摘要:

AbstractESR. and, in part, ENDOR. studies are reported on the radical anions of 5,5′‐and 6,6′‐biazulenyl (1and2, resp.), as well as on their 1, 1′, 3, 3′‐tetradeuterioderivatives (1‐d4and2‐d4). The reduction processes of1and2leading to these radical anions (\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}}$\end{document}and\documentclass{article}\pagestyle{empty}\begin{document}$ 2^{\ominus \atop \dot{}}$\end{document}) and the dianions () have been investigated by polarography and cyclic voltammetry. The half‐wave reduction potential of1and the π‐spin distribution in\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}}$\end{document}are consistent with the model of two weakly interacting azulene π‐systems, whereas the analogous findings for2and\documentclass{article}\pagestyle{empty}\begin{document}$ 2^{\ominus \atop \dot{}}$\end{document}point to a strong interaction between two such systems. This difference can be traced to the distinct inequality ∥c65∥ « ∥ c66∥ in the LCAO coefficients c6μat the centres

ISSN:0018-019X    

DOI:10.1002/hlca.19800630802

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractThe radical cations and anions of naphtho [1,8‐cd]‐[1,2,6]thiadiazine(1)and 6,7‐dihydroacenaphtho [5, 6‐cd]‐[1,2,6]thiadiazine(2), as well as the radical anion of acenaphtho [5, 6‐cd]‐[1,2,6]thiadiazine(3)have been characterized by ESR. spectroscopy. The π‐spin distributions in the radical cations\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\oplus \atop \dot{}}$\end{document}and\documentclass{article}\pagestyle{empty}\begin{document}$ 2^{\oplus \atop \dot{}}$\end{document}strongly resemble those in the iso‐π‐electronic phenalenyl radical. A prominent feature of the radical anions\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}}$\end{document},\documentclass{article}\pagestyle{empty}\begin{document}$ 2^{\ominus \atop \dot{}}$\end{document}and\documentclass{article}\pagestyle{empty}\begin{document}$ 3^{\ominus \atop \dot{}}$\end{document}is the substantial localization of the π‐spin population on the thiadiazine fragment. These findings are satisfactorily accounted for by HMO models using convention

ISSN:0018-019X    

DOI:10.1002/hlca.19800630803

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractWhen theHammett‐Taftequation log (k/ko)=ρq· σ 1qis applied to the solvolysis of the 3‐substituted propyl bromides6a‐6iin ethanol/water 4:1(v/v)logkcorrelates linearly with σ 1qexcept in cases where R exerts an anchimeric effect. The reaction constant ρqfor6is − 0.12 and is typical for a nucleophilic solvent‐assistedksprocess at a primary C‐atom. The tertiary halides1and3, however, which react with little or no nucleophilic solvent assistance,i.e.bykcprocesses, lead to larger ρqvalues of −0.71 and −1.14, respectively. The reaction constantpqis therefore a sensitive gauge for charge development in the transition state for solvolys

ISSN:0018-019X    

DOI:10.1002/hlca.19800630804

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractTwo new sesquiterpenoids, nakafuran‐8(1)and −9(8), have been isolated from the marine spongeDysidea fragilisand from its prey, the nudibranchsHypselodoris godeffroyanaandChromodoris maridadilus.The structures were established by spectral analysis and chemical transformations. Both compounds possess antifeedant properties when assayed in the laboratory against common reef fishes,Chaetodon

ISSN:0018-019X    

DOI:10.1002/hlca.19800630805

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractAmines are converted in good to excellent yields to phenylsulfides or phenyl‐selenidesvianucleophilic displacement on the corresponding ditosylamides. The conversion of (−)‐(S)‐1‐phenylethylamine to the chiral phenylsulfide6was found to proceed with inversion of configuration. A simple one‐pot procedure for the preparation of ditosylamides

ISSN:0018-019X    

DOI:10.1002/hlca.19800630806

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractThe transformations of isomeric 1,3‐chloroalcohols1–4, with cyclohexane skeleton, were studied in aqueous solution containing barium hydroxide. As regards the compounds withcis‐configuration,1gives the oxetane5by intramolecular nucleophilic substitution, while3gives the unsaturated alcohols7and8by elimination. In the case of thetrans‐isomers2and4, fragmentation reactions occur in competition with elimination. The main reaction kinetic parameters of the transformations of the four compounds were det

ISSN:0018-019X    

DOI:10.1002/hlca.19800630807

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractThe stereospecificcis‐hydroxylation of 1‐(2,3‐dideoxy‐β‐D‐glyceropent‐2‐enofuranosyl)thymine(1)into 1‐β‐D‐ribofuranosylthymine(2)by osmium tetroxide is described. Treatment of 2′,3′‐O,O‐isopropylidene‐5‐methyl‐2,5′‐anhydrouridine(8)with hydrogen sulfide or methanolic ammonia afforded 5′‐deoxy‐2′,3′‐O,O‐isopropylidene‐5′‐mercapto‐5‐methyluridine(9)and 2′,3′‐O,O‐isopropylidene‐5‐methyl‐isocytidine(10), respectively. The action of ethanolic potassium hydroxide on 5′‐deoxy‐5′‐iodo‐2′,3′‐O,O‐isopropylidene‐5‐methyluridine(7)gave rise to the corresponding 1‐(5‐deoxy‐β‐D‐erythropent‐4‐enofuranosyl)5‐methyluracil(13)and 2‐O‐ethyl‐5‐methyluridine(14).The hydrogenation of2and its 2′,3′‐O,O‐iso

ISSN:0018-019X    

DOI:10.1002/hlca.19800630808

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractVarious two‐electron reduced flavin derivatives have been investigated by natural abundance13C‐NMR. spectroscopy. Some selectively13C‐enriched compounds were synthesized to ensure the assignment of some of the quaternary C‐atoms of the flavin molecule. Addition of two electrons to oxidized flavin leads to upfield shifts of all resonances except for those due to C(5a), C(9) and C(10′α). The largest upfield shift is observed for C(4a). Also some direct and two‐bond coupling constants are reported. Theoretical calculations by INDO show that a rather good correlation exists between the calculated π‐electron densities and the observed chemical shifts of the two‐electron reduced molecule. For the oxidized molecule, the correlation is less satisfactory. Most substitution effects are additive, but some deviations in some compounds are observed indicating structural differences between the compounds in question.The chemical shifts are also discussed in terms of the chemical reactivity of the oxidized and reduce

ISSN:0018-019X    

DOI:10.1002/hlca.19800630809

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractTheSpiesecke&Schneiderrelationship between charge and13C‐chemical shifts has been widely used in recent years. In the present work a set of 20 organic compounds with a total of 50 different chemical shifts has been investigated with respect to the applicability of this relation. Attempted correlation between13C‐shifts and charges indicated that the proportionality constant highly depends on the MO‐method used. In order to circumvent these problems paramagnetic shifts were computed using standard techniques. The effect of including a diamagnetic shift correction is disc

ISSN:0018-019X    

DOI:10.1002/hlca.19800630810

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

The Photoinduced Cleavage of Conjugated γ, δ‐Epoxyenones: UV.‐Irradiation of 5,6‐Epoxy‐3, 4‐didehydro‐5,6‐dihydro‐β‐iononeOn1n, π*‐excitation (λ ≥ 347 nm) in pentane or CClF2CFCl2(E)‐1is isomerized to the dihydrofurane (E/Z)‐2as well to the ethers3and5.Besides these products the isomeric cyclopropane derivative (E)‐4and the acetal6are obtained in methanol. The detection of6indicates the formation of an intermediate ketoniumylideawhich may give6by addition of methanol. − On1π, π*‐excitation (λ=254 nm) in acetonitrile‐d3, CClF2CFCl2or pentane (E)‐1yields almost exclusively (E)‐2.In methanol6is obtained in a

ISSN:0018-019X    

DOI:10.1002/hlca.19800630811

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY