l. Monoreduction ofcis‐dione9gives theendo‐alcohol25, while27is the favored product of the reductin oftrans‐dione10(Scheme 4). Optically pure (+)‐25can be prepared from (9S,10R)‐monoacetal29(Scheme 5).
(5R*, 9S*)‐ and (5R*, 9R*)‐2,2,9‐Trimethyl‐1,6‐dioxaspiro[4.4]non‐3‐ene and their Dihydro Derivatives as New Constituents of Geranium Oil
Authors: Kaiser Roman 
Published: December 2004

Abstract(5 R*,9S*)‐ and (5R*,9R*)‐2,2,9‐Trimethyl‐1,6‐dioxaspiro [4.4]non‐3‐ene (1a and 1b resp.) and their dihydro derivatives 2a and 2b are described as new constituents of geranium oil. The structures and configurations of 1a, 1b, 2a, and 2b, are based on spectra interpretation and syntheses. Also some other monoterpenoid constituents identified in the same boiling range are discussed.
Synthesis of the Alleged Natural Monoterpenoid α‐Santolinenone
Authors: Guella Graizano , Cavazza Marino , Guerriero Antonio , Pietra Francesco 
Published: December 2004

AbstractAuthentic α‐santolinenone ( = (+)‐(4R)‐1(7)‐p‐menthen‐2‐one; (+)‐1) is made available for the the first time in 30% overall yield from (+)‐(4R)‐p‐menthene ((+)‐2) via the diastereoisomeric allylic alcohols (+)‐4a/(+)‐4b, which are oxidized to (+)‐1 with Ag2CO3/Celite. Yields are good, except for the last stage; indeed, only alcohol (+)‐4a, with equatorial OH‐group, undergoes oxidation, and (+)‐1 is partly substracted via a hetero Diels‐Alder dimerization giving a mixture of the diastereoisomeric dihydropyrans (+)‐5a/(+)‐5b. When Cr(VI) reagents ae used, (+)‐4a/(+)‐4b mainly give phellandral (6) and carvotanacetone (7), NnO2 reacts too sluggishly with (+)‐4a/(+)‐4b. A camphor pyrolyzate, previously thought to be 1 must be a different compound, probably 7.
Synthese von (S)‐Plectaniaxanthin
Authors: Dumont Raymond , Pfander Hanspeter 
Published: December 2004

Synthesis of (S)‐PlectaniaxanthinThe optically active C10‐end group (S)‐5, prepared from the C5‐aldehyde (R)‐4 (ex L‐serine (2)), has been used for the synthesis of (S)‐plectaniaxanthin (1). The (R)‐chirality of natural 1 assigned by Rønneberg et al. [6] is confirmed.
New Saponins from Phytolacca dodecandra l'HERIT
Authors: Domon Bruno , Hostettmann Kurt 
Published: December 2004

AbstractThree bidesmosidic saponins (1–3) have been isolated from the methanolic extract of the berries of Phytolacca dodecandra l'HERIT (Phytolaccaceae) by a combination of rotation locular counter‐current chromatography and column chromatography on reversed phase (RP‐8) With MeOH/H2O. The structures have been established by 1H‐NMR, 13C‐NMR, FAB‐MS, and D/CI‐MS, as well as on the basis of acidic and basic hydrolyses. The monodesmosidic saponins 1a–3a obtained after partial hydrolysis with a base exhibit strong molluscicidal activity against the schistosomiasis‐transmitting snail Biomphalaria glabrata. Saponins 1–3, 1a, and 3a are reported for the first time, whereas 2a has been identified previously in the aqueous extract of P. dodecandra berries.
The CAMET and CASET links for the synthesis of protected oligopeptides and oligodeoxynucleotides on solid and soluble supports
Authors: Schwyzer Robert , Felder Eduard , Merli‐Failli Paola 
Published: December 2004

AbstractSimple bifunctional carboxy‐ and phospho‐protecting groups are described which allow the attachment of protected amino acids and nucleotides to soluble or insoluble carriers. After chemical synthesis with conventional procedures, the completed oligopeptides or oligonucleotides can be detached by base‐catalyzed β‐elimination, leaving other protecting groups intact. These protected biopolymer segments can then be purified, characterized, and used for further synthetic work by virtue of their free carboxy or phospho groups. It is also possible to deprotect peptides and nucleotides on the supports: this procedure may be used for the preparation of affinity‐chromatographic materials.
Fragmentation of 6‐Deoxy‐6‐halo‐hexono‐1,5‐ortholactones: A Concerted, Nonstereospecific Process
Authors: Bernet Bruno , Vasella Andrea 
Published: December 2004

AbstractThe synthesis of the D‐arabino‐ and D‐ribo‐ortholactones 13a–f and 15b–f and their treatment with Zn leading to the unsaturated esters 14a–d and 16a–d are described. Possible fragmentation mechanisms are discussed. The results were only compatible wit a concerted, nonsynchronous process, where both the axial lone pair of the ring oxygen atom and the lone pair formed during rupture of the C(5), O‐bond participate in the elimination of the axial and of the equatorial C(1)‐alkoxy groups, respectively.
Synthesis and Photochemistry of 2,2‐Dimethyl‐3(2H)‐thiophenone, a Ketonic Tautomer of 3‐Hydroxythiophene. Preliminary Communication
Authors: Anklam Elke , Ghaffari‐Tabrizi Ramin , Hombrecher Hermann , Lau Sabine , Margaretha Paul 
Published: December 2004

AbstractOn irradiation (λ = 366 nm), the 4‐thia‐2‐cyclopentenone 3a behaves in complete analogy to the oxa‐enone 3c undergoing regio‐ and stereospecific cyclodimerization, regiospecific cycloaddition with 2‐methylpropene and cycloaddition with 2,3‐dimethyl‐2‐butene to afford cyclobutane derivatives. In contrast, the 4‐aza‐2‐cyclopentenone 3b does not undergo the above‐mentioned reactions but only slow photodecomposition.
Elektromotorisches Verhalten von Flüssigmembranelektroden‐Messketten mit enantiomerenselektiven chiralen Ionophoren
Authors: Morf Werner E. , Bussmann Walter , Simon Wilhelm 
Published: December 2004

AbstractElectromotive Behaviour of Liquid‐membrane Electrode Assemblies Based on Enantiomer‐selective Chiral IonophoresA comprehensive theoretical treatment is given for the potentiometric behavior of enantiomer‐selective membrane electrodes based on chiral ionophores and plasticizers. The membrane model allows for free and complexed enantiomeric or racemic ions (e.g. ephedronium and l‐phenylethylammonium ions) as well as for achiral interfering ions. Experiments are derived for the determination of the stoichiometry and the relative stability of enantiomeric ion/enantiomeric ligand complexes, and for the analytical measurement of the enantiomeric excess of ions in solution.
An efficient synthesis of α,β‐unsaturated aldehydes by a four‐carbon unit extension of Grignard reagents
Authors: Cloux Roland , Schlosser Manfred 
Published: December 2004

AbstractCopper‐catalyzed addition of organomagnesium halides to 2‐(2,2‐diethoxyethyl)oxirane (1) affords aldol acetals 2 which upon acid treatment undergo hydrolysis and dehydration to give α,β‐unsaturated aldehydes 7 with high yields.
Chemo‐ and Stereoselective Coordination of 5,6‐Dimethylidene‐7‐oxabicyclo[2.2.1]hept‐2‐ene by d8‐ and d6‐Metal Carbonyls. Diels‐Alder reactivity of Dienes Perturbed by Remote Olefin Complexation
Authors: Vioget Philippe , Bonivento Massimiliano , Roulet Raymond , Vogel Pierre 
Published: December 2004

AbstractThe endocyclic double bond C(2), C(3) in 5,6‐dimethylidene‐7‐oxabicyclo[2.2.1]‐hept‐2‐ene (1) can he coordinated selectively on its exo‐face before complexation of the exocyclic s‐cis‐butadiene moiety. Irradiation of Ru3(CO)12 or Os3(CO)12 in the presence of 1 gave tetracarbonyl [(1R,2R, 3S,4S)‐2,3‐η‐(5,6‐dimethylidene‐7‐oxabicyclo[2.2.1]‐hept‐2‐ene)]ruthenium (6) or ‐osmium (8). Similarly, irradiation of Cr(CO)6 or W(CO)6 in the presence of 1 gave pentacarbonyl[(1R, 2R, 3S,4S)‐2,3‐η‐(5,6‐dimethylidene‐7‐oxabicyclo[2.2.1]hept‐2‐ene)]chromium (10) or ‐tungsten (11). Irradiation of complexes 6 and 11 in the presence of 1 led to further CO substitution giving bed‐tricarbonyl‐ae‐bis[(1R,2R,3S,4S)‐2,3‐η‐(5,6‐dimethylidene‐7‐oxabicyclo[2.2.1]hept‐2‐ene)]ruthenium (7) and trans‐tetracarbonyl[(1R,2R,3S,4S)‐2,3‐η‐(5,6‐dimethylidene‐7‐oxabicyclo‐[2.2.1]hept‐2‐ene)]tungsten (12), respectively. The diosmacyclobutane derivative cis‐m̈‐[(1R,3R,3S,4S)‐(5,6‐dimethylidene‐7‐oxabicyclo[2.2.1]hepta‐2,3‐diyl)]bis(tetracarbonyl‐osmium) (Os‐Os) (9) wa also obtained. The Diels‐Alder reactivity of the exocyclic s‐cis‐butadiene moiety in complexs 7 and 8 was found to be significantly higher than that of the free triene 1.
X‐Ray and 1H‐NMR Configurational Assignment of Valofan (α‐Allphanoyl‐α‐allyl‐γ‐valerolactone) Diastereoisomers
Authors: Lauterwein Jürgen , Alan Pinkerton J. , Wittekind H. Harald , Testa Bernard 
Published: December 2004

AbstractThe two diastereoisomers of valofan were separated by semi‐preparative HPLC. The preferred solution conformation of the two diastereoisomer was established by 1H‐NMR spectroscopy. The spectra could be interpreted in confirgurational terms. The configuration of the more lipophilic isomer was ascertained bty X‐ray crystallography as r‐2‐allophanoyl‐2‐allyl‐t‐4‐methylbutyrolactone.
‘Lone Pair’ and ‘CI Bond’ Ionization Energies of exo‐ and endo‐2‐Norbornyl Iodides
Authors: Honegger Evi , Heilbronner Edgar , Dratva Alfred , Grob Cyril A. 
Published: December 2004

AbstractA PE‐spectroscopic study of exo‐ and endo‐2‐norbornyl iodides suggests that the relative ability of the 2‐norbornyl group to stabilize an electron deficiency on a substituent X (e.g. I) in exo‐ or endo‐position depends on the location of the positive charge. There is no difference if the positive hole is strongly localized on on the substituent X (e.g. the 5p−1 state of the title compounds). On the other hand, our results indicate that teh positive hole semi‐localized in an exo‐CX bond is better stabilized by the 2‐norbornyl group than a semi‐localized, positive hole in an endo‐CX bond.
Electrochemical Synthesis of the Sex Attractant Pheromone of the Housefly: (Z)‐9‐Tricosene
Authors: Yadav Ashok K. , Tissot Paul 
Published: December 2004

AbstractThe electrochemical synthesis of muscalure, (Z)‐9‐tricosene(1), has been carried out by coelectrolysis of erucic acid (2) and propionic acid (3) in an undivided cell in methanol. To optimize the yield of the cross coupled product 1, the reaction has been studied in detail by varing different parameters, viz., electrode material, current density, molar ratio of 2 to 3, degree of partial neutralization and quantity of water in methanol.
γ‐Nitro‐γ‐butyrolacton
Authors: Kostova Kaline , Hesse Manfred 
Published: December 2004

γ‐Nitro‐γ‐butyrolactoneBy oxidation of 3‐(1‐nitro‐2‐oxocyclohexyl)propanal (1) with KMnO4, besides 3‐(1′‐nitro‐2′‐oxocyclohexyl)pripionic acid (2), the complete hydrolysis product 4‐oxononanedioic acid (4) and the oxidized semi‐hydrolysis product 5‐(2‐nitro‐5‐oxotetrahydro‐2‐furyl)pentanoic acid (3) were formed. The crystalline 3 decomposes at r.t. forming 4 and nitrous gases; its structure was established by X‐ray determination.
Synthesis, Structure, and Redox Chemistry of a Vitamin‐B12s‐Related Macrocyclic Complex of Cobalt(I)
Authors: Walder Lorenz , Rytz Gerhard , Vögeli Ulrich , Scheffold Rolf , Engel Peter 
Published: December 2004

Abstract(±)‐[1‐hydro‐8H‐HDP]cobalt(I) 1Full name of 1: [2,2,3,3,7,7,8,8,12,12,13,13,17,17,18,18,‐hexadecamethyl‐2,3,7,8,12,13,17,18,‐octahydro‐1H,23H‐10,20‐diaza‐porphinato]cobalt(I); full name of 2a: dibromo[2,2,3,3,7,7,8,8,12,12,13,13,17,17,18,18‐hexadecamethyl‐2,3,7,8,12,13,17,18‐octahydro‐1H,21H‐10,20‐diazaporphinato]cobalt(III).
For the nomenclature of [HDP]‐complexes see addendum in [2].
is obtained by chemical or electrochemical four‐electron reduction of (±)‐dibromo‐ or (±)‐dicano[1‐hydroxy‐8H‐HDP]cobalt(III) 2a or 2b4, respectively. The crystal nad molecular structure of 1 was determined by combination of X‐ray analysis and MS, 1H‐, and 13C‐NMR spectroscopy. Square‐planar coordinated Co(I) lies closely to the best plane through the four N‐atoms which form the first coordination sphere. Thermodynamic data for the coordination of axial bases with the cation of [1‐hydroxy‐8H‐HDP]cobalt 2 in its different metal oxidation states were determined. The pathway of the overall four‐electron reduction of 2a to 1 was elucidated: it involves a two‐electron reduction of the central metal, a two‐electron reduction of the macrocycle accompanied by elimination of the OH‐group and final protonation at C(1). Evidence for an intramolecular electron transfer between the central metal and the macrocycle is presented.
Komplementär diastereoselektive Cobalt‐Methylierungen des Vitamin‐B12‐Derivates «Cobester»
Authors: Kräutler Bernahard , Caderas Christian 
Published: December 2004

Complementary Diastereoselective Cobalt Methylations of the Vitamin‐B12 Derivative CobesterTreatment of heptamethyl cob(I)yrinate (2) in toluene/tetrahydrofurane (ca. 4:1) with methyl p‐toluenesulfonate under exclusion of O2 and with protection from light leads to the selective formation of the heptamethyl Coβ‐methylcob(III)yrinate (perchlorate 1b) in 75% yield. In contrast, methylation of 2 with methyl iodide under the same conditons results in the isomeric heptamethyl Coα‐methyulcob(III)yrinate (perchlorate 1a) in 73% yield, besides 7% of 1b. This complementary diastereoface‐selectivity of the methylation at the Co‐center results from alkylation under kinetic control and apparently involves two mechanistically distinct alkylation processes. A radical mechanism is considered to account for the stereochemically unusual outcome of the reaction with methyl iodide.
Bestimmung des Aggregationsgrads lithiumorganischer Verbindungen durch Kryoskopie in Tetrahydrofuran
Authors: Bauer Walter , Seebach Dieter 
Published: December 2004

Degree of Aggregation of Organolithium Compounds by Means of Cryoscopy in TetrahydrofuranThe association behaviour of alkyl‐, aryl‐ and alkinyl‐lithium compounds as well as of lithium enolates and chiral lithium azaenolates is determined from freezing‐point depression values in dilute tetrahydrofuran solutions at −108°C. Compared toX‐ray‐crystallographic data (lithiated methyldithiane, phenyllithium, lithio derivatives of a ketone, carboxylic amide and ‐ester, and a diketopiperazine‐bislactim‐ether), desaggregation is found under these conditions. The structures determined by 13C‐NMR spectroscopy for BuLi, lithiophenylacetylene and (t‐butyl)lithioacetylene are confirmed. The dilithio salt of a carboxylic acid is polymeric, a chiral lithio‐hydrazone and a chiral lithio‐oxazolidine are monomeric and dimeric, respectively. Lithium diisopropylamide is a monomer‐dimer equilibrium mixture. The apparatus described permits both synthesis and measurement of the reactive species under inert atmosphere conditions in the same vessel.
On the Nature of the 7‐Norbornadienyllithiums. Preliminary Communication
Authors: Goldstein Melvin J. , Wenzel Timothy T. 
Published: December 2004

AbstractLithium reductions of 7‐chloronorbornadiene and ofbis(7‐norbornadienyl)mercury both provide (C7H7)2Li2(5a). This product is accompanied by C7H7Li2Cl (5c) in the first case, and by C7H7Li (5b) in the second. The theoretically anticipated properties of all three organolithiums are apparent in the consistentCssymmetry of their hydrocarbon ligands, their protolytic destruction by 12‐crown‐4, and their significantJ(C(7), Li) (5a, 7.6;5b, 16.0;5c8.9 Hz).
Stabilities and Structures of Cu(II) Complexes with Linear Pentadentate Ligands by EPR Spectroscopy
Authors: Gampp Harald 
Published: December 2004

AbstractThe pH‐dependent equilibria between Cu(II) and the potentially pentadentate ligands 4,7,10‐triazatridecane‐1,13‐diamine (1) and 1,9bis(2‐hydroxyphenyl)‐2,5,8‐triazanonane (2) have been studied in aq. solution at 298 K by EPR titration. Each ligand forms complexes CuLHx (x=1,2,3) with strongly overlapping spectra. By using a recently developed algorithm, which does not need nay information with regard to the spectra of the species, stability constants and spectra were calculated from the EPR titration data. The anisotropic EPR spectra of the complexes were measured at 153 K and display axial or nearly axial symmetry (g∥ > g⊥) in each case. Based on the spectral parameters the assignment of the structures of the complexes was possible. With 1 and 2 the protonated complexes are equatorially coordinated, whereas in the fully deprotonated complexes an additional axial interaction occurs which is stronger with 2 than with 1.The results of this study show that EPR spectroscopy is a useful method for investigating equilibrium systems of Cu2+ even in complicated cases where minor species occur and where the individual spectra are unknown and strongly overlapping.
Inverted Hyperconjugation in Symmetrical 1,4‐Dihalocubanes
Authors: Honegger Evi , Heilbronner Edgar , Urbanek Thomas , Martin Hans‐Dieter 
Published: December 2004

AbstractThe σ‐orbital manifold of cubane 1, as suggested by its PE spectrum, is divided into two sets separated by a 3 eV gap extending from ∼ ‐10.5 eV to ∼ ‐13.5 eV. Halogen substituents with np AO basis energies falling into this gap (e.g. Cl or Br) will, therefore, hyperconjugate appreciably with both sets. Interaction with the lower‐lying set will lead to the usual destabilization (‘normal’ hyperconjugation), whereas interaction with the set above will necessarily lead to a ‘stabilization’ (‘inverted’ hyperconjugation). As a result the lone‐pair ionization energies of Cl or Br substituted cubanes (derived from PE spectra) are much larger than naively expected for an alkyl halide containing as much as 8 C‐atoms. In particular no significant shift of the e lone‐pair bands in the PE spectra of 1,4‐dichloro‐ and 1,4‐dibromocubane can be detected with respect to the first ionization energies of the free atoms Cl and Br, or of HCl and HBr.
Dimerisation of caffeine
Authors: Horman Ian , Dreux Bernard 
Published: December 2004

AbstractDisplacements of 1H‐NMR chemical shifs for caffeine in D2O solution as a function of concentration conform to the behaviour expected for pure dimer formation according to the equilibrium 2(caffeine)⇄(caffeine)2 with a statistical probability of at least 95%. Confidence limits reported earlier for the dimerisation constant of caffeine represent the real statistical dispersion in the experimental data and do not reflect a systematic error such as tetramer formation.
Umlagerungsreaktionen von (2′‐Propinyl)cyclohexadienolen und ‐semibenzolen
Authors: Lukáč Josef , Heimgartner Heinz 
Published: December 2004

Rearrangements of (2′‐Propinyl)cyclohexadienols and ‐semibenzenesThe acid‐catalyzed dienol‐benzene rearrangement of 3‐ and 5‐methyl‐substituted (2′‐propinyl)cyclohexadienols has been investigated. Treatment of the dienols with CF3COOH in CCl4 yields allenyl‐ and (2′‐propinyl)benzenes via [3,4]‐ and [1,2]‐sigmatropic rearrangements, respectively. The reaction with H2SO4 in Et2O leeds to a mixture of allenyl‐, 2′‐propinyl‐, 3′‐butinyl‐ and (2′,3′‐butadienyl)benzenes (Scheme 3). The latter are products of a thermal semibenzene‐benzene rearrangement (cf. Scheme 9). The corresponding semibenzenes have been prepared by dehydration of the cyclohexadienols with H2SO4 or POCl3 (Schemes 6 and 7). Under acidic conditions, the p‐(2′‐propinyl)semibenzenes 33–35 (Scheme 8) undergo [3,4]‐ and [1,2]‐sigmatropic rearrangements to give again allenyl‐ and (2′‐propinyl)benzenes, whereas the thermal rearrangements to the 3′‐butinyl‐ and (2′,3′‐butadienyl)benzenes (Scheme 9) involves a radical mechanism. In contrast, the o‐(2′‐propinyl)semibenzene b (Scheme 7) leads to (2′,3′‐butadienyl)benzene 32 via a thermal [3,3]‐sigmatropic rearrangement.
Synthese macrocyclischer Lactame aus Ketonen durch Ringerweiterung
Authors: Wälchli Rudolf , Bienz Stefan , Hesse Manfred 
Published: December 2004

Synthesis of Macrocyclic Lactams from Ketones by Ring Enlargement ReactionA general synthesis of N‐unsubstituted and N‐alkyllactams of general structure III is given. Starting materials for this conversion are the aldehydes of general structure I which, by reductive amination, are converted to the corresponding amines II. Under base catalysis, the ring enlargement II→III takes place (Scheme 3).
Planarisierung von tetrakoordiniertem Kohlenstoffatom. Synthese des überbrückten all‐cis‐[5.5.5.5]Fenestrans 13‐Oxapentacyclo[5.5.2.11.7.04,15.010,15] pentadecan‐14‐on
Authors: Pfenninger Armin , Roesle Alex , Keese Reinhart 
Published: December 2004

Planarisation of Tetracoordinate Carbon Atom, Synthesis of the Brigded all‐cis‐[5.5.5.5]Fenestrane 13‐Oxapentacyclo[5.5.2.11,7.04,15.010,15]pentadecan‐14‐oneThe synthesis of the ketolactone 23 from (Z,Z)‐1,5‐cyclooctadiene is reported. Transannular carben insertion, achieved via photolysis of the deprotonated (2,4,6‐trisisopropylphenylsulfonyl)hydrazone of 23 gives the bridged all‐cis‐[5.5.5.5]fenestrane 3.