摘要:

AbstractPositive and negative secondary‐ion‐mass spectra of poly(2‐hydroxyethyl methacrylate), poly(2‐hydroxypropyl methacrylate) and both polymers after modification with D2O and propionyl chloride are presented. The spectra were obtained with a Time‐of‐Flight Secondary‐Ion‐Mass Spectrometer. The structures of typical ions in the mass range 10‐150 amu are given and the intensities of these ions were used to obtain quantitative information about the ion formation processes. Furthermore, the spectra of poly(2‐hydroxyethyl methacrylate), poly[2‐(propionyloxy)ethyl methacrylate] and four copolymers of 2‐hydroxyethyl methacrylate and 2‐(propionyloxy)ethyl methacrylate are compared to provide quantitative results on ion‐formation efficiency and/or stability. The results of this study can be used to study the kinetics of the reaction of propionyl chloride with poly(2‐hydroxyeth

ISSN:0165-0513    

DOI:10.1002/recl.19901090602

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractCrystals of 1‐amino‐1‐phenylcyclopropane, C9H11N, grown from the liquid are mono‐clinic, space groupP21/n, a= 27.565(5),b= 6.047(6),c= 18.024(4) Å, β = 96.76(2) = (110 K).Z= 16. The finalRfor 4086 independent observed reflections is 0.057. The 4 molecules in the asymmetric unit have the bisecting conformation for the phenyl group and thes‐transpyramidal conformation for the NH2group. The average distal bond length in the cyclopropane ring is 1.503(4) Å; the average vicinal length is 1.520(3) Å (corrected f

ISSN:0165-0513    

DOI:10.1002/recl.19901090603

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe preparation of two13C‐labelled isotopomers of spheroidene, the carotenoid bound in the photosynthetic reaction center ofRhodobacter sphaeroides, is described.All‐E(14′‐13C)‐spheroidene has been synthesized in high yield and purity and with more than 98%13C incorporation starting from (2‐13C)acetonitrile; similarly, all‐E(15′‐13C)spheroidene has been obtained starting from (I‐13C)acetonitrile. The spectroscopic properties of all‐Espheroidene and its (14′‐13C)‐ and (15′‐13C)isotopomers are discussed. The mass spectra of the labelled compounds reveal that toluene is eliminated mainly from the central part of the molecule. Analysis of the ′H‐NMR spectrum of all‐E(15′‐13C)spheroidene gives a value of 14.0 Hz for the1H ‐1H

ISSN:0165-0513    

DOI:10.1002/recl.19901090604

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractA series of 4‐substituted Hantzsch 1,4‐dihydropyridines has been synthesized. Substituents at the 4‐position include 2‐pyridyl, 2‐imidazolyl, and 1‐methyl‐2‐imidazolyl. By use of various acetoacetic ester derivatives methoxy and methylthio groups have been introduced in the ester side chains at the 3,5‐positions. A representative example is bis(2‐methoxyethyl) 1,4‐dihydro‐2,6‐dimethyl‐4‐(1H‐imidazol‐2‐yl)‐3,5‐pyridinedicarboxylate (5h). The crystal structure of bis‐[(2‐methylthio)ethyl] 1,4‐dihydro‐2,6‐dimethyl‐4‐(1H‐imidazol‐2‐yl)‐3,5‐pyridinedicarboxylate (5i) has been determined. The imidazole group at the 4‐position is located in a pseudo‐axial position. In the13C‐ and1H‐NMR spectra line doubling is seen in the 4‐imidazole‐substituted derivatives. This is apparently the result of slow tautomerization. Various complexes with Zn(NO3)2· 4H2O have been prepared but no crystal structures could be obtained. These 1,4‐dihydropyridines have little capacity, either in the presence or absence of metal ions, to carry out reductions. This may be the result of a stereoelectronic effect caused by t

ISSN:0165-0513    

DOI:10.1002/recl.19901090605

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractAlkaline decarboalkoxylative cyclization of 1.4.5.6‐tetrahydropyridine 3b does not lead to dl‐18‐nor‐18,19‐dihydroantirhine 1b [C(3)H‐C(15)H trans relationship] but to the corresponding 3‐epi analogue 2b [C(3)H‐C(15)H ci

ISSN:0165-0513    

DOI:10.1002/recl.19901090606

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

Abstract2‐Alkyliden‐1,3‐dioxolanes can be prepared surprisingly easily from the corresponding 2‐bromoacetals by dehydrobromination with potassium tert. butoxide. The method has a wide scope and gives access to ketene acetals which cannot be prepared by other methods. The application of mono substituted cyclic ketone acetals in the lewis acid catalyzed stereoselective formation of cis oxetanes from aldehydes is illu

ISSN:0165-0513    

DOI:10.1002/recl.19901090607

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19901090609

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19901090610

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19901090601

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY