bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis, Isolation, and Full Spectroscopic Characterization of Eleven (Z)‐Isomers of (3R,3′R)‐Zeaxanthin
Authors: Englert Gerhard , Noack Klaus , Broger Emil A. , Glinz Ernst , Vecchi Max , Zell Reinhard 
Published: December 2004

AbstractDevelopmental efforts to improve the yield of the chemical synthesis of (3R,3′R)‐zeaxanthin resulted in the isolation, partly by chromatography from reaction mixtures, and full spectroscopic characterization by 1H‐NMR, UV/VIS, and CD spectrosocpy of eleven (Z/E)‐isomers of zeaxanthin: (7Z)‐, (9Z), (13Z)‐, (15Z)‐, (7Z,7′Z)‐, (9Z,9′Z)‐ (7Z,9Z,7Z)‐, (7Z,11Z,7′Z)‐, (9Z,13Z,9′Z)‐, (7Z,9Z,7′Z,9′Z)‐, and (7Z,9Z,11Z,7′Z,9′Z)‐zeaxanthin. Five of these isomers were obtained by specific synthesis, namely the (7Z)‐, (7Z,7′Z)‐, (9Z,9′Z)‐, (7Z,9Z,7′Z)‐, and (7Z,9Z,7′Z‐9Z)‐isomers.
3′‐Substituted and 2′,3′‐Unsaturated 7‐Deazaguanine 2′,3′‐Dideoxynucleosides: Syntheses and Inhibition of HIV‐1 Reverse Transcriptase
Authors: Seela Frank , Muth Heinz‐Peter 
Published: December 2004

AbstractThe syntheses of 2′,3′‐dideoxy‐2′,3′‐didehydro‐β‐D‐ribofuranoside 1 and 2′,3′‐dideoxy‐3′‐fluoro‐β‐D‐ribo‐furanoside 5 of 7‐deazaguanine as well as 7‐deaza‐2′‐deoxyxyloguanosine (3) are described. The corresponding 2,4‐diamino compounds 2 and 4 were also prepared. Thus, silytation of 2‐amino‐4‐chloro‐7‐(2‐deoxy‐β‐D‐erythro‐pentofuranosyl)‐7H‐pyrrolo[2,3‐d]pyrimidine (6) afforded 7, which gave the oxo‐nucleoside 13 after oxidation with CrO3. NaBH4 reduction yielded 14 which, upon deprotection (Bu4NF) and nucieophific displacement, afforded 3 and 4. On the other hand, the N2‐formyl derivative of 7 was mesylated (→ 10), treated with Bu4NF, and deprotected with NH3 yielding the 2′,3′‐dideoxy‐2′,3′‐didehydro‐nucleoside 12, Nucleophilic displacement reactions on 12 yielded 1 and 2. The fluoro‐nucleoside 5 was obtained from 14 after methoxytritylation of the NH2 group (→ 16), fluorination with DAST (→ 17), and treatment with 2M NaOH. The 5′‐triphosphates of 5 and other pyrrolo[2,3‐d]pyrimidine 2′,3′‐dideoxy‐3′‐fluoro‐nucleosides were found to be highly active inhibitors of HIV‐1. reverse transcriptase, similar to those of 1 and 2.
IR, Multinuclear‐NMR, and Structural Studies on [WH(CO)2(NO)(PR3)2]: cis‐Influence of Phosphorus Ligands on Hydride Character
Authors: Van Der Zeijden Adolphus A. H. , Sontag Christoph , William Bosch H. , Shklover Valery , Berke Heinz , Nanz Daniel , Philipsborn Wolfgang Von 
Published: December 2004

AbstractA thorough IR and 1H‐, 13C‐, 31P‐, 183W‐NMR spectroscopic, and X‐ray structural study was carried out on complexes of the type trans, trans‐[WH(CO)2(NO)(PR3)2], (R = Et, Me, Ph, i‐PrO, MeO, and PhO). Linear correlations could be found between Tolman's parameter X and v(CO), v(WH), v(NO), δ(13C) (CO), as well as 1n(k), k being the H/D exchange rate constant for the hydride in CD3OD. The 1J(183W,31P), 2J(31P,1H), and 2J(31P,13C) as well as the 1J(183W,1H) values are related to the electronegativity of the R groups on the phosphorus ligands. This is also indicated by EHT calculations of s‐orbital populations of appropiate W model complexes. The X‐ray structures of [WH(CO)2(NO)(PR3)2] (R = Me, Ph, and MeO) were determined. Minor differences were observed in the WP bond lenghts and in the PWP and CWC angles. No obvious relationship between X‐ray data and spectroscopic parameters could be found. All three structures reveal a bending of both the CO and PR3 ligands towards the hydride atom. The total octahedral distortion is remarkably constant (25.6, 29.4, and 27.0° tilt, respectively), although the ligands individually are very different. This is attributed to redistribution of π‐electron density between CO and PR3 groups toward the central W‐atom in the three complexes.
Einelektronen‐Redox‐Reaktionen von Octamethyl[4]radialen: Nachweis der Alternanz geradzahliger Radialene
Authors: Bock Hans , Rohn Günther 
Published: December 2004

One‐Electron Redox Reactions of Octamethyl[4]radialene: Proof of the Alternancy of Even‐Membered RadialenesThe photoelectron spectrum of octamethyl[4]radialene ( = tetrakis(dimethylmethylidene)cyclobutane) yields the rather low first vertical ionization of only 7.30 eV and, therefore, the molecule can be oxidized by AlCl3/CH2Cl2 to its radical cation. The ESR and ENDOR signal patterns recorded are almost identical with those of the radical anion, generated in a [2.2.2]cryptand THF solution by reduction at a potassium metal mirror. Their near congruency is in accord with the alternant π molecular properties of even‐membered radialenes as predicted by HMO theory, and larger changes of the D2d structure of C8(CH3)8 during the redox reactions are presumably hindered by the steric overcrowding in persubstituted [4]radialenes.
Alternative Strategies for the Fmoc Solid‐Phase Synthesis of O4‐Phospho‐L‐tyrosine‐Containing Peptides
Authors: Kitas Eric A. , Knorr Reinhard , Trzeciak Arnold , Bannwarth Willi 
Published: December 2004

AbstractA number of biologically relevant O4‐phospho‐L‐tyrosine‐containing peptides have been synthesized by either the global phosphorylation of the side‐chain‐unprotected L‐tyrosine moiety in presynthesized resin‐bound peptides or alternatively by the incorporation of suitably protected O4‐phospho‐L‐tyrosine building blocks in the continuous‐flow method of Fmoc solid‐phase peptide synthesis. Different phosphate‐protecting groups have been applied.
Stereoselektive Synthese von Pyrrolizidin‐Alkaloiden aus Nitroalkanonen
Authors: Janowitz Agnes , Vavrecka Mojmir , Hesse Manfred 
Published: December 2004

Stereoselective Synthesis von Pyrrolizidin Alkaloids from NitroalkanonesReduction of 5‐nitropentadecane‐2,8‐dione (11), synthesized by a Michael reaction from nitromethane, methyl vinyl ketone, and dec‐1‐en‐3‐one, gave, depending on the conditions, two epimeric 3‐heptyl‐2,3,5,6,7,7a‐hexahydro‐5‐methyl‐1H‐pyrrolizines as the main products: Catalytic hydrogenation (Pd/C) afforded the expected 7aα‐hydro epimer 1b with cis‐orieted H‐atoms at C(3), C(5), and C(7a). NaBH3CN/NH4OAc reduction of the nitrodione 11 yielded all four diastereoisomers with the 7aβ‐hydro epimer 1a as the predominant component; 1a is a pheromone of the cryptic thief ant Solenopsis sp. The N‐atom of the pyrrolizidine ring stems from NH4OAc exclusively as shown by reduction of 11 with NaBH3CN/(15N)H4OAc.
Synthesis of Aristotelia‐type alkaloids. Part IX. Synthesis of (±)‐alloaristoteline
Authors: Güller Rolf , Borschberg Hans‐Jürg 
Published: December 2004

AbstractThe probably most straightforward plan to synthesize the indole alkaloid alloaristoteline (5) failed, because– in marked contrast to the regular Aristotelia series‐electrophilic reagents attack with preference C(3) of the indole moiety in the key intermediate allohobartine ((−)‐12), instead of C(18). The only product that could be isolated when (−)‐12 was treated with mineral acid was isomer (+)‐15 of 5 (Scheme 2). As a consequence, the crucial electrophilic site at C(17) was created by taking recourse to the preparation of the stabilized allylic cation VI. Gratifyingly, this alleged intermediate, obtained from precursor (±)‐18, cyclized smoothly to protected (±)‐18,19‐didehydroalloaristoteline (±)‐17, which was transformed in two high‐yield steps into the racemic form of the target molecule 5 (Scheme 4). This successful alternative provides unambiguous evidence that the recently revised structure of 5 is indeed correct.
Dependence of the Regioselectivity of Photo‐oxidative Ring Opening of the Chlorophyll Macrocycle on the Complexed Metal Ion
Authors: Iturraspe José , Gossauer Albert 
Published: December 2004

AbstractOn irradiation with visible light in the presence of air, the zinc complex 1b of pyropheophorbide‐a methyl ester (1a) is photo‐oxidized at the C(20) methine bridge yielding the corresponding 19‐formyl‐21H‐bilin‐1(23H)‐one derivative 2. Surprisingly, the cadmium complex Ic is cleaved, under the same conditions, at the C(5) methine bridge affording the same type of bilinone which has been recently characterized as an early product of chlorophyll catabolism in plants.
Metal π‐complexes of benzene derivatives. Part. 38. Pentaphenyltriphosphane(5) as a chelating η12‐ligand. Unusual formation of an interannular –(PPh)3–bridge at bis(benzene)chromium
Authors: Elschenbroich Christoph , Sebbach Jochen , Metz Bernhard 
Published: December 2004

Abstract[(l‐6):(1′‐6′)‐η‐Pentaphenyltriphosphane(5)]chromium (8), which is formed from bis(lithio‐η6‐benzene)‐chromium and dichlorophenylphosphane, and which is prepared more rationally from bis(chloro‐η6‐benzene)‐chromium and K2P3Ph3, is the first sandwich complex featuring an interannular oligophosphane bridge –(PPh)n‐, n ≥ 2; 31P{1H}‐ and 1H‐NMR spectra suggest that the stereoisomer 8‐meso1 is formed exclusively and that the –(PPh)3‐ link in this triphospha[3]chromocyclophane is non‐fluxional in the range 193 < T < 348 K.
A Convenient Synthesis of Vinyl Sulfides
Authors: Katritzky Alan R. , Afridi Amir S. , Kuzmierkiewicz Wojciech 
Published: December 2004

Abstracttert‐Alkyl sulfides, with an α‐(1H‐benzotriazol‐1‐yl) group 6 and 13, are readily prepared from N‐[(aryl‐thio)methyl]‐1H‐benzotriazoles 3 and N‐(11), respectively, by reaction with BuLi and then with the appropriate electrophile. The tert‐alkyl sulfides 6 and 13 are smoothly converted by BF3. OEt2 into vinyl sulfides 5, 7 or 12, respectively, in satisfactory yields.
Isomerization of N‐[α‐(Alkylthio)alkyl]‐ and N‐[α‐(Arylthio)alkyl]benzotriazoles
Authors: Katritzky Alan R. , Kuzmierkiewic Wojciech , Perumal Subbu 
Published: December 2004

AbstractThe thermal isomerizations of N‐[α‐(alkylthio)alkyl]‐ and N‐[α‐(arylthio)alkyl]benzotriazoles have been investigated under N2 atmospheres (i) in toluene, xylene, MeOH, or EtOH, in the presence of acid catalysts and (ii) in the absence of solvent. The sulfide isomerization rates depend on the number of H‐atoms carried by the C‐atom attached to the N‐atom of the benzotriazole: tertiary (no hydrogen) > secondary (1 hydrogen) > primary (2 hydrogens). The results support an isomenzation mechanism involving a heterolytic NC bond cleavage with formation of sulfonium/carbonium and benzotriazolate ions.
Structure Determination of New Iridals from Iris pallida and Iris foetidissima
Authors: Littek Andrè , Marner Franz‐Josef 
Published: December 2004

AbstractThe four novel iridals 8–10 and 18 were isolated from rhizome extracts of Iris pallida and Iris foetidissima, and their structures were established by spectroscopic methods and oxidative degradation. The compounds 8–10 bearing a conjugated triene moiety are extremely labile and decompose rapidly. Thus, the monocyclic triene 8 was only isolated after its conversion to a Diels‐Alder adduct with 4‐phenyl‐3H‐1,2,4‐triazole‐3,5(4H)‐dione (14), The tricyclic iridal 18 is a hitherto unknown precursor of α‐irone. The possible biogenesis of these unusual triterpenoids is discussed.
Synthesis of a Glucose‐Derived Tetrazole as a New β‐Glucosidase Inhibitor. A New Synthesis of 1‐Deoxynojirimycin
Authors: Ermert Philipp , Vasella Andrea 
Published: December 2004

AbstractThe tetrazole 1 is a new β‐glucosidase inhibitor (IC50=8·10−5 M, Emulsin), obtained (92%) by deprotection of 22, the product of an intramolecular cycloaddition of the azidonitrile 20. This azidonitrile was formed as an intermediate by treating the L‐ido‐bromide 14 or the L‐ido‐tosylate 19 with NaN3 at 110–120°. It was isolated in a separate experiment. The yield of 22 from 19 reached 70%; 21 was formed as by‐product (10%). The bromide 14 (42%) and the iodide 15 (30–35%) were obtained from the nitrile 13, together with the 2,5‐anhydro‐L‐idononitrile 16, which was formed in ca. 35–45%. The tosylate 19 was obtained from 18 (97%). To obtain 18, the nitrile 13 was oxidized according to Swern (→17, 92%) and then reduced (NaBH4, CeCl3), leading to 18and 13 (92%, 18/13 93:7). Reduction of the tetrahydropyridotetrazole 22 with LiAlH4 afforded 83 % of the piperidine 23, which was deprotected to (+)‐1‐deoxynojirimycin hydroacetate (2·AcOH, 86%) and further converted into the corresponding hydrochloride and into the free base 2.
Radical Anions of Cyclic Azoalkanes: An ESR, ENDOR, and TRIPLE‐Resonance Study
Authors: Ess Caspar H. , Gerson Fabian , Adam Waldemar 
Published: December 2004

AbstractRadical anions often monocyclic and bicyclic azoalkanes containing the azo group in (Z)‐conformation, have been fully characterized by their hyperfine data with the use of ESR, ENDOR, and general‐TRIPLE‐resonance spectroscopy. These azoalkanes are represented by 3,3,5,5‐tetramethyl‐1‐pyrazoline (1), 2,3‐diaza‐bicyclo[2.2.1]hept‐2‐ene (4), and 2,3‐diazabicyclo[2.2.2]oct‐2‐ene (9), as well as by their derivatives 2,3, 5–8, and 10. For all radical anions 1″–10″, the 14N‐coupling constant, aN, is in the range of +0. 83 to +0. 97 mT; this finding indicates that the spin population is essentially restricted to the π system of the azo group. The 14N‐hyperfine anisotropy largely affects the width of ESR lines, particularly at low temperatures. Substantial coupling constants of 7Li‐, 23Na‐, 39K‐, and 133Cs‐nuclei point to a close association of the radical anions with their alkali‐metal counterions. With the exception of 39K, these nuclei give rise to readily observable ENDOR signals which appear along with those stemming from protons. The prominent hyperfine features of 1″–10″ are discussed.
Photochemical Reactions. 153th communication. Photochemistry of acylsilanes: Photolyses and thermolyses of α,β‐epoxy silyl ketones
Authors: Scheller Markus E. , Frei Bruno 
Published: December 2004

AbstractThe photolyses and thermolyses of the α,β‐epoxy silyl ketones 5 and 6 are described. On n,π*‐excitation, the silyl ketones 5 and 6 were transformed to the ketone 7 and the ketene 8 in quantitative yield. The formation of 8 may be explained by initial cleavage of the C(α)O bond and subsequent C(1)→C(2) migration of the (t‐Bu)Me2Si group. In contrast to the acylsilanes 5 and 6, the photolyses of the analogous methyl ketones 11 and 12 gave a very complex mixture of products. On thermolysis, 5 and 6 yielded the ketone 7 and the acetylenic compound 9, which were probably formed via a siloxycarbene intermediate. In addition, the 1,3‐dioxle 10 was formed via an initial C(α)C(β) bond cleavage leading to the ylide g and subsequent intramolecular addition of the carbonyl group. The analogous 1,3‐dioxole 13 was obtained on pyrolysis of the methyl ketones 11 and 12.
Synthesis of Enantiomeric Pure E‐Nor‐15‐azayohimbines
Authors: Valls Nativitat , Bonjoch Josep , Del Alamo Carlos , Bosch Joan 
Published: December 2004

AbstractA stereodivergent synthesis of enantiomerically pure E‐nor‐15‐azayohimbines via condensation of tryptamine with derivatives of pyroglutamate 4 is reported. When the Pictet‐Spengler reaction was induced in refluxing aqueous AcOH a nearly equimolar ratio of lactams 7 and 8 was obtained, whereas under kinetic control (TFA, room temperature) the trans‐derivative 8 was the major product. In contrast, cyclization of amido acetal 12 with TsOH gave the cis‐derivative 7 as preponderant component.
Einelektronen‐Redox‐Reaktionen von Octaphenyl[4]radialen: Erzeugung und ESR/ENDOR‐Charakterisierung seines Radikal‐Anions und Radikal‐Kations
Authors: Bock Hans , Rohn Günther 
Published: December 2004

One‐Electron Redox Reactions of Octaphenyl[4]radialene: Generation and ESR/ENDOR Characterisation of Its Radical Anion and Radical CationThe cyclovoltammograms of octaphenyl[4]radialene in DMF or THF at room temperature disclose each two quasireversible reduction and oxidation potentials at −1.4 V/−1.7 V and +0.7 V/+0.9 V. Accordingly, both the radical anion and the radical cation can be generated: Ph8C by K metal mirror reduction of a [2.2.2]cryptand containing THF solution, and Ph8C by TI3⊕(⊖OOCCF3)3 oxidation in H2CCl2. Their ESR/ENDOR and General Triple spectra differ considerably in the number of resolved 1H couplings (M·⊖: 5 and M·⊕: 3) as well as in their spectral widths (M·⊖: a1H 0.090 to 0.017 mT; M·⊕: a1H 0.066 to 0.023 mT) suggesting different changes in the D2d structure of the neutral molecule on electron uptake or extrusion.
Investigations Concerning an Unexpected Reaction between the Dimsyl Anion ( = (Methylsulfinyl)methanide) and a γ,δ‐Epoxy‐ketone
Authors: Beerli René , Borschberg Hans‐Jürg 
Published: December 2004

AbstractThe reaction of 2,2‐dimethyl‐5‐(1,2‐epoxypropyl)cyclohexanone (7) with t‐BuOK in DMSO furnished a small amount of 5‐(1‐hydroxyprop‐2‐enyl)‐2,2‐dimethylcyclohexanone (12) and the 4 unexpected products 13–16 which contain one to three additional C‐atoms (Scheme 2). The relative configuration of the major product 1‐(4′,4′‐dimethyl‐2′,3′‐dimethylidenecyclohexyl)propane‐1,2‐diol (15) was shown to be 1RS, 2RS,1′SR via NOE measurements performed on a derivative thereof. A crossover experiment in DMSO/[13C2]DMSO 1:1 as solvent showed that the two additional C‐atoms of this product originate from a single molecule of DMSO (Scheme 5). A tentative mechanistic scheme, consistent with all experimental observations, is proposed which involves a [2,3]‐sigmatropic rearrangement of an (allylsulfinyl)methanide to a sulfenic acid as one of the key steps (V → 24, Scheme 8). We corroborated part of this hypothetic scheme by taking recourse to a model compound (7‐(methylsulfinyl)‐p‐mentha‐1,8‐diene (32/33), readily prepared in two steps from perilla alcohol (30)), which reacted as predicted by the proposed mechanism (Schemes 9 and 10).
Opening of the Macrocyclic Ring in 5,10:8,9‐Disecosteroids ( = Steroklastanes)
Authors: Lorenc Ljubinka , Bondarenko‐Gheorghiu Lidija , Pavlović Vladimir , Fuhrer Hermann , Kalvoda Jaroslav , Mihailović Mihailo Lj. 
Published: December 2004

AbstractCatalytic hydrogenation of the Δ3‐unsaturated (9R,10 R)‐ and (9S,10 S)‐epoxyenol lactones 3a, b., and 4a, b., respectively, affords, in addition to the expected saturated epoxylactones 5a, b and 7a, b, also open‐chain products, i.e. the diastereoisomeric (9R,10R)‐ and (9S,10S)‐9,10‐expoxy‐8‐oxo‐4,5‐secosteroklastan‐5‐oic acids 6a, b. and 8a, b. Alkaline hydrolysis of the lactone ring of compounds 5 and 7 and subsequent acetylation of the corresponding hydroxy derivatives give as the major products the open‐chain, diasteroisomeric (9R,10R)‐ and (9S,10S)‐4‐acetoxy‐9,10‐epoxy‐methyl esters 9a, b and 11a, b, respectively, and, but only in the androstane series, the tetrahydropyran derivatives 10a and 12a, as the minor components.
Epimeric Isopavine N‐Oxides from Roemeria refracta
Authors: Gözler Belkis , Ali Önür Mustafa , Bilir Serap , Hesse Manfred 
Published: December 2004

AbstractRoemeria refracta DC. (Papaveraceae) of Turkish origin yielded two novel epimeric N‐oxides, (−)‐(5R, 11S,14R)‐reframidine N‐oxide ( = (−)‐(5R, 11S,14R)‐11,12‐dihydro‐14‐methyl‐11,5‐(iminomethano)‐5H ‐cyclohepta[1, 2‐f: 4, 5‐f′]bis[1,3]benzodioxole 14‐oxide; 1) and (−)‐(5R, 11S, 14S)‐reframidine N‐oxide ( = (−)‐(5R, 11S, 14S)‐11, 12‐dihydro‐14‐methyl‐11, 5‐(iminomethano)‐5H‐cyclohepta[1, 2‐f:4, 5‐f′]bis[1, 3]benzodioxole 14‐oxide; 2). The isolated (−)‐roelactamine ( = (−)‐11, 12‐dihydro‐14‐methyl‐11, 5‐(iminomethano)‐5H‐cyclohepta[1, 2‐f:4, 5‐f′]bis[1, 3]benzodioxol‐15‐one, 4) is the first natural isopavinoid incorporating a lactam group. The epimeric (−)‐15‐(2‐oxopropyl)reframidines ( = (−)‐1‐[11, 12‐dihydro‐14‐methyl‐11, 5‐(iminomethano)‐5H‐cyclohepta[1, 2‐f:4, 5‐f′]bis[1, 3]benzodioxol‐15‐y1]propan‐2‐ones; 5/6) and the epimeric (−)‐ethyl (reframidin‐15‐yl)acetates ( = (−)‐ethyl [11, 12‐dihydro‐14‐methyl‐11, 5‐(iminomethano)‐5H‐cyclohepta[1, 2‐f:4, 5‐f′]bis[1, 3]benzodioxol‐15‐y1]acetates; 7/8) are probably artifacts. (±)‐Coclaurine (9), (±)‐N‐methylcoclaurine (10), (−)‐roemeridine (11), and N‐feruloyltyramine (12) are also isolated from R. refracta together with the previously reported bases. Specific 13C‐NMR assignments are reported for the first time for the isopavines.
Quantum Yields of Singlet‐Oxygen Production by Some Natural Quinoid Fungal Metabolites and Derivatives
Authors: Aminian‐Saghafi Taraneh , Nasini Gianluca , Caronna Tullio , Braun André M. , Oliveros Esther 
Published: December 2004

AbstractPerylene quinone compounds of natural and syntheitc origin have been investigated for their quantum efficiency of singlet‐oxygen production (ΦΔ). The results may be interpreted by a qualitative relation between ΦΔ and the planarity of the sensitizer molecules, highest values (0.8–0.9) being observed where planarity is favoring tautomeric structures. On the other hand, derivatives exhibiting non‐planar quinoid structures show lower ΦΔ, and methylated derivatives react photochemically.
Cuprous Complexes and Dioxygen. Part 12.. Rate law and mechanism of the copper‐catalyzed oxidation of ascorbic acid in aqueous acetonitrile
Authors: Mi Li , Zuberbühler Andreas D. 
Published: December 2004

AbstractThe copper‐catalyzed oxidation of ascorbic acid (AscH2) has been studied with a Clark electrode in aqueous MeCN. CuI or CuII may be equally used as the source of metal ion, without influence on the rate law. At sufficiently high [MeCN], the rate of the overall reaction is essentially given by the rate of CuI autoxidation: the reaction is of first order with respect to [Cu] and [O2] and shows an inverse‐square dependence on [MeCN] as observed for the autoxidation of Cu. The pH dependence is complicated by the combination of the intrinsic pH effect on autoxidation with an additional term in the rate law which is directly proportional to [AscH−]. The latter term is explained by direct oxidation of the organic substrate by the primary dioxygen adduct of CuI, CuO. For [MeCN] < 0.7M, a gradual and pH‐dependent transformation of this rate law and deviation from the first‐order dependence on [O2] is indicated.
Isomerization of Olefins Catalyzed by the Hexaaquaruthenium(2+) Ion. Preliminary communication
Authors: Karlen Thomas , Ludi Andreas 
Published: December 2004

AbstractIsomerization of olefins, in particular the useful transformation of allyl to vinyl ethers is catalyzed by the hexaaquaruthenium(2+) ion, producing the (E)‐isomers under mild conditions.
Photochemical Synthesis and Some Reactions of 7‐Oxa‐and 7‐Thiatricyclo[3.2.1.03,6]octan‐2‐ones
Authors: Gebel Rolf‐Christoph , Margaretha Paul 
Published: December 2004

AbstractIrradiation (λ = 350 nm) of newly synthesized 2‐acetyl‐ or 2‐methyl‐2‐(alk‐2‐enyl)furan‐3(2H)‐ones 1 and 2‐acetyl‐ or 2‐methyl‐2‐(prop‐2‐enyl)thiophen‐3(2H)‐ones 2 affords the corresponding 1‐acetyl‐ or 1‐methyl‐substituted 7‐oxa‐ and 7‐thiatricyclo[3.2.1.03,6]octan‐2‐ones 10 and 11, respectively, via regioselective intramolecular [2 + 2] photocycloaddition in 65–95% yield (Scheme 2). The 1‐acetyl‐substituted O‐derivatives 10b and 10c undergo ring opening on treatment with MeONa in MeOH at–78° to afford stereoselectively methyl 3‐exo‐acetyl‐2‐oxabicyclo[3.2.0]heptane‐7‐endo‐carboxylates 12b and 12c, respectively, while a 2:1 diastereoisomeric mixture of methyl 3‐acetyl‐2‐thiabicyclo[3.2.0]heptane‐7‐endo‐carboxylates 13 and 14 is obtained from the corresponding S‐derivative 11b. The outcome of the Huang‐Minlon reduction of the 1‐methyl‐substituted ketones 10a and 11a is again influenced by the heteroatom in the tricycle. While 1‐methyl‐7‐oxatricyclo[3.2.1.03,6]‐octane (15) is the only product from the corresponding oxatricyclooctanone 10a, a 1:2 mixture of 1‐methyl‐7‐thiatricyclo[3.2.1.03,6]‐octane (16) and 3‐methylbicyclo[3.1.1]hept‐2‐ene‐6‐endo‐thiol (17) is obtained from the analogous S‐compound 11a, both products stemming from a common carbanion precursor.