bluuebunny/crossref_metadata_2025_split huggingface dataset:
Applications of ENDOR Spectroscopy to Radical Cations in Freon Matrices. Part 1. The radical cation of s‐trans‐buta‐1,3‐diene
Authors: Gerson Fabian , Qin Xue‐Zhi 
Published: December 2004

AbstractPrecise values of the proton coupling constants have been determined from the ENDOR spectra of the radical cation of s‐trans‐buta‐1,3‐diene generated from the neutral compound by γ irradiation in a CFCl3 matrix at 77 K. These values are 1.119 and 1.050 mT for the pairs of exo‐ and endo‐protons in the 1,4‐positions, respectively, and 0.283 mT for the pair of protons in the 2,3‐positions. A general TRIPLE resonance spectrum proves that all coupling constants have the same sign which should be negative by theory, Evidence by experiment and theory indicate that the s‐trans‐configuration of the neutral compound is retained upon ionization.
(Benzylthio)‐ und (Arylthio)‐substituierte Nitril‐ylide: Thermische Erzeugung und Reaktionen
Authors: Wipf Peter , Prevo Roland , Bieri Jost H. , Germain Gabriel , Heimgartner Heinz 
Published: December 2004

Thermal Generation and Reactions of (Benzylthio)‐and (Arylthio)‐Substituted Nitrile YlidesThermolysis of 4‐(benzylthio)‐ and 4‐(arylthio)‐1,3‐oxazol‐5(2H)‐ones 6, at 110–155° in the presence of dipolarophiles with activated C≡C, CC, CO, CS, and NN bonds, led to 5‐membered cyclo‐adducts and CO2 (cf. Schemes 3, 5‐7). Heating 6a and 6c in the presence of ethyl propiolate yielded ethyl quinoline‐3‐carboxylate (19) and ethyl pyridine‐3‐carboxylate(22), respectively (cf. Scheme 8). These results are rationalized on the basis of the intermediate formation of thio‐substituted nitrile ylides of type 7 (cf. Scheme 2), which undergo regioselective 1,3‐dipolar cycloadditions with reactive dipolarophiles. In the absence of such a dipolarophile, the nitrile ylides isomerize via a [1,4]‐H shift to give 2‐aza‐1,3‐butadienes of type 20. The latter are trapped in a Diels‐Alder reaction with ethyl propiolate (cf. Scheme 8).
The Reversible Proxibarbal‐Valofan Isomerisation. Part II. Kinetic studies in a biphasic octanol/water system
Authors: Wittekind H. Harald , Testa Bernard , Estreicher Jurek 
Published: December 2004

AbstractThe tautomerisation between proxibarbal (I) and the two diasterloisomers of valofan (IIX and IIY) was investigated at pH 7.4 in a biphasic octanol/H2O system. The rate constants of isomerisation and the equilibrium constants of (partition coefficients) were calculated by compartmental analysis. The rate constants of isomerisation were comparable with those determined in monophasic aqueous solutions, whereas at pH 7.4 and 37° the duration necessary for a global equilibrium to be reached was 4–6 times longer in the biphasic system. These reduced rates and the higher lipophilicity of IIX and IIY as compared to I may be of pharmacokinetic and pharmacodynamic significance. They may also have relevance for a number of drugs known or suspected to form lactonic or lactamic metabolites.
Die röntgenstrukturanalysen von (E)‐ und (Z)‐2‐Buten‐1,4‐diyl‐dithiocyanat bei 93 K
Authors: Belaj Ferdinand , Huber Stefan , Neier Reinhard 
Published: December 2004

The X‐Ray Diffraction Analysis of (E)‐ and (Z)‐2‐Butene‐1,4‐diyl DithiocyanateThe crystal structure of the (E)‐ and (Z)‐2‐butene‐1,4‐diyl dithiocyanate (1 and 2, respectively) which have been used as substrates for an E′ reaction, has been determined by X‐ray analysis. The SCN groups are for both molecules in an anticlinal conformation relative to the double bond. A remarkable intermoecular contact has been observed between the N‐atom of one molecule and the S‐atom of its neighbour.
Tandem Diels‐Alder Reactivity Controlled by Remote Substituents. Regioselective synthesis of linearly annellated six‐membered ring systems from (1RS,5SR,6RS,7SR)‐6,7‐bis(chloromethyl)‐8,9‐dimethylidene‐2‐oxabicyclo[3.2.2]nonan‐3‐one. Crystal structure of (1RS,5RS,6SR,11RS)‐6,7‐bis(chloromethyl)‐3‐oxo‐2‐oxatricyclo[7.4.0.1,5]tridec‐8‐en‐11‐yl methyl ketone
Authors: Demarchi Bernard , Vogel Pierre , Pinkerton Alan A. 
Published: December 2004

AbstractSynthess of 6,7,8,9‐tetramethylidene‐2‐oxabicyclo[3.2.2]nonan‐3‐one (12), 6,7,8,9‐tetramethylidene‐2‐azatricyclo[3.2.2]nonan‐3‐one (13), and (1RS,5SR,6RS,7SR)‐6,7‐bis(chloromethyl)‐8,9‐dimethylidene‐2‐oxabicyclo‐[3.2.2]nonan‐3‐one (14) are presented. The rate constants of the two successive Diels‐Alder additions of a given dienophile to 12 and 13 were nearly the same. Lewis‐acid‐catalyzed Diels‐Alder addition of methyl vinyl ketone to 14 gave adduct 39 with high regio‐ and stereoselectivity. Lewis acids isomerized 39 into(1RS,5RS,6SR,7SR,11RS)‐6,7‐bis(chloromethyl)‐3‐oxo‐2‐oxatricyclo[7.4.0.01,5]tridec‐8‐en‐11‐yl methyl ketone (40) whose structure was determined by single‐crystal X‐ray crystallography. Heating 39 with CsF/Cs2CO3 in DMF/HMPT gave (1RS,5RS,11RS)‐6,7‐dimethylidene‐3‐oxo‐2‐oxatricycl. [7.4.0.01,5]tridec‐8‐en‐11‐yl methyl ketone (42). The exocyclic butadiene moiety of triene 42 added to methyl propynoate and 2,3‐didehydroanisole with good regioselectivity giving polysubstituted anthracenyl and naphthacenyl derivatives, respectively.
Studies on the Biosynthesis of Iridals and Cycloiridals
Authors: Marner Franz‐Josef , Gladtke Dieter , Jaenicke Lothar 
Published: December 2004

AbstractThe incorporation of [2‐14C]acetate, [2‐14C]mevalonate, and [3H]squalene proved the squalenoid nature of the iridals, novel triterpenoids from rhizomes of swordlilies. Methionine is readily incorporated into cycloiridalls of Iris pallida dalmatica, thus indicating that the methylation of iridals via S‐adenosyl‐L‐methionine leads to the formation of the irone moiety of the bicyclic compounds. The 3H/14C ratio of the transferred labelled methyl group remained unchanged. Therefore, the methylation/cyclization of the terpenoid side chain of iridals must proceed by a concerted mechanism without formation of a cyclopropanoid intermediate.
Photocycloadditions of 2‐(trimethylsilyloxy)‐1,3‐butadiene to 2‐cycloalkenones. Access to the basic pentalenolactone skeleton
Authors: Demuth Martin , Pandey Bipin , Wietfeld Bernhard , Said Hadi , Viader José 
Published: December 2004

AbstractThe [2 + 2] Photocycloaddition of 2‐(trimethylsilyloxy)‐1,3‐butadiene to a number of 2‐cycloalkenones proved to be quite a general reaction leading to good yields of the cycloadducts (Table). This finding is surprising since dienes, in general, are better known as quenchers of enone triplets rather than as photochemical reactants. Both the high substrate concentrations, which can be employed in these cycloadditions, and the remarkable regio and stereoselectivity of the processes qualify them as valuable for syntheses. In a first application, the photoproducts 1a, b were transformed in three steps into a viable precursor 4 of the pentalenolactone‐G and ‐H antibiotics.
Reaktionen des Cumalinsäure‐methylesters und Cumalinaldehyds mit ambidenten Nucleophilen
Authors: Kvita Vratislav , Sauter Hanspeter , Tuck Brian 
Published: December 2004

Reactions of Methyl Coumalate and Coumalaldehyde with Ambident NucleophilesMethyl coumalate and coumalaldehyde show great diversity in their reactions with ambident nucleophiles both depending upon the 2H‐pyran‐2‐one derivative and the nature of the ambident nucleophile used. The products are either pyridine or pyrimidine derivatives.
Solid‐Phase Synthesis of Oligodeoxynucleotides containing phosphoramidate internucleotide linkages and their specific chemical cleavage
Authors: Bannwarth Willi 
Published: December 2004

AbstractOligonuclecotides bearing phosphoramidate internucleotide linkages can be prepared chemically by standard solid‐phase DNA synthesis. Thus, phosphoramidate internucleotide bonds can be placed at will into specific positions within a given DNA fragment. The backbone‐modified DNA fragments prepared in this way are susceptible to a specific chemical cleavage.
Struktur und Partialsynthese von dimerem Coleon F
Authors: Rüedi Peter 
Published: December 2004

Structure and Partial Synthesis of Dimeric Coleon FColeon F (1a), on standing in solution, slowly dimerizes to the labile C(7)‐epimeric spiro‐dihydrofuranes 2a/2b whose structures were elucidated by spectroscopic methods. Oxydative addition of 1a to another molecule of 1a in the presence of Fétizon's reagent rapidly yields 2a/2b, thus confirming their structures as (4bS,9RS,10′aS)4,4a,10′,10′a‐tetrahydro‐1′,6‐dihydroxy‐1,2,4a,7′,8′,10′a‐hexamethyl‐3′,7‐bis(2‐propenyl)‐spiro[3H,9H‐phenanthren‐9,5′‐5′H‐phenanthro[1,10‐bc]furan]‐2,3,5,8,9′‐pentone.
Syntheses of Amino‐dideoxyallose and Amino‐deoxyribose Derivatives Using Acylnitroso Dienophiles
Authors: Defoin Albert , Fritz Hans , Geffroy Guillaume , Streith Jacques 
Published: December 2004

AbstractThe dimethyl acetals 4 of (E)‐2,4‐pentadienal and of (E,E)‐ and (E,Z)‐2,4‐hexadienals undergo regio‐ and stereospecific cycloaddition reactions with in‐situ‐generated acylnitroso dienophiles 5a and 5b, leading thereby to the corresponding dihydrooxazines 7a–d and 8c–d. cis‐Glycolization of these latter adducts stereospecifically gave the dihydro derivatives 9a–d and 10d which, after sequential hydrogenolysis, deacetalization, and instant cyclization, led to the aminodeoxyribose derivatives 17a, 17f, and 18, and to the amino‐dideoxyallose compounds 17c and 17h. These piperidino‐deoxysugar derivatives exhibit a strong anomeric effect, i.e. OHC(1) is always axial, which is explained in terms of a nN(π)‐σ*(COH) orbital compression, as compared to the less pronounced one in the more classical pyranose series.
N‐(1,3‐Thiazol‐5(4H)‐yliden)amine aus 1,3‐dipolaren Cycloadditionen von Aziden mit 1,3‐Thiazol‐5(4H)‐thionen
Authors: Pekcan Sare , Heimgartner Heinz 
Published: December 2004

N‐(1,3‐Thiazol‐5(4H)‐ylidene)amines via 1,3‐Dipolar Cycloaddition of Azides and 1,3‐Thiazol‐5(4H)‐thionesOrganic azides 5 and 4,4‐dimethyl‐2‐phenyl‐1,3‐thiazol‐5(4H)‐thione (2) in toluene at 90° react to give the corresponding N‐(1,3‐thiazol‐5(4H)‐ylidene)amines (= 1,3‐thiazol‐5(4H)‐imines) 6 in good yield (Table). A reaction mechanism for the formation of these scarcely investigated thiazole derivatives is formulated in Scheme 3: 1,3‐Dipolar azide cycloaddition onto the CS group of 2 leads to the 1:1 adduct C. Successive elimination of N2 and S yields 6, probably via an intermediate thiaziridine E.
1,3‐Dipolare Cycloaddition aromatischer Nitril‐ylide und Nitril‐oxide an Dicyan und Diazocyanide
Authors: Ried Walter , Fulde Maria 
Published: December 2004

1,3 Dipolar Cycloaddition of Aromatic Nitrile Ylides and Nitrile Oxides with Cyanogen and DiazocyanidesNitril ylides 2 generated from the imidoyl chlorides 1 react with cyanogen and aryldiazocyanides to 2,5(4)‐dia‐ryl‐1H‐imidazole‐4(5)‐carbonitriles 3a,b or 5(4)‐(arylazo)‐2,4(5)‐diaryl‐1H‐imidazoles 4a and 2,3,5‐triaryl‐2,3‐dihydro‐1H‐1,2,4‐triazole‐1‐carbonitriles 5a–f, respectively (Scheme 1). Reactions of benzonitrile oxides 7 with these dipolarophiles lead to 3,3′‐diaryl‐5,5′‐bi[1,2,4]oxadiazoles 8a–c or 3‐aryl‐5‐(arylazo)‐1,2,4‐oxadiazoles 9a–j (Scheme 2).
(all‐E)‐12′‐Apozeaxanthinol, Persicaxanthine und Persicachrome
Authors: Märki‐Fischer Edith , Eugster Conrad Hans 
Published: December 2004

(all‐E)‐12′‐Apozeanthinol, Persicaxanthine, and PersicachromesReexamination of the so‐called ‘persicaxanthins’ and ‘persicachromes’, the fluorescent and polar C25‐apocarotenols from the flesh of cling peaches, led to the identification of the following components: (3R)‐12′‐apo‐β‐carotene‐3,12′‐diol (3), (3S,5R,8R, all‐E)‐ and (3S,5R,8S,all‐E)‐5,8‐epoxy‐5,8‐dihydro‐12′‐apo‐β‐carotene‐3,12′‐diols (4 and 5, resp.), (3S,5R,6S,all‐E)‐5,6‐epoxy‐5,6‐dihydro‐l2′‐apo‐β‐carotene‐3,12′‐diol =persicaxanthin; (6), (3S,5R,6S,9Z,13′Z)‐5,6‐dihydro‐12′apo‐β‐carotene‐3,12′‐diol (7; probable structure), (3S,5R,6S,15Z)‐5,6‐epoxy‐5,6‐dihydro‐12′‐apo‐β‐carotene‐3,12′‐diol (8), and (3S,5R,6S,13Z)‐5,6‐epoxy‐5,6‐dihydro‐12′‐apo‐β‐carotene‐3,12′‐diol (9). The (Z)‐isomers 7–9 are very labile and, after HPLC separation, isomerized predominantly to the (all‐E)‐isomer 6.
Potentiometric and spectrophotometric titration of Cu2+ complexes with N‐isopropyl‐2‐methyl‐1,2‐propanediamine
Authors: Kaderli Susan , Zuberbühler Andreas D. , Kansikas Jarno 
Published: December 2004

AbstractThe complexation of Cu2+ by N‐isopropyl‐2‐methyl‐1,2‐propanediamine (L) has been studied by potentiometric and spectrophotometric titration. The dominant complexes formed in this system are [CuL]2+, [CuL2]2+, [Cu2L2(OH)2]2+, and [CuL(OH)2]. The data were thoroughly tested for different models with [CuL(OH)]+, [CuL(OH)]+, [Cu(OH)]+, and [Cu2(OH)2]2+ as additional species. The importance of steric factors is indicated by the d‐d* spectra: for [CuL2]2+, (λmax = 499 nm) the absorption maximum is shifted by 50 nm to high energies relative to [Cu(en)2]2+, (λmax = 549 nm), whereas the opposite is true for the 1:1 complexes ([CuL]2+ : λmax = 712 nm,s [Cu(en)]2+ : λmax = 660 nm).
Conventional and Laser Photolysis of a Bisdiazo Compound
Authors: Hannemann Klaus , Wirz Jakob , Riesen Andreas 
Published: December 2004

AbstractEntirely different product distributions were observed when the bisdiazo compound 1 was irradiated by a conventional lamp (254 nm) on the one hand and by a pulsed excimer laser (248 nm) on the other. Continuous photolysis gave a complex reaction mixture (Scheme 2), of which eight products were identified. Pulsed laser photolysis gave (11E)‐dibenzocyclooctatriene 20 as a new product in 49% yield (Scheme 4). We postulate that compound 20 is formed via the biscarbene intermediate 18 which results from the sequential absorption of two photons by a single molecule within a single laser pulse.
Synthesis of Esters of 3‐(2‐Aminoethyl)‐1H‐indole‐2‐acetic Acid and 3‐(2‐aminoethyl)‐1H‐indole‐2‐malonic acid (= 2‐[3‐(2‐aminoethyl)‐1H‐indol‐2‐yl]propanedioic acid) 4th communication on indoles, indolenines, and indolines
Authors: Mahboobi Siavosh , Bernauer Karl 
Published: December 2004

AbstractAlkyl 3‐(2‐aminoethyl)‐1H‐indole‐2‐acetates 6a and 6b are synthesized starting from methyl 1H‐indole‐2‐acetate (2) via methyl 3‐(2‐nitroethenyl)‐1H‐indole‐2‐acetate (4) and the alkyl 3‐(2‐nitroethyl)‐1H‐indole‐2‐acetates 5a and (Scheme 1). Analogously, diisopropyl 3‐(2‐aminoethyl)‐1H‐indole‐2‐malonate 20b is obtained from diisopropyl 1H‐indole‐2‐malonate 11c (Scheme 4). An alternative synthesis of 20a and 20b follows a route via 15–18 and the dialkyl 3‐(2‐azidoethyl)‐1H‐indole‐2‐malonates 19a and 19b, respectively (Scheme 3). The aminoethyl compounds 6a and 20a are easily transformed into lactams 7 and 21, respectively. Procedures for the preparation of the indoles 2 and 11a and of the alkylating agent 14 are described. A tautomer 12 of 11a is isolated.
Generation and Trapping of Triafulvene
Authors: Weber Andreas , Stämpfli Urs , Neuenschwander Markus 
Published: December 2004

AbstractSubstituted methylidenecyclopropanes 12a–d, being easily available from 1,1‐dibromo‐2‐(phenylthio)‐cyclopropane (9a), are attractive precursors of triafulvene (2‐methylidene‐1‐cyclopropene; 1). Both the sulfoxide 12b and the sulfone 12c react with an excess of alkoxides (t‐BuOK and NaOMe) to give 12e and 12f, respectively, while the sulfinyl group of 12b may be replaced by the PhCH2S substituent in the presence of PhCH2SH/t‐BuOK. These reactions (Scheme 4) may be explained by assuming 1 as a reactive intermediate, although an alternative sequence including carbene 20 (Scheme 6) is not completely ruled out. D‐labelling experiments (Scheme 5) do not give conclusive evidence due to D scrambling, but deprotonation/methylation sequences show that HC(2) of 12a–c is the most acidic proton. Final evidence for 1 results from the reaction of 12d with cyclopentadienide (Scheme 7): the reaction of 1 with cyclopentadiene produces the expected [4 + 2]‐cycloaddition product 23, while some mechanistic insight results from the sequence 12d → 24 → 25.
Cyclization Studies with N‐Mannich bases of 2‐substituted indoles
Authors: Burger Ulrich , Bringhen Alain O. 
Published: December 2004

AbstractThe synthesis of the indoles 7, 15, 16 with a 3‐methoxyphenyl group, attached via an α‐side chain of 1,2,or 3 CH2 units, is reported. These compounds, after appropriate protection at C(3), were transformed into the N‐[(dimethylamino)methyl]indoles 22, 23, and 24, respectively. When treated with AcCl, these N‐Mannich bases gave, in two cases, stable N‐(chloromethyl)indoles 25 and 26. In the presence of SnCl4, ring closure occurred via electrophilic attack of 1‐methylideneindolium ions on the methoxyphenyl group. Formation of seven‐membered rings (→ 27, 28) and eight‐membered rings (→ 29) was found to be a favorable process. Cyclization to six‐membered rings did not occur within this series.
Polynuclear Iron and Rhodium Complexes of 7‐Oxa[2.2.1]hericene (2,3,5,6‐tetramethylidenebicyclo[2.2.1]heptan‐7‐one)
Authors: Rubello Albino , Vogel Pierre 
Published: December 2004

Abstractμ‐Carbonyl(RhRh)di(η5‐indenyl)[(2R,3S)‐C,2,3,C‐η‐(2,3,4,5‐tetramethylidenebicyclo[2.2.1]heptan‐7‐one)]]‐dirhodium(I)(RhRh) (7) and cis‐μ‐[(2R,3S,5R,6S))‐C,2,3,C‐η:C,5,6,C‐η‐(2,3,5,6‐tetramethylidenebicyclo[2.2.1]heptan‐7‐one)]bis[μ‐carbonyldi(η5‐indenyl)dirhodium(I)(RhRh)] (8) have been prepared. Complex 7 reacts with Fe2(CO)9 in hexane/MeOH and gives cis‐μ‐[(2R,3S,5R,6S] (9), trans‐μ‐[(2R,3S,5S,6R)‐C,2,3,C‐η: C,5,6, C‐η‐(2,3,5,6‐tetramethylidenebicyclo[2.2.1]heptan‐7‐one)‐μ‐carbonyldi(η5‐indenyl)dirhodium(I)(RhRh)‐(tricarbonyliron) (10), and, μ‐carbonyl(RhRh)[(2R,3S)‐C,2,3,C‐η‐(2,3‐dimethyl‐5,6‐dimethylidenebicyclo‐[2.2.1]hept‐2‐en‐7‐one)]di(η5‐indenyl)dirhodium(I)(RhRh) (11). Treatment of 7‐oxa[2.2.1]hericene (4) with Fe2(CO)9 or (cyclooctene)2Fe(CO)3 gave a 1:2 mixture of cis‐μ‐[(2R,3S,5R,6S)‐] (12) and trans‐μ‐[(2R,3S,5S,6R)‐C,2,3,C‐η:C,5,6,C‐η‐(2,3,5,6‐tetramethylidenebicyclo[2.2.1]heptan‐7‐one)]bis(tricarbonyliron)(13).
1,5,7‐Triazabicyclo[4.4.0]dec‐5‐en als Reaktionsmedium: Präparativ ergiebige einstufige Herstellung von Etioporphyrin aus Protoporphyrin
Authors: Kämpfen Ulrich , Eschenmoser Albert 
Published: December 2004

1,5,7‐Triazabicyclo[4.4.0]dec‐5‐ene as Reaction Medium: An Efficient One‐Step Formation of Etioporphyrine from ProtoporphyrineHeating the commercially available protoporphyrine (4) in molten 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD) at 200° for 4 h under exclusion of O2 produces etioporphyrine (6) in 60–70% yield by bisdecarboxylation and concomitant reduction of the two vinyl groups. Mesoporphyrine (5) is bisdecarboxylated to 6 in over 80% yield under these conditions in TBD as well as in DBU as the reaction medium.
Spectroscopic Studies of Cyclometallated Pd(II) and Pt(II) Complexes: Optical absorption and emission of single crystals of [Pd(thpy)2] and [Pt(thpy)2]
Authors: Schwarz Raimund , Gliemann Günter , Chassot Laurent , Jolliet Philippe , von Zelewsky Alex 
Published: December 2004

AbstractThe polarized optical absorption and emission (spectra, decay times) of single crystals of [Pd(thpy)2] and [Pt(thpy)2] (thpy ≡ C(3′)‐deprotonated form of 2‐(2‐thienyl)pyridine) at temperatures 1.9 K ⩽ T ⩽ 80 K are reported. The emission of [Pt(thpy)2] can be influenced strongly by applied magnetic fields (0 ⩽ H ⩽ 6 T). Depending on the central ions Pd and Pt, the lowest excited electronic states of the single complexes are ligand‐centered (LC) states and metal‐to‐ligand charge transfer (MLCT) states, respectively. This difference leads to distinctly dissimilar properties of the emission of both compounds. The experimental data show that the emission of single crystals of [Pd(thpy)2] and [Pt(thpy)2] at T ⩽ 30 K originates from several types of traps (defect states of symmetry 3B2−stabilized below the exciton band) with LC and MLCT character, respectively. In the Pt compound, the 3B2 is split by spin‐orbit coupling into three states. The states B and A, which determine the emission properties, are separated by Δv ∼ 13 cm−1. Both states can mix under the influence of an applied magnetic field yielding an increase of the emission intensity by a factor of ∼ 1.5 at H = 6 T.
Stereochemical Criteria Providing Unambiguous Experimental Evidence for the intermediacy of ion/molecule complexes in the generation of enolates from gaseous alkoxides. Short communication
Authors: Sülzle Detlev , Schwarz Helmut 
Published: December 2004

AbstractThe epimeric alkoxides 6a and 6b, generated in the gas phase by deprotonation of the stereospecifically deuterated isoborneols 5a and 5b, undergo loss of H2 and HD in a 1:1 ratio. This result, ruling out a concerted one‐step process, establishes the intermediacy of an ion/molecular complex (‘solvated’ hydride ion) in the course of formation of enolates from the alkoxide anions in the gas phase.
Diels‐Alder‐Reaktionen mit 3‐Cyclopropylidenprop‐1‐enyl‐ethyl‐ether als 1,3‐Dien
Authors: Kienzle Frank , Stadlwieser Josef , Mergelsherg Ingrid 
Published: December 2004

Diels‐Alder Reactions with 3‐Cyclopropylideneprop‐1‐enyl Ethyl Ether as 1,3‐DieneThe title compound undergoes readily Diels‐Alder reactions with various dienophiles, especially with quinones. The resulting adducts constitute key intermediates in the synthesis of labdane diterpenoids.
The Radical Cations of Bicyclo[2.2.1]hepta‐2,5‐diene (8,9,10‐Trinorborna‐2,5‐diene) and bicyclo[2.2.2]octa‐2,5‐diene (2,3‐Dihydrobarrelene). An ESR and ENDOR study
Authors: Gerson Fabian , Qin Xue‐Zhi 
Published: December 2004

AbstractThe radical cation of bicyclo[2‐2.1]hepta‐2,5‐diene (8,9,10‐trinorborna‐2,5‐diene; 1) in CF2ClCFCl2, and CF3CCl3 matrices and that of bicyclo[2.2.2]octa‐2,5‐diene (2,3‐dihydrobarrelene; 2) in CFCl3 and CF3CCl3 matrices have been studied by ESR and ENDOR spectroscopy. For \documentclass{article}\pagestyle{empty}\begin{document}${\bf 1}^{+ \atop \dot{}}$\end{document}, the coupling constants of the olefinic, methano‐bridge, and bridgehead protons are −0.780 ±0.005, +0.304±0.002, and −0.049±0.002 mT, respectively. The hyperfine tensor for the methano‐bridge protons is axial, Ax = +0.263 ± 0.002 and Ay = +0.386 ± 0.002 mT, while that for the olefinic protons is orthorhombic, Ax = −0.594 ± 0.005, Ay= −0.913 ± 0.005, and Az = −0.834 ± 0.005 mT (x parallel to CH‐ z parallel to 2pπ axis). For \documentclass{article}\pagestyle{empty}\begin{document}${\bf 2}^{+ \atop \dot{}}$\end{document}, the coupling constants of the olefinic, ethano‐bridge, and bridgehead protons are −0.68 ± 0.01, +0.162 ± 0.005, and −0.108 ± 0.005 mT, respectively. The hyperfine data for \documentclass{article}\pagestyle{empty}\begin{document}${\bf 1}^{+ \atop \dot{}}$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}${\bf 2}^{+ \atop \dot{}}$\end{document} fully support the presentation of their singly occupied orbitals as antisymmetric combinations, b2(π), of the two bonding ethene π‐MO's.
The Allylic Oxidation of Geraniol Catalyzed by Cytochrome P‐450Cath., Proceeding with retention of configuration
Authors: Fretz Heinz , Woggon Wolf‐Dietrich , Voges Rolf 
Published: December 2004

AbstractIncubation of the geraniols (R)‐(8‐2H1)[8‐3H1]‐1 and (S)‐(8‐2H1)[8‐3H1]‐1 with microsomal cytochrome P‐450Cath. from the subtropical plant Catharanthus roseus (L.)G. DON resulted in the formation of the chiral 8‐hydroxygeraniols (S)‐(8‐2H1)[8‐3H1]‐2 and (R)‐(8‐2H1)[8‐3H1]‐2. Their absolute configuration was assigned on the basis of the 1H‐decoupled 3H‐NMR Spectra of the corresponding dicamphanates (S)‐(8‐2H1)[8‐3H1]‐9 and (R)‐(8‐2H1)[8‐3H1]‐9, of which the configurations are established in relation to the synthetic reference samples. The results clearly indicate retention of configuration during the allylic oxidation of 1.