摘要:

AbstractZur Abklärung von stereochemischen und rückoxydativen Problemen an vier verschiedenen methylsubstituierten 5,6,7,8‐Tetrahydropterinen wurden diese durch Umkristallisation gereinigt und die Reinheit der kristallinen Substanzen durch DC. in basischem Milieu unter Stickstoff, GC., NMR. und MS. festgestellt. Die reinen Substanzen wurden silyliert und wiesen je nach Reaktionsbedingungen verschiedene Silylierungsgrade auf. Die erhaltenen Derivate wurden durch kombinierte GC./MS. getrennt und identifiziert. Der Ort der Silylierung im hydrierten Pyrazinring wird vorwiegend von sterischen Faktoren bestimmt und erweist sich als unabhängig von der Basizität der reaktiven Zentren. Das Gemisch von vier Tetrahydro‐ und zwei Dihydropterinen konnte durch hochauflösende Glaskapillarchromatographie getrenn

ISSN:0018-019X    

DOI:10.1002/hlca.19740570602

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY

摘要:

AbstractOn oxygenation of alcoholic solutions of tetraethylenepentamine cobalt(II) two isomeric forms of [(tetren)CoO2Co(tetren)]4+are obtained in which the configuration of the pentadentate ligand is either α or β. The binuclear complex can be crystallized as thiocyanate or as perchlorate. Oxygenation at 35° produces the pure α isomer. At lower temperature a mixture of α and β is obtained. The isomers differ slightly in their absorption spectra and their reactivity. The ligand configuration has been elucidated by transforming the perchlorates into the [ZnCl4]2−salts of the corresponding mononuclear chelates [Co(tetren)Cl]2+. The latter have also been prepared starting from a compound of known configuration according to the literature. The IR. spectra of the α and β forms differ characteristically in the NH stre

ISSN:0018-019X    

DOI:10.1002/hlca.19740570603

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY

摘要:

AbstractThe reaction sequences shown in schemes 3 and 4, represent a new method for the synthesis of a substituted pyridone‐system, starting from a vinylogous amide or thioamide and malonic este

ISSN:0018-019X    

DOI:10.1002/hlca.19740570604

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY

摘要:

AbstractTwo novel methods for the synthesis of terminal acetylenic sugars, both involving a chain extension by one carbon unit, are described. In the first procedure, an aldehydo‐sugar is treated with dibromomethylenetriphenyl‐phosphorane, then withn‐butyllithium and finally with water. The second method involves an one‐step reaction between an aldehydo‐sugar and dimethyl diazomethylphosphonate. The acetylenic sugars obtained are valuable synthetic intermediates for the preparation of heterocyclic C‐nucleosides by 1,3‐dipolar cycloaddition reactions and some examples of syntheses of this type are described. Treatment of keto‐sugars with dimethyl diazomethylphosphonate led to an intermediate carbenoid species which reacted by insertion into a CH bond in one case and underwent nucleophilic attack by a methoxy group

ISSN:0018-019X    

DOI:10.1002/hlca.19740570605

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY

摘要:

AbstractThe mass spectral decomposition of the 1‐tetralol derivatives2, 3and4in view of the retroDiels‐Alderreaction is investigated, for which deuterated derivatives, high resolution data and metastable peaks were used. By these studies it follows that the decyclisation reaction on ring A possesses the character of a retroDiels‐Alderreaction only in some part. The main mass spectral degradation is forced by the substituents placed th

ISSN:0018-019X    

DOI:10.1002/hlca.19740570606

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY

摘要:

AbstractThe photoelectron spectra of spiro[3.4]octane (1), spiro[3.4]octene‐5 (2), spiro[3.4]‐octa‐5,7‐diene (3), spiro[4.4]nonene‐2 (4) and spiro[4.4]nona‐2,4‐diene (5) have been recorded. The first bands of these spectra are correlated with orbitals which are π‐orbitals,Walshorbitals resp. linear combinations of both. Our assignment is based on a qualitative ZDO‐model, it is in satisfactory agreement with the results of extendedHückelcalculations. The interaction found in2and3is of similar magnitude as the one in4and5and considerably less than that in homo

ISSN:0018-019X    

DOI:10.1002/hlca.19740570607

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY

摘要:

AbstractLosod, a new type of crystalline hydrated sodium aluminosilicate, Na12Al12Si12O48· q H2O, has been prepared from reaction mixtures containing bulky quaternary alkylammonium ions, particularly azonia‐spiro[4.4]nonane, besides sodium ions. Losod crystallizes from batches with a low sodium content (Na/Al ≤ 1 and Si/Al ≈︁ 1). The quaternary ammonium hydroxide primarily serves as a source of hydroxide ions and is not incorporated into the zeolite crystals. These bulky bases provide a useful means for controlling the alkalinity of the system independently of the concentration of the necessary cations built into the zeolite.The crystals of Losod are hexagonal (a= 12.91 andc= 10.54 Å) and the proposed framework structure shows a polytypic relationship to sodalite and cancrinite. Losod has reversible sorption and ion exchange properties typical of a small‐pore zeolite and in essential agreement with the propose

ISSN:0018-019X    

DOI:10.1002/hlca.19740570608

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY

摘要:

AbstractThis paper reports 261 substituent increments for the1HNMR. chemical shifts (solvent: CDCl3) of the 18‐ and 19‐methyl protons of 9β, 10α(retro)‐steroids relative to 5β,9β,10α,‐androstane. The increments were calculated by a least‐squares procedure from 1334 spectra of 759 di

ISSN:0018-019X    

DOI:10.1002/hlca.19740570609

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY

摘要:

AbstractIn Part II of this series we report 292 substituent increments for the1H‐NMR. chemical shifts (solvent: CDCl3) of the 18‐ and 19‐methyl protons of 9α,10β(normal)‐steroids relative to 5α,9α,10β,‐androstane. The increments were calculated by a least‐squares procedure from 988 spectra of 681 di

ISSN:0018-019X    

DOI:10.1002/hlca.19740570610

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY

摘要:

AbstractMethyl groups in positions adjacent to an olefinic double bond can be metalated withoutcis/transisomerisation. On the other hand configurational changes can be brought about via metalotropy; under equilibrium conditions theZisomers (metalcisto an alkyl in β position) predominate overwhelmingly. This behaviour opens new stereoselective routes of high preparative utility

ISSN:0018-019X    

DOI:10.1002/hlca.19740570611

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY