摘要:

The Importance of the Cycloaracylation Process for the Synthesis of Modern FluoroquinolonesOver the last decade the fluoroquinolones have been introduced worldwide in a new antibacterial therapy in hospitals and in general practice. Up until the end of the 1970's the quinolones and fluoroquinolones were predominantly prepared by the Gould‐Jacobs reaction which has now been largely superseded by the cycloaracylation process discovered at Bayer. Through this process, highly active 1‐cycloalkyl‐, 1‐tert.‐alkyl‐, 1‐aryl‐, 1‐amino‐, as well as new 1,2‐, 1,8‐ and 2,3‐bridged quinolones were accessible for the first time. The preparative importance of the cycloaracylation process for the construction of modern fluoroquinolone antiinfectives will be

ISSN:0941-1216    

DOI:10.1002/prac.19933350502

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

Abstract2‐Hydroxy‐6‐alkyn‐5‐ones3, 1‐hydroxy‐5‐alkyn‐4‐ones4, and 1‐hydroxy‐6‐alkyn‐5‐ones5are conveniently obtained in excellent yields through a highly selective monoaddition of an 1‐alkynyllithium compound2to γ‐valerolactone(1a), γ‐butyrolactone(1b)or δ‐valerolactone(1c). They are oxidized by pyridinium dichromate or Jones reagent to the corresponding acetylenic 1,4‐diketones6, 4‐oxo carboxylic acids

ISSN:0941-1216    

DOI:10.1002/prac.19933350503

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

Dideoxy Ribonucleosides by Fusion MethodThe dideoxy nucleosides2,4and6are synthesized from the 1‐O‐acetyl‐2,3‐dideoxyribose derivatives1,3and5by fusion with chlorinated purines and other nitrogen heterocycles at 110–120°C without added catalyst. The1H‐NMR and13C‐NMR spectra of the compo

ISSN:0941-1216    

DOI:10.1002/prac.19933350504

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

The Buffering Effect of the Oceans upon Atmospheric Carbondioxide ContentThe influence of the oceans upon atmospheric CO2‐content by an irreversible flow equilibrium is studied. Besides the already disclosed influences of pH value and calcium ions concentration in the seawater an essential effect of the total CO2‐passage through the atmosphere steps forth. Respecting the negligible small amount (lesser than 1%) of anthropogenic carbondioxide in comparison to the annual CO2‐flux through the atmosphere any additional greenhouse effect by human activity is exc

ISSN:0941-1216    

DOI:10.1002/prac.19933350505

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

Dependence on the Substituents of the Photoconduction from ArylaminesAromatic amines are often used as charge transporting agents in electrophotographic two‐layer‐systems. Structure‐property‐relations of this substance class are discussed on the basis of homogeneously sensitized polycarbonat‐layers containing derivatives of anilines. Substituent variation of the actinic compounds has a significant influence on the electrophotographic sensitivity. Correlations between Hammett substituents constants and electrophotographic sensitivity are useful for the preselection of arylamin structures. Dibenzylamino groups lie out of these correlations and induce an unexpected high photoconductivity. This fact was investigated by cyclovoltammetric measurements of 22 various dibenzylanilines. Low half‐peakpotentials and reversible one‐electron oxidation steps of dibenzylanilines are necessary for outstanding photoconduct

ISSN:0941-1216    

DOI:10.1002/prac.19933350506

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

Free Radical Reactions of N‐Heterocyclic Compounds. XI. ESR‐Study of Radicals of 3‐Methyl‐pyrazolin‐5‐onesThe oxidation of 1,4‐substituted 3‐methylpyrazolin‐5‐ones (1a–p) led to pyrazolinonyl radicals (2a–p), which were detected directly or after trapping with nitrosobenzene as phenyl nitroxides. In a few cases, the products of oxidation of pyrazolin‐5‐ones (1) with electron‐withdrawing groups in 4‐position by peroxy radicals were endo cyclic nitroxides (8), which were al

ISSN:0941-1216    

DOI:10.1002/prac.19933350507

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

Δ16‐20‐Ketosteroids by C2‐Elongation from Δ16‐17‐Substituted SteroidsReactions of corticoid precursor steroids with a Δ16‐double bond and iodine, trimethylsilyl, tributylstannyl or trifluoromethanesulfonyloxy groups in 17‐position were studied with the aim of introducing an acyl substituent in 17‐position. Starting with the 17‐trimethylsilyl compounds, using acyl chlorides and AlCl3as a catalyst, a mixture of chlorinated compounds were obtained, among others. Better results gave palladium‐catalyzed reactions, such as the cross‐coupling of 17‐tributylstannyl compounds with acyl chlorides or the substitution of the 17‐iodides or the 17‐triflates by vinyl ethers. In the reaction of the 17‐iodides, different protecting groups are tolerated; thus this method is of general use. No Δ16‐17‐triflates were obtained by the reaction of androsta‐4‐ene‐3, 17‐dione or androsta‐1,4‐diene‐3, 17‐dione with trifluoromethanesulfonyl anhydride. This is a limitation of the triflate method,

ISSN:0941-1216    

DOI:10.1002/prac.19933350508

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

Synthesis of „Ethyl‐Brahmanol”︁The synthesis of the title compound (11) from ethylapopinene (5) by oxydation to the epoxide (6), rearrangement to “ethyl‐α‐campholene aldehyde” (7) and its aldol condensat

ISSN:0941-1216    

DOI:10.1002/prac.19933350509

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractThe dediazoniation of 2,5‐di‐(n‐butoxy)‐4‐morpholino‐benzenediazonium tetrafluoroborate (1) sensitized by zinc phthalocyanine tetrasulfomorpholid (ZnPcTSM) is studied in di‐n‐butylphthalate. The life‐time of singlet‐excited ZnPcTSM (τs= 3.0 ns) is not decreased by1whereas the static fluorescence at 689 nm is quenched. Thus, a ground‐state complex is formed, Keq= 1730 M−1showing an absorption band at 714 nm. A similar complex is formed with mono‐n‐butylphthalate being present if di‐n‐butylphthalate was not distilled in a good vacuum (1 torr), Keq= 1545 M−1. The decay of the triplet state in the presence of1is adequately treated as a reaction from the triplet‐excited ground‐state complex. Keqof the ZnPcTSM‐diazonium salt complex is also obtained from quantum yields of the sensitized dediazoniation. A rather low intersystem crossing quantum yield of the complex amounting to 0.17 is deduced. ZnPcTSM is also bleached, but much weaker than expected for an oxidative electron transfer.The system works well – even under air – in dibutylphthalate mic

ISSN:0941-1216    

DOI:10.1002/prac.19933350510

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

ISSN:0941-1216    

DOI:10.1002/prac.19933350511

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY