bluuebunny/crossref_metadata_2025 huggingface dataset:
Enamines. II. A theoretical and photoelectron spectroscopic study of the molecular and electronic structures of aliphatic enamines
Authors: Müller Klaus , Previdoli Felix , Desilvestro Hans
Published: December 2004

Comparison of PE. spectroscopic data for four series of enamines (including azetidine and some aziridine derivatives) for studying the influence of amine‐ring size on electronic structure show the pyrrolidino group to exhibit the strongest amine/double bond coupling in sterically unconstrained enamines. However, the azetidino group accommodates best steric congestion due to dialkyl substitution at the β‐position of the enamine unit. Quantum‐chemical calculations of equilibrium structures and energy profiles for amine rotations in model enamines by the PRDDO SCF method agree satisfactorily with experimental results. Notable exceptions are pyrrolidine derivatives for which PRDDO overestimates the amount of N‐pyramidality.
Activated C,H‐Acids: N‐Alkyl‐9‐fluorenimines. Preliminary communication
Authors: Bradamante Silvia , Colombo Silvana , Pagani Giorgio A. , Roelens Stefano
Published: December 2004

N‐Substituted 9‐fluorenimines 1 are easily prepared from primary amines or aminoesters and 9‐fluorenimine: their conjugate carbanions 2 are formed by the action of alkoxides and are reprotonated to 1 or to the tautomeric 9‐alkylidenamino‐fluorenes 3 depending upon substituents.
Synthesis of L‐α‐aminoadipyl‐L‐serinyl‐D‐valine, a naturally occuring tripeptide from the fermentation of Penicillium chrysogenum
Authors: Shields James E. , Campbell Charles S. , Scott Doyle K. , Miller Roger D. , Neuss Norbert
Published: December 2004

A new tripeptide, L‐α‐aminoadipyl‐L‐seryl‐D‐valine has been synthesized by coupling the protected L‐seryl‐D‐valine dipeptide with an appropriately protected L‐α‐aminoadipic acid ester. The free tripeptide was obtained after treatment with liquid HF and purification by HPLC.
A Convergent Synthesis of (±)‐α‐ and β‐Himachalenes
Authors: Oppolzer Wolfgang , Snowden Roger L.
Published: December 2004

(±)‐α and β‐Himachalene, 5 and 6, have been synthesized in a convergent manner from 3,3‐dimethylacrolein (9), the ester enolate 10 and the silyloxypentadienyllithium 7. The key steps are the regioselective γ‐addition of the dienal 13 to 7 and the intramolecular Diels‐Alder addition 15 → 16. Hydrogenolysis of the diethylphosphate group and functionalization at C (5) completed the synthesis of 5 and 6.
Crystallographic and Spectroscopic Evidence for an Intramolecular (OH … π)‐Interaction
Authors: Bernd Schweizer W. , Dunitz Jack D. , Pfund Rolland A. , Ramos Tombo Gerardo M. , Ganter Camille
Published: December 2004

Crystallographic and spectroscopic evidence for an intramolecular (OH … π)‐interaction in anti9,10‐10endo‐hydroxy, 10exo‐butyltricyclo [4.2.1.12.5]deca‐3, 7‐dien‐9‐one (1) is presented.
Nafion‐TMS‐ and TMS‐Trifluoroacetate‐Induced Rearrangements of Cyclopropyl Ketones ‐ A procedure for the regioselective conversion of semibullvalenes to barrelenes
Authors: Demuth Martin , Mikhail Gamal , George Manapurathu V.
Published: December 2004

Trimethylsilyl trifluoroacetate (TMSTFA) and the polymer‐supported sulfonate Nafion‐TMS exhibit selective reaction modes in the opening of cyclopropyl ketones. The yields are generally high. Nafion‐TMS rearranges the tricyclooctanones 1a and 1b to the bicyclooctenones 4a and 4b (while TMSTFA gives ring‐opened adducts 6a,b) with high regioselectivity. Aro‐semibullvalenes (8a, 14, 17a,b) are efficiently rearranged to arobarrelenes (7a, 13, 20a,b) by both reagents. The latter rearrangements have also been achieved in mixtures of trifluoroacetic acid and tetramethylsilane (TMS), where the acid combines with an unidentified impurity of commercial TMS to form a strong electrophilic agent. The electrophile‐assisted rearrangement of the naphtho‐semibullvalenes 14a+b resulted in conversion to the naphthobarrelenes 13a+b with the opposite regioselectivity to that observed for the thermal equilibration at 220°.
1H‐ und 13C‐NMR.‐Spektroskopie der Nonadride
Authors: Nieminen Sirkku , Tamm Christoph
Published: December 2004

1H‐ and 13C‐NMR. Spectroscopy of the Nonadrides

The 1H‐ and 13C‐NMR. spectra of the nonadrides glaucanic acid (1), glauconic acid (2), heveadride (3), byssochlamic acid (4), scytalidin (5), rubratoxin A (6), and rubratoxin B (7) have been measured. Partial decoupling experiments permitted assignment of the majority of the signals.
The Effect of Solvent on Competing Hydroperoxide and Dioxetane Formation on Photo‐Sensitized Oxygenation of Olefins
Authors: Jefford Charles W. , Kohmoto Shigeo
Published: December 2004

The rates of the competitive photo‐sensitized oxygenation of 2‐isobutylideneadamantane (1) and 2‐propylidene‐adamantane (2) with 1, 1‐di‐t‐butyl‐2‐methoxyethane (3) in various solvents were determined. The rates for 1 and 2 were independent of solvent, whereas that for 3 varied markedly with solvent polarity. Compounds 1 and 2 gave only hydroperoxides while 3 gave dioxetane. These results are interpreted in terms of two competing processes involving little and much charge separation leading to hydroperoxide and dioxetane, respectively.
Synthese makrocyclischer Lactone durch Ringerweiterung. Vorläufige Mitteilung
Authors: Kostova Kalina , Lorenzi‐Riatsch Annalaura , Nakashita Yoshihiko , Hesse Manfred
Published: December 2004

Synthesis of Macrocyclic Lactones by Ring Enlargement Reaction

Treatment of 3‐(1‐nitro‐2‐oxocyclohexyl)propanal (1) prepared by Michael addition of 2‐nitrocyclohexanon and acrylaldehyde with methyltri (2‐propoxy)tita‐nium yielded a mixture of 2 and 3 which was converted into 6‐nitro‐9‐decanolide (4).
Synthese von (+)‐(5S, 6S)‐Azafrin‐methylester; absolute Konfiguration von Aeginetinsäure and von weiteren vicinalen Apocarotin‐diolen
Authors: Eschenmoser Walter , Uebelhart Peter , Eugster Conrad Hans
Published: December 2004

Synthesis of (+)‐(5S, 6S)‐Azafrin Methyl Ester; Absolute Configuration of Aeginetic Acid and of Further Vicinal Apocarotenediols

We describe the synthesis of a series of optically active vicinal apo‐β‐carotenediols. Thus, starting from (+)‐(5S, 6S)‐5,6‐dihydroxy‐5,6‐dihydro‐β‐ionone (2) we have prepared the (Z/E)‐isomeric (+)‐C15‐esters 7 and 8, the (+)‐retinoic derivatives 14, 15, 18, 19 and (+)‐methyl azafrinate (22), the enantiomer of the naturally occur‐ring compound (s. Scheme 1). Our synthesis also establishes the absolute configura‐tion of aeginetic acid (24), aeginetoside (25) and aeginetin (26), compounds isolated from the root parasite Aeginetia indica by Indian and Japanese workers (s. Scheme 2).

The presented synthesis of optically active methyl azafrinate confirms our previous assignment [14] of the absolute configuration of azafrin (1a), which was based on degradative evidence.
Synthesis of Methyl 2‐Acetamido‐4,6‐di‐O‐acetyl‐3‐S‐acetyl‐2‐deoxy‐3‐thio‐α‐D‐mannopyranoside
Authors: Miljković Momčilo , Hagel Peter
Published: December 2004

Methyl‐2‐acetamido‐4,6‐di‐O‐acetyl‐3‐S‐acetyl‐2‐deoxy‐3‐thio‐α‐D‐mannopy‐ranoside has been synthesized by conversion of methyl 2‐amino‐2‐deoxy‐4,6‐O‐benzylidene‐α‐D‐altropyranoside into the corresponding 3‐O‐methanesulfony1‐2‐N‐[(methylthio)thiocarbonyl]derivative followed by intramolecular displacement of the 3‐O‐methanesulfonyloxy group with the (methylthio)thiocarbamoyl group.
Variable temperature multinuclear NMR. Investigation of dimethylformamide exchange on the octakis (N,N‐dimethylformamide)‐thulium(III) ion
Authors: Pisaniello Dino L. , Merbach André E.
Published: December 2004

The rate of DMF exchange on [Tm (DMF)8]3+ has been determined by 1H‐ and 13C‐NMR. linebroadening techniques. 1H‐NMR. yields the following solvent exchange parameters; ΔH* = 33.2 (±0.5) kJ mol−1, ΔS* = 9.9 (±2.4) J K−1 mol−1and k (200 K) = 2.94 (±0.09)× 104 s−1, whilst results from 13C‐NMR. are similar. No evidence, by 35C1‐NMR., was found of contact ion‐pair formation when the perchlorate salts were used.
Structures cristallines et moléculaires des muses macrocycliques. II. La trans‐civettone et sa 2,4‐dinitrophénylhydrazone
Authors: Bernardinelli Gerald , Gerdil Raymond
Published: December 2004

Crystal and Molecular Structure of Macrocyclic MUSKS. II. trans‐Civetone and its 2, 4‐Dinitrophenylhydrazone

The trans and cis isomers of civetone (C17H30O) crystallize in isomorphous systems and form plastic crystals (tetragonal, space group I41 a=9.95 (4), c = 32.79 (1) Å, Z = 8). Mixed crystals were prepared with cis‐civetone as second component. Accordingly the diffuse structural model obtained for the disordered phase of the cis‐isomer [1] is also regarded as representative of that of trans‐civetone.

The crystal structure of trans‐civetone 2,4‐dinitrophenylhydrazone (DNPHTC; C23H34N4, Monoclinic, Space group P21/c, a=8.364(2), b=7.971(1), c=36.025(8) Å, β=91.44 (2)°) was solved by direct methods and refined to a final R of 0.09 (Rw = 0.021). The macrocycle adopts a sexangular conformation [23*434*44*], and its mean plane is approximatively perpendicular to that of the aromatic substituent. Empirical force field calculations have shown that the DNPH substituent has very little influence on the macrocycle conformation. The intermolecular interactions take place essentially between groups of the same type: macrocycle…macrocycle and DNPH…DNPH.
Formation and dissociation mechanism of amide complexes. V. Interconversion of dimeric and monomeric Cu2+‐complexes with 1,8‐diamino‐3,6‐diaza‐2,7‐octanedione: Comparison between the reactivity of terminal and internal amide groups
Authors: Zuberbühler Andreas D. , Kaden Thomas A.
Published: December 2004

The protonation and deprotonation rates of the coordinated amide groups in the Cu2+‐complexes of 1,8‐diamino‐3,6‐diaza‐2,7‐octanedione (DED = L) have been studied by stopped‐flow techniques. Starting at low pH from Cu2+ and DED the dimeric Cu2L24+‐complex, fully formed within the mixing time of the stopped‐flow instrument, reacts in two consecutive steps to yield the final product CuLH−2. The rate constants of the forward and backward reactions have been determined and are given in Table 1. The intermediate was identified as Cu2L2H−22+ by measuring its VIS.‐absorption spectrum.

The rate constants for the interconversion of the amide groups from the O‐ to the N‐coordinated form in the Cu2+‐complexes of DED, 2,10‐dioxo‐1, 4, 8, 11 tetraazaundecane (DANA) and triglycine (TRIGLY) are compared with each other. It is shown that these rate constants are similar, no matter whether the amide group is terminal or internal as long as the rotation is easily possible as is the case in the dimeric species Cu2L24+ and Cu2L2H−22+. However, for CuLH−2 the inter‐conversion only takes place after opening of one of the chelate rings in a rapid protonation preequilibrium.
Herstellung der 1H‐Indazole durch Photolyse von 2‐Aminophenylketon‐O‐(äthoxycarbonyl)oximen und von 3,1,4‐Benzoxadiazepin‐2 (1H)‐onen
Authors: Pfoertner Karl‐Heinz , Foricher Joseph
Published: December 2004

1H‐Indazoles Obtained by Photolysis of 2‐Aminophenylketon‐O‐(ethoxycarbonyl)oximes and of 3, 1, 4‐Benzoxadiazepine‐2(1 H)‐ones

Irradiation of (E)‐ and (Z)‐O‐(ethoxycarbonyl)oximes 1 of 2‐aminophenyl ketones in solution with UV, and/or visible light gives 1 H‐indazole derivatives 2 in high yields (Scheme 1). For this reaction the amino group must be un‐ or mono substituted. With the N, N‐disubstituted (E)‐1d (Scheme 2) no 1 H‐indazole formation is observed, because the radicals formed by its photolysis react in an unspecific manner with each other and with the solvent. From the behaviour of (E)‐1d and from the lack of any E/Z‐isomerization of 1 we conclude that the photoreaction starts with a splitting of the N, O‐bond in two separate radicals, whereas the radical pair produced by the also studied photolysis of 3,1,4‐benzoxadiazepine‐2(1 H)‐one derivatives 3 is fixed in the parent molecule, and therefore tends to recombine.

This makes a prolonged irradiation necessary to convert the benzoxadiazepinones 3 into the 1 H‐indazoles 2. The different reaction rates of the (E) and (Z)‐isomers of 1 (provided R4 = H) are understood by means of different intramolecular H‐bridges.
13C‐NMR. Spectra of Natural and Semi‐synthetic Cannabinoids
Authors: Binder Michael , Franke Ingo , Schmidt Burkhard , Dietrich Wolfgang
Published: December 2004

The 13C‐NMR. spectra of one natural and ten semi‐synthetic cannabinoids were analyzed in detail. Assignments of the signals are based on their chemical shifts, splitting patterns in 1H‐off‐resonance decoupling experiments and comparison with 13C‐NMR. data of related cannabinoids. With some compounds final assignments were made by selective 1H‐decoupling experiments and incremental calculations.
Technische Verfahren zur Synthese von Carotinoiden und verwandten Verbindungen aus 6‐Oxo‐isophoron. VII. Synthese von Rhodoxanthin und (3RS,3RS)‐Zeaxanthin aus der C15‐Ringkomponente
Authors: Widmer Erich , Zell Reinhard , Grass Hansjörg , Marbet Roman
Published: December 2004

Technical Procedures for the Synthesis of Carotenoids and Related Compounds from 6‐Oxo‐isophorone. VII. Synthesis of Rhodoxanthin and (3RS,3RS)‐Zeaxanthin from the C15‐Ring Component1

An efficient 7‐step synthesis of (3RS,3RS)‐zeaxanthin (3) in 20% overall yield starting from 6‐oxo‐isophorone (7) is described. Intermediates are 6,6′‐dihydro‐rhodoxanthin (4) and rhodoxanthin (1), which are now accessible in 4 and 5 steps, and 45 and 25% overall yield, respectively. Novel methods for the simultaneous removal of the hydroxy group and the partial reduction of the triple bond of a monoalkynylated 1,4‐dioxo‐2‐ene system have been developed.
Cyclometalation of arylazo compounds. Part 2Regioselectivity of the Cyclopalladation of Some Substituted 1‐Arylazonaphthalenes. 2nd Communication on Compounds with a Metal‐Arene σ‐Bond
Authors: Hugentobler Max , Klaus Alfred J. , Mettler Hanspeter , Rys Paul , Wehrle Gabi
Published: December 2004

A variety of cyclopalladated 1‐arylazonaphthalenes is described, where ortho‐palladation occurs at C(2) in the naphthyl ring or at C(2′ or 6′) in the phenyl moiety. Two examples of Peri‐cyclopalladation at C(8) in the naphthyl ring are presented. The electronic and steric‐influences of substituents at either arene moiety on the relative basicities of the azo‐N‐atoms and the relative nucleophilicities of the potential palladation sites C(2), C(2′ or 6′), and C(8) are discussed qualitatively in order to rationalize the observed regioselectivity.
The Synthesis of Hetero‐Halogenated Derivatives of Phloroglucide Analogues[1]
Authors: Moshfegh Ali Akbar , Mazandarani Behnaz , Nahid Azarmidokht , Hakimelahi Gholam Hosein
Published: December 2004

A short synthesis of the title compounds is reported. Most of the compounds prepared were found to be active against a number of pathogenic microorganisms in vitro.
Polar Effects. X. Polar Substituent Effects in the Solvolysis of 3‐Substituted 1‐Adamantyl Bromides and Toluenesulfonates
Authors: Grob Cyril A. , Schaub Bruno
Published: December 2004

The rate constants for 3‐substituted adamantyl p‐toluenesulfonates 3a‐3k in ethanol/water 80:20 correlate well with the respective inductive substituent constants σ. The reaction constant ρ for the toluenesulfonates 3 is 10% larger than for the corresponding bromides 2, indicating somewhat more charge separation in the activation of the toluenesulfonates. Evidence is presented that stabilization of the resultant 1‐adamantyl cations by induction involves graded 1,3‐bridging, which is favored when the substituent is an electrofugal group, and that stabilization by n‐electron donors involves C, C‐hyperconjugation. Rate ratios for the toluenesulfonates 3 and the bromides 1 exceed 103 and are almost independent of the 3‐substituents. The implications of this are discussed in the light of current hypotheses.
Rapid Silylation of a Glass Surface: Choice of Reagent and Effect of Experimental Parameters on Hydrophobicity
Authors: Deyhimi Farzad , Coles Jonathan A.
Published: December 2004

The silylation of the surface of sodium borosilicate glass was investigated under conditions that might be applied to the fabrication of ion‐selective microelectrodes of the liquid membrane type such as are used in physiology, Silylation was carried out for 15 min at different temperatures and with six different silanes. The hydrophobicity was measured and found to be greatest with reaction temperatures of 200–350°, the effectiveness of the different silylating agents being in the (increasing) order: trimethylchlorosilane, tributylchlorosilane, (dimethylamino)trimethylsilane, hexamethyldisilazane, dimethyldichlorosilane, bis(dimethylamino)dimethylsilane. The results give evidence of a catalytic effect of basic amine groups and show that the reactivity of the surface of freshly drawn glass is increased by acid leaching.
1‐p‐Menthene‐8‐thiol: A powerful flavor impact constituent of grapefruit juice (Citrus parodisi MACFAYDEN)
Authors: Demole Edouard , Enggist Paul , Ohloff Günther
Published: December 2004

1‐p‐Menthene‐8‐thiol (B) is shown to be a potent character‐donating constituent of grapefruit juice, in which it occurs at the ppb‐level or below. A convenient synthesis is described for this terpene‐thiol, apparently the most powerful flavor compound ever found in nature.
Structural Factors Affecting the Basicity of ω‐Pyridylalkanols, ω‐Pyridylalkanamides and ω‐Pyridylalkylamines
Authors: Mayer Joachim M. , Testa Bernard
Published: December 2004

The present paper describes the preparation by conventional methods (when not available commercially) and the pKa‐determination of the α‐, β‐ and γ‐isomers of pyridylethanamide, 3‐pyridylpropanamide. 4‐pyridylbutanamide, 5‐pyridyl‐pentanamide, pyridylmethanol, 2‐pyridylethanol, 3‐pyridylpropanol, 4‐pyridyl‐butanol, 5‐pyridylpentanol, pyridylmethylamine, 2‐pyridylethylamine, 3‐pyridyl‐propylamine, 4‐pyridylbutylamine, and 5‐pyridylpentylamine. While a field effect accounts for many variations in pKa as a function of chain length, marked inductive effects are operative in some methyl and ethyl homologs. The pKa‐decreasing influence of an intramolecular H‐bond is also apparent in some lower homologs belonging to the α‐series.
A New Type of Photorearrangement of γ‐Hydroxy‐α, β, δ, ε‐dienone
Authors: Katsumura Shigeo , Isoe Sachihiko
Published: December 2004

A new type of photorearrangement of the γ‐hydroxy‐α, β, δ, ε‐dienone, vomifoliol acetate (2) to the diketone 4 is described, and its facile rearrangement is compared with that of desoxyvomifoliol acetate (3).
Synthese einiger 1,2‐Dihalogen‐norbornane
Authors: Krebs Ernst‐Peter , Keese Reinhart
Published: December 2004

Synthesis of some 1,2‐Dihalogenonorbornanes

The synthesis of 1,2exo‐Dibromo‐norbornane as well as the preparation of the configurational isomers of 2‐bromo‐1‐iodo‐ and 2‐chloro‐1‐iodo‐norbornane are described.
Synthese und Hydrolyse von 6endo‐substituierten p‐Toluolsulfonsäure‐[2endo‐norbornyl]estern. Norbornanreihe, 9. Mitteilung
Authors: Grob Cyril A. , Günther Bettina , Hanreich Reinhard
Published: December 2004

The Synthesis and Hydrolysis of 6endo‐Substituted 2endo‐Norbornyl p‐Toluenesulfonates

The hydrolysis products of the p‐toluenesulfonates of several hitherto unknown 6endo‐substituted 2endo‐norbornanols have been determined.
Arylierungen von cyclischen Guanidin‐Analogen mit α‐halogenierten Anthrachinonen: neue Anthrapyrimidine
Authors: Adam Jean‐Marie , Winkler Tammo , Rihs Grety
Published: December 2004

Arylation Reaction of Cyclic Guanidine‐Analogs with α‐Halo‐ anthraquinones: New Anthrapyrimidines

2‐Amino‐benzimidazole gives on Ullmann‐reaction with α‐halo‐athraquinones such as 1‐amino‐4‐bromoanthraquinone‐2‐sulfonic acid (la) the new benzimidazo‐anthrapyrimidine 2a, whereas 3‐amino‐ triazole gives under the same conditions two products: the 1,2,4‐triazoloanthrapyrimidine 7 and l‐amino‐4‐(3‐amino‐1,2,4‐ triazolyl)anthraquinone‐2‐sulfonic acid (8). The new structures were elucidated by 1H‐ and 13C‐NMR. and X‐ray analysis.
Consecutive Application of the α‐Alkynone Cyclization: Total Synthesis of (±)‐Δ9(12)‐Capnellene
Authors: Huguet Joan , Karpf Martin , Dreiding André S.
Published: December 2004

The synthesis of the (±)‐form of the marine sesquiterpene (–)‐Δ9(12)‐capnellene (1) by double application of the a‐alkynone cyclization is described. Starting with 2, 2, 5‐trim ethylcyclopentanone (2), the elaboration of the tricyclo [6.3.0.02,6]undecane C‐skeleton of 1 proceeded through the a‐alkynone 3, which was cyclized thermally to the bicyclo [3.3.0]octenone 4. For the anellation of the third five‐membered ring, 4 was transformed into the a‐alkynone 5 and the latter cyclized thermally to a mixture of the angular triquinenone 6 and the linear triquinenone 7. The last steps in the synthesis of (±)‐Δ9(12)‐capnellene (1) were then accomplished from 7 by known methods.
Synthesis of Unbranched 4‐Alkylbenzaldehydes
Authors: Osman Maged A.
Published: December 2004

The preparation of unbranched 4‐alkylbenzaldehydes free of positional and branched‐chain isomers by different methods is described. A one‐step preparation of the aldehydes is reported which involves the ‐direct hydrogenation of a Friedel Craft's complex in the presence of Pd/C catalyst.
A Further Synthetic Approach to the Adamantane Isomer 2, 5‐Trimethylenenorbornane (Tricyclo [5.3.0.03,9]decane, 4‐Homotwistbrendane)
Authors: Känel Hans‐Ruedi , Ganter Camille
Published: December 2004

A further synthetic approach to 2, 5‐trimethylenenorbornane (1; tricycle [5.3.0.03,9]decane, 4‐homotwistbrendane), a member of the «adamantaneland», is described starting from methyl 5‐oxo‐2endo‐norbornanecarboxylate (5). The required C2‐chain was introduced by a Wittig‐Horner reaction and the ring closure of the trimethylene bridge achieved by an acyloin condensation.
Effect of Doping and Solution Redox Relays on the Efficiency of Photocathodic Processes at the p‐InP/Water Interface
Authors: Geiger Thomas , Nottenberg Richard , Pélaprat Mary‐Lou , Grätzel Michael
Published: December 2004

Light‐induced interfacial electron transfer from two p‐InP electrodes differing in the amount of majority carrier doping to a number of electron relays (R) dissolved in aqueous solution was investigated. The material with the lower carrier density (0.71 × 1018 cm−3) exhibited much better wavelength response and quantum yield for electron transfer than the electrode doped with 2.3 × 1018 cm−3 charge carriers. Using cobalt (III) sepulcrate, Co (sep)3+, as an electron relay a polychromatic light to electrical energy conversion efficiency of 18% was obtained. The potential of this relay for use in a regenerative photoelectrochemical cell is briefly discussed.
The Existence of Helical Chirality in a Sterically Congested Naphtho [9]annulenone Preliminary Communication
Authors: Anastassiou Apostolos G. , Hasan Misbahul
Published: December 2004

The existence of the naphtho [9]annulenone 1 in two skeletally enantiomeric forms is demonstrated with the use of 1HNMR. spectroscopy in conjunction with a chiral «shift» reagent.
Alkylative amination of non‐enolizable aldehydes with alkyl (dialkyl‐amino)titanium derivatives Preliminary Communication
Authors: Seebach Dieter , Schiess Martin
Published: December 2004

The readily available tris (diethylamino)methyltitanium and related compounds (see 1 in Scheme 2) react with non‐enolizable aldehydes to give tertiary amines 2; these amines result from direct replacement of the carbonyl O‐atom by an alkyl and an amino group (Scheme 3). A tentative mechanism is proposed, according to which the amino group is transferred to the carbonyl C‐atom prior to the alkyl group (Scheme 4).
nucleophilic addition to C,C‐double bonds. VII. Study of proximity effects in olefinic alcohols and amines by photoelectron spectroscopy
Authors: Tombo Gerardo M. Ramos , Ammann Hans Jakob , Müller Klaus , Ganter Camille
Published: December 2004

The influence of steric compression on electronic structure in polycyclic olefinic alcohols and amines is studied by PE. spectroscopy.

The unsubstituted alcohol 2 and amine 7 show PE.‐spectroscopic properties that can be reconciled by postulating a predominance of intramolecularly H‐bonded species in the gas phase.

For the alkylated derivatives 5 and 9, in which H‐bonding is precluded, distinct, but only moderate lone‐pair double‐bond interactions are observed.
Zur Synthese sulfonierter Derivate von 2‐Fluoranilin
Authors: Courtin Alfred
Published: December 2004

Syntheses of Sulfonated Derivatives of 2‐Fluoroaniline

Synthesis of 4‐amino‐3‐fluorobenzenesulfonic acid (3) was achieved in two ways: reaction of 2‐fluoroaniline (1) with amidosulfonic acid and by first conventionally converting 4‐nitro‐3‐fluoroaniline (8) to 4‐nitro‐3‐fluorobenzenesulfonyl chloride (9) followed subsequently by hydrolysis to 3‐fluoro‐4‐nitrobenzenesulfonic acid (10) and reduction. Hydrogenolysis of 3 gave sulfanilic acid (7). Both, sulfonation of fluorobenzene (6) to 4‐fluorobenzenesulfonic acid (11) followed by nitration and sulfonation of 1‐fluoro‐2‐nitrobenzene (12) led to 4‐fluoro‐3‐nitrobenzenesulfonic acid (13). Reduction of 13 gave the isomeric 3‐amino‐4‐fluorobenzenesulfonic acid (4), which was also obtained both by sulfonation of 1 and by sulfonation of o‐fluoroacetanilide (14) followed by hydrolysis. Selective hydrogenolyses of 2‐amino‐5‐bromo‐3‐fluorobenzenesulfonic acid (15), prepared by reaction of 4‐bromo‐2‐fluoroaniline (16) with amidosulfonic acid, and of 4‐amino‐2‐bromo‐5‐fluorobenzenesulfonic acid (20), obtained by sulfonation of 5‐bromo‐2‐fluoroaniline (19) yielded the isomers 2‐amino‐3‐fluorobenzenesulfonic acid (5) and 3, respectively. The fourth isomer, 3‐amino‐2‐fluorobenzenesulfonic acid (2), was synthesized by sulfur dioxide treatment of the diazonium chloride derived from 2‐fluoro‐3‐nitroaniline (21) to 2‐fluoro‐3‐nitrobenzenesulfonyl chloride (22), followed by hydrolysis to 2‐fluoro‐3‐nitrobenzenesulfonic acid (23) and final Béchamp‐reduction.
Die Synthese von 2,3,4,5‐1H‐Tetrahydroimidazo[2,1‐b]chinazolin‐2,5‐dionen und analogen 2,3,4,5‐1H‐Tetrahydroimidazo[1,2‐a]thieno[2,3‐d] (bzw. [3,2‐d])‐pyrimidin‐2,5‐dionen
Authors: Kienzle Frank , Kaiser Ado , Minder Rudolf E.
Published: December 2004

The Synthesis of 2,3,4,5‐1H‐Tetrahydroimidazo[2,1‐b]quinazolin‐2,5‐diones and analogous 2,3,4,5‐1H‐Tetrahydroimidazo[1,2‐a]thieno[2,3‐d] (or [3,2‐d])‐pyrimidin‐2,5‐diones

The syntheses of various imidazo [2, 1‐b]quinazolinediones and their thiophene analogs are described.
(η‐Cyclopentadienyl)[1‐4‐η‐(5exo‐cyclopentadienyl‐1,3‐cyclopentadien)]cobalt(I)
Authors: Bönnemann Helmut , Radermacher Michael , Krüger Carl , Kraus Hans‐Jüger
Published: December 2004

Reaction of cobaltocene with cyclopentadiene and air results in the formation of the title compound; its structure has been elucidated by spectroscopic and X‐ray methods.
13C‐NMR.‐Substituenteninkremente der N3‐Gruppe in Azido‐1,4‐benzochinonen
Authors: Neidlein Richard , Kramer Walter , Leidholdt Rolf
Published: December 2004

13C‐NMR. Substituent Increments of the Azido‐group in 1,4‐Benzoquinones

The empirical substituent increments of the azido‐group in 1,4‐benzoquinones have been derived from the 13C‐NMR. chemical shifts of 2‐azido‐5‐chloro‐1,4‐benzoquinone. The validity of the obtained values was tested by comparison of the empirical and computed 13C‐NMR. chemical shifts of other azido‐chloro‐1,4‐benzoquinones.
Synthèse de spirohydantoines dérivées du diphényl‐2,4‐aza‐3‐bicyclo‐[3.3.1]nonane et du diphényl‐7,9‐aza‐8‐bicyclo[4.3.1]decane par réaction de Bucherer dans la N,N‐diméthylformamide: Influence de la température et cours stéréochimique. Communication préliminaire
Authors: Martínez Ernesto , del Campo Carmen , Trigo Gregorio G.
Published: December 2004

Synthesis of Spyrohydantoines Derivatives of 2,4‐Diphenyl‐3‐azabicyclo[3.3.1]nonane and 7,9‐Diphenyl‐8‐azabicyclo[4.3.1]decane via Bucherer Reaction in N,N‐Dimethylformamide: Influence of the Temperature and Stereochemical Path

The unreactives ketones related to 2,4‐diphenyl‐3‐azabicyclo [3.3.1]nonan‐9‐one to the Bucherer reaction in usuals conditions show excellent reactivity in DMF. as unique solvant. The stereochemical paths of these reactions and the synthetic utility of the temperature modification are described.
Photochromisme des spiropyrannes. Photodégradation d'aza‐, oxaza‐ et thiaza‐cyclopentane‐ et ‐cyclohexanespiropyrannes
Authors: Gaude Didier , Gautron René , Maguet Michel , Guglielmetti Robert
Published: December 2004

Photochromism of spiropyrans. Photodegradation of aza‐, oxaza‐, and thiaza‐cyclopentane‐ and ‐cyclohexanespiropyrans

Study of the photodegradation of saturated azaheterocyclic spiropyrans showed that electron‐donor substituents improve, as in the benzoheterocyclic series, the fatigue properties towards. UV. light. The introduction of oxygen or sulfur in the 5‐ or 6‐membered saturated azacycles or the substitution with an orthofused aromatic nucleus have practically no influence on the results of photodegradation. The indolinospiropyrans allow the greatest number of photochromic cycles before falling to half the initial absorbance on photolysis under accurate conditions.
Über die Dicyanierung der 1,4‐Diaminoanthrachinone und die Reaktivität der 1,4‐Diamino‐9,10‐dihydroanthracen‐2,3‐dicarbonitrile gegenüber nucleophilen Reagenzien 3. Mitteilung über Arylierungen und Heterocyclisierungen von Anthrachinonsystemen
Authors: Adam Jean‐Marie , Winkler Tammo
Published: December 2004

The Dicyanation of 1,4‐Diaminoanthraquinones and the Reactivity of 1,4‐Diamino‐9,10‐dioxo‐9,10‐dihydroanthracene‐2,3‐dicarbonitriles towards Nucleophilic Reagents

The reaction of 1‐amino‐9, 10‐dioxo‐4‐phenylamino‐9,10‐dihydroanthracene‐2‐sulfonic acid (1, RC6H5) with cyanide in water yields a mixture of 1‐amino‐9,10‐dioxo‐4‐phenylamino‐9,10‐dihydroanthracene‐2‐carbonitrile (3, R  C6H5) and 1‐amino‐4‐(phenylamino)anthraquinone (4, R  C6H5) under the usual reaction conditions (Scheme 1). In dimethylsulfoxide, however, a second cyano group is introduced, and 1‐amino‐9,10‐dioxo‐4‐phenylamino‐9,10‐dihydroanthracene‐2,3‐dicarbonitrile (7) is formed (Scheme 2). The cyano groups are very reactive towards nucleophiles. The cyano group in 2‐position can be substituted by hydroxide and aliphatic amines (Schemes 5 and 6). The cyano group in 3‐position can be eliminated by aliphatic amines and hydrazine (Scheme 7). Nucleophilic attack at the cyano C‐atom of the 2‐cyano group by suitable reagents leads to ring formation, yielding e.g. 2‐(Δ2‐1, 3‐oxazolin‐2‐yl)‐, 2‐(benz[d]imidazol‐2‐yl)‐ and 2‐(1H‐tetrazol‐5‐yl)anthraquinones (Schemes 8 and 10).
Das Carotinoidspektrum der Hagebutten von Rosa pomifera: Nachweis von (5Z)‐Neurosporin; Synthese von (3R, 15Z)‐Rubixanthin
Authors: Märki‐Fischer Edith , Marti Urs , Buchecker Richard , Eugster Conrad Hans
Published: December 2004

Carotenoids from Hips of Rosa pomifera: Discovery of (5Z)‐Neurosporene; Synthesis of (3R, 15Z)‐Rubixanthin

Extensive chromatographic separations of the mixture of carotenoids from ripe hips of R. pomifera have led to the identification of 43 individual compounds, namely (Scheme 2): (15 Z)‐phytoene (1), (15 Z)‐phytofluene (2), all‐(E)‐phytofluene (2a), ξ‐carotene (3), two mono‐(Z)‐ξ‐carotenes (3a and 3b), (6 R)‐ϵ, ψ‐carotene (4), a mono‐(Z)‐ϵ, ψ‐carotene (4a), β, ψ‐carotene (5), a mono‐(Z)‐β, ψ‐carotene (5a), neurosporene (6), (5 Z)‐neurosporene (6a), a mono‐(Z)‐neurosporene (6b), lycopene (7), five (Z)‐lycopenes (7a–7e), β, β‐carotene (8), two mono‐(Z)‐β, β‐carotenes (probably (9 Z)‐β, β‐carotene (8a) and (13 Z)‐β, β‐carotene (8b)), β‐cryptoxanthin (9), three (Z)‐β‐cryptoxanthins (9a–9c), rubixanthin (10), (5′ Z)‐rubixanthin (=gazaniaxanthin; 10a), (9′ Z)‐rubixanthin (10b), (13′ Z)‐ and (13 Z)‐rubixanthin (10c and 10d, resp.), (5′ Z, 13′ Z)‐ or (5′ Z, 13 Z)‐rubixanthin (10e), lutein (11), zeaxanthin (12), (13 Z)‐zeaxanthin (12b), a mono‐(Z)‐zeaxanthin (probably (9 Z)‐zeaxanthin (12a)), (8 R)‐mutatoxanthin (13), (8 S)‐mutatoxanthin (14), neoxanthin (15), (8′ R)‐neochrome (16), (8′ S)‐neochrome (17), a tetrahydroxycarotenoid (18?), a tetrahydroxy‐epoxy‐carotenoid (19?), and a trihydroxycarotenoid of unknown structure.

Rubixanthin (10) and (5′ Z)‐rubixanthin (10a) can easily be distinguished by HPLC. separation and CD. spectra at low temperature. The synthesis of (3 R, 15 Z)‐rubixanthin (29) is described.

The isolation of (5 Z)‐neurosporene (6a) supports the hypothesis that the ϵ‐end group arises by enzymatic cyclization of precursors having a (5 Z)‐ or (5′ Z)‐configuration.
Synthesis and X‐Ray Analysis of a Nickel Triphenyl‐Cyclopropenyl Complex. A mo‐interpretation of the geometry and bonding in the (C3H3)ML3‐type of complexes
Authors: Mealli Carlo , Midollini Stefano , Moneti Simonetta , Albright Thomas A.
Published: December 2004

The reaction of [(C3Ph3)Ni(PPh3)2]ClO4 with P(CH2CH2PPh2)3(pp3) and NaBPh4 yields the [(C3Ph3)Ni(pp3)]BPh4‐complex. After long exposure of the solution of this compound in acetone/butanol to the air a new derivative [(C3Ph3)‐Ni(pp2po)]BPh4· 0.5 C4H9OH, where pp2po is (Ph2PCH2CH2)2P(CH2 CH2POPh2), is obtained. Complete X‐ray analysis has been carried out for the latter complex: a=18.303 (5); b=29.445 (6), c=13.305 (5) Å, β=112.70 (9)°; space group monoclinic, P21/a, Z=4. Disorder problems were encountered in the refinement of the structure. The best R is 0.093. One of the arms of the parent pp3‐molecule, not coordinated to the metal, undergoes oxidation. The Ni‐atom, coordinated by the three remaining P‐atoms of the ligand, is also linked in a roughly η3‐mode to the cyclopropenium ligand. The geometry of the molecule is examined in detail. Extended HMO‐calculations were performed to interpret how the variation of PNiP angles affects the bonding between the NiP3‐ and C3H3‐fragments. The conclusion is that the overall energy of the complex may be lowered in spite of a weakening of the Ni‐cyclopropenium linkage. Extensions are made to other systems containing a linkage between a metal and a X3‐ring (X=P,As).
Synthesen des Analgetikums 2‐[1‐(m‐Methoxyphenyl)‐2‐cyclohexen‐1‐yl]‐N,N ‐dimethyl‐äthylamin
Authors: Bruderer Hans , Bernauer Karl
Published: December 2004

Syntheses of the Analgesic 2‐[1‐(m‐Methoxyphenyl)‐2‐cyclohexen‐1‐yl] ‐N,N‐dimethyl‐ethylamine

Three principal routes to 2‐[1‐(m‐methoxyphenyl)‐2‐cyclohexen‐1‐yl]‐ N,N‐dimethyl‐ethylamine (13), a compound with interesting analgesic properties, are described. In the first, derivatives of [1‐(m‐methoxyphenyl)‐2‐cyclohexen‐1‐yl]acetic acid (10) (alternatively the ethyl ester 29, the dimethylamide 32 or the nitrile 34) serve as crucial intermediates. All three can be synthesized from 2‐(m‐methoxyphenyl)cyclohexanone (1) by sequences comprising successively C‐alkylation (1→2,4,5; Scheme 1), reduction of the ketone carbonyl group (2→6;4→18;5→19; Scheme 1 and 2) and elimination (16→29; 18→32; 19→34; Scheme 2). The relative configuration of the cyclohexanols 16, 18, 19 and of a series of related compounds is established by chemical correlation with the lactone 30 the structure of which follows from 1H‐NMR. data (Scheme 2). The second route creates the intermediates 29 and 32 by ester‐ or amide‐enolate‐Claisen‐type‐rearrangement reactions starting from 3‐(m‐methoxyphenyl)‐2‐cyclohexen‐1‐ol (39; Scheme 3). Compounds 29, 32 and 34 are transformed into the target molecule 13 by standard reactions. A Hofmann elimination of the quaternary ammonium fluoride 50 (X=F), derived from the known cis‐perhydroindoline 48, is the essential step in the third approach to 13 (Scheme 4).
Polarographische Untersuchungen an symmetrischen Triazacarbocyaninen in Methanol
Authors: Hellrung Bruno
Published: December 2004

Polarographic Investigations on Symmetrical Triazacarbocyanine Dyes in Methanol

The reduction mechanism of eleven symmetrical triazacarbocyanine dyes with different heterocycles in methanol (containing lithium chloride or lithium acetate/acetic acid) has been investigated by means of polarography, cyclic oscillopolarography and coulometry.

The reduction occurs in a reversible to irreversible two electron transfer step, followed by an irreversible chemical step. Reduction potentials, transfer coefficients and specific currents have been measured and compared with properties measured in acetonitrile.

The effect of substituents X has been studied on the compounds 1‐ethyl‐2‐[3‐(1‐ethyl‐6‐X‐1,2‐dihydroquinolin‐2‐ylidene)‐1‐triazeno]‐6‐X‐quinolinium tetrafluoroborate 1f(X) and 3‐ethyl‐2‐[3‐(3‐ethyl‐5‐X‐Δ4‐1, 3‐thiazolin‐2‐ylidene)‐1‐triazeno]‐5‐X‐1, 3‐thiazolium tetrafluoroborate 1g(X), and ρ‐values of 0.20 and 0.40 V, respectively, have been found.
Synthesis of 2‐Oxo‐2H‐[1,2,4]oxadiazolo‐[2,3‐c]pyrimidine‐5‐carbamates
Authors: Hengartner Urs , Muller Jean‐Claude , Ramuz Henri
Published: December 2004

Thermal cyclization of the pyrimidine‐N‐oxide dicarbamate 2 gives a 95:5 mixture of the 2‐oxo‐2H‐[1,2,4]oxadiazolo[2,3‐a]‐ and [2,3‐c]pyrimidinecarbamates 3 and 4. An efficient procedure for the conversion of 3 to 4, and vice versa, is described.
Synthesis of (5R)‐ and (5S)‐5‐Methyl‐5, 6‐dihydrouridine Derivatives
Authors: Škarić Vinko , Matulić‐Adamić Jasenka
Published: December 2004

The hydrogenation of 2′, 3′‐O‐isopropylidene‐5‐methyluridine (1) in water over 5% Rh/Al2O3 gave (5 R)‐ and (5 S)‐5‐methyl‐5, 6‐dihydrouridine (2), separated as 5′‐O‐(p‐tolylsulfonyl)‐ (3) and 5′‐O‐benzoyl‐ (5) derivatives by preparative TLC. on silica gel and ether/hexane developments. The diastereoisomeric differentiation at the C(5) chiral centre depends upon the reaction media and the nature of the protecting group attached to the ribosyl moiety.

The synthesis of iodo derivatives (5 R)‐ and (5 S)‐4 is also described. The diastereoisomers 4 were converted into (5 R)‐ and (5 S)‐2′, 3′,‐O‐isopropylidene‐5‐methyl‐2, 5′‐anhydro‐5, 6‐dihydrouridine (7).
Structural Detail and Thermal Bond Relocation of a Sterically Strained Cyclononatetraene Preliminary Communication
Authors: Anastassiou Apostolos G. , Kasmai Hamid S. , Sabahi Mahmood
Published: December 2004

The X‐ray crystallographic molecular dimensions and thermal response of the 5, 13‐diphenyl‐cyclonoa [b]naphthalene 1a, are described.
Singlet Oxygen and Superoxide: Experimental Differentiation and Analysis
Authors: Maurette Marie‐Thérèse , Oliveros Esther , Infelta Pierre P. , Ramsteiner Klaus , Braun André M.
Published: December 2004

Superoxide produced by either pulse radiolysis or from KO2 undergoes no reaction with furfuryl alcohol competitive to the corresponding endo‐peroxide formation with singlet oxygen. Thus, furfuryl alcohol can be used as a specific chemical quencher of singlet oxygen.

Superoxide can be quantitatively analyzed by its electron transfer reaction with 1, 4‐benzoquinone.

The differentiation of the two activated species of oxygen has been realized in microemulsions. Singlet oxygen is known to penetrate the interfaces of surfactant aggregates and may be analyzed in the hydrophobic core by known methods. Charged surfaces on such aggregates, specially those formed by anionic surfactants, prevent the passage of superoxide and restrict its presence and the need for analysis to the bulk aqueous phase.

Hydrated electrons may penetrate the interface depending on the dose per pulse applied. 2, 5‐Di (t‐butyl)‐1, 4‐benzoquinone has been taken as an acceptor for electron transfer reactions within the hydrophobic core.
Optisch aktive C5‐Bausteine zur Synthese von natürlich vorkommenden Terpenen
Authors: Dumont Raymond , Pfander Hanspeter
Published: December 2004

Optically Active C5‐Synthons for the Synthesis of Naturally Occurring Terpenes

The optically active synthons (S)‐22, (R)‐23, (R)‐25 and (R)‐26 were prepared from L‐serine. Furthermore the tertiary alcohol 6 was synthesized from L‐serine (→(S)‐6) and D‐mannitol (→(R)‐6). These compounds are suitable for the synthesis of optically active natural products.
Nitrocyclopropyl‐Anion: A Triplet Ground State Molecule??
Authors: Wagner Hans‐Ulrich , Boche Gernot
Published: December 2004

STO‐3G calculations show that the nitrocyclopropyl anion prefers a triplet ground state with a tetrahedral C(α)‐atom and a perpendicular orientation of the three‐membered ring and the NO2‐group, 1–90° (Table 1). This unusual result is in agreement with recent experimental findings of Kai et al. (Helv. Chim. Acta 65, 137 (1982)). Other NO2‐anions as well as all CHO‐, COOH‐ and CN‐substituted anions 2–12, have singlet ground states 2–0°–12–0° (Table 1), in agreement with copious experimental data (Wagner & Boche, Z. Naturforsch. 37b, 1339 (1982)).
The Carbon Zip Reaction: A Method for Expanding Carbocycles
Authors: Nakashita Yoshihiko , Hesse Manfred
Published: December 2004

A general method for enlargement of carbocyclic rings by the so called zip reaction is given. The Michael adducts of 2‐nitrocycloalkanones with 3‐oxo‐4‐pentenoates in the presence of tetrabutylammonium fluoride give in high yield compounds with the ring enlarged by four C‐atoms. By this method 7‐, 8‐, and 12‐membered cycloalkanones were converted respectively to 11‐, 12‐, and 16‐membered functionalized carbocycles (see Scheme 2 and 3).
Absolute Konfiguration von Loroxanthin (=(3R, 3′R, 6′R)‐β, ϵ‐Carotin‐3, 19, 3′‐triol)
Authors: Märki‐Fischer Edith , Bütikofer Pierre‐André , Buchecker Richard , Eugster Conrad Hans
Published: December 2004

Absolute Configuration of Loroxanthin (=(3R, 3′R, 6′R)‐β, ϵ‐Carotene‐3, 19, 3′‐triol)

‘Loroxanthin’, isolated from Chlorella vulgaris, was separated by HPLC. methods in two major isomers, a mono‐cis‐loroxanthin and the all‐trans‐form. Solutions of the pure isomers easily set up again a mixture of the cis/trans‐isomers. Extensive 1H‐NMR. spectral measurements at 400 MHz allowed to establish the 3′, 6′‐trans‐configuration at the ϵ‐end group in both isomers and the (9E)‐configuration in the mono‐cis‐isomer. The absolute configurations at C(3) and C(6′) were deduced from CD. correlations with synthetic (9Z, 3R, 6′R)‐β, ϵ‐carotene‐3, 19‐diol (5) and (9E, 3R, 6′R)‐β, ϵ‐carotene‐3, 19‐diol (6), respectively. Thus, all‐trans‐loroxanthin (3) is (9Z, 3R, 3′R, 6′R)‐β, ϵ‐carotene‐3, 19, 3′‐triol and its predominant mono‐cis‐isomer is (9E, 3R, 3′R, 6′R)‐β, ϵ‐carotene‐3, 19, 3′‐triol (4). Cooccurrence in the same organism and identical chirality at all centers suggest that loroxanthin is biosynthesized from lutein (2).
Synthèse de composés cyclopentaniques chiraux, di, tri et tétrasubstitués. Application à la synthèse de dérivés Oxa‐13‐prostanoïques
Authors: Barrière Jean‐Claude , Cléophax Jeanine , Géro Stephan D. , Vuilhorgne Marc
Published: December 2004

The cyclopentenecarbaldehyde 1a, acetals 2a, 2b and the cyclopentenone 2c have been transformed through regio and stereocontrolled reactions into a variety of enantiomerically pure substituted cyclopentanes. Using appropriately selected Wittig reagents, aldehyde 1a furnished the condensation products 3, 4, 5. Michael addition of diethyl malonate on the α,β‐unsaturated aldehyde 1a under phasetransfer conditions led efficiently to 7. Reduction of the cyclopentenone 2c gave 21 in high yield. The cyclopentenes 2a, 2b and 23, submitted to hydroboration‐oxidation furnished the cyclopentanols 10, 13 and 24, respectively, in 30, 70 and 50% yields, reflecting the substitution pattern of the starting alkenes. The salient feature of these reactions is the stereospecificity due to the chiral centre of the molecules 1a, 2a, 2b and 2c, leading to compounds with two, three and four asymmetric centres. The straightforward synthesis of 11α‐hydroxy‐13‐oxaprostanoic acid 20 is described and an approach towards the preparation of 9α, 11α‐dihydroxy‐13‐oxaprostanoic acid 34 is also presented. The structure of these products has been determined by 1H‐ and 13C‐NMR spectroscopy.
The Radical Anions of Some Benzo‐Derivatives of Dehydrocyclooctatetraenes
Authors: Gerson Fabian , Heckendorn René , Wong Henry N. C.
Published: December 2004

The radical anions of 5,6‐didehydrobenzocyclooctene (3), 5,6,9,10‐tetradehydrobenzocyclooctene (4) and 1,4,7,10‐tetramethyl‐5,6‐didehydrodibenzo[a, e]‐cyclooctene (6) were prepared in situ from dibromo‐precursors and have been characterized by ESR and ENDOR spectroscopy.
The Photochemical Behaviour of 5,5‐Dimethyl‐2(5H)‐furanone
Authors: Anklam Elke , Margaretha Paul
Published: December 2004

The photochemical behaviour of the title compound 2c was investigated in various solvents. In benzene and t‐butanol photodimerization affords the cis‐anti‐cis HH‐ and HT‐dimers (H = head, T = tail). In acetonitrile, cyclohexane and 2‐propanol, photoreduction competes with photodimerization. The photoreduction products are hydrodimers, solvent adducts and the saturated lactone (the 2H‐reduction product). In acetonitrile and cyclohexane H‐abstraction by the β‐C‐atom of the CC bond is the predominant reduction process. In 2‐propanol, solvent adducts to the α‐ and β‐C‐atoms are formed in equal amounts. In xanthone‐sensitized irradiations the ratio of HH‐ to HT‐dimer is the same as on direct irradiation and the relative rates of conversion of 2c to products in different solvents are also similar under both conditions.
Electronic Absorption Spectra of Planar, Conjugated Biradicals in the Lowest Triplet State
Authors: Gisin Markus , Wirz Jakob
Published: December 2004

The semiempirical PPP‐SCF‐SCI method has been adapted to even‐electron, open‐shell π‐systems by performing the SCF calculation on the lowest triplet configuration and choosing a limited set of single electronic excitations from the latter for configuration interaction. The basic approximations and parameters of the standard PPP model were retained. The results were compared with experimental triplet‐triplet absorption spectra of aromatic hydrocarbons and with more elaborate calculations available for selected systems. The reliability of the model was found to be comparable to its well‐known performance in predicting the absorption spectra of closed‐shell π‐systems and of conjugated radicals. Triplet‐state absorption spectra for various planar, conjugated biradicals were calculated and, where possible, compared with experimental data.
The Distortion of Electrically Conducting, Thermodynamically Stable Microphases by an Electric Field
Authors: Eicke Hans‐Friedrich
Published: December 2004

O'Konski's considerations regarding the distortion of spherical droplets by electric fields in binary two‐phase systems has been extended to three‐component water/surfactant/oil systems with so‐called ultra‐low interfacial tensions, i.e. spherically aqueous microphases. It is shown that the deformation is almost negligible for fields up to about 5 105 Vm−1 such as those applied in electro‐optical Kerr‐effect measurements with microemulsions if only perturbations of the mean orientation of the surfactants in the interface are considered.
Zur Stabilität der Metallkomplexe von Methantriessigsäure und cis, cis‐1,3,5‐Cyclohexantricarbonsäure
Authors: Wu Yi‐He , Kaden Thomas A.
Published: December 2004

The stabilities of the Mn2+‐, Co2+‐, Ni2+‐, Cu2+‐ and Zn2+‐complexes with 2‐(carboxymethyl)glutaric acid (2) and cis,cis‐1,3,5‐cyclohexanetricarboxylic acid (3) were measured potentiometrically at 25° and I = 0.5 (KNO3). Beside the complexes ML− protonated species MLH and MLH are also formed. Their stability constants are given in Table 1. A comparison between the stabilities of 2 or 3 and those of acetate, as a model for a monocarboxylate, or succinate and glutarate, as examples for dicarboxylates, indicates that in all species only one carboxylate is strongly bound whereas the second and third ones are probably not.

The observation that Δlog K1 = log K − log K as well as Δlog K2 = log K − log K are practically constants with values of 0.34 ± 0.05 and 0.49 ± 0.07, respectively, for both ligands and the five metal ions studied is also in line with the proposed monodentate structures of the complexes ML−, MLH and MLH.