摘要:

Photochemistry of Acylazides. III. Direct and Sensitized Photolysis of p‐Trimethylsilylbenzoylazide in the Fluid Phase and in Polymeric LayersThe photochemistry of the title compound in cyclohexane was investigated by direct and sensitized excitation, respectively. The only products which could be detected by means of HPLC were the rearrangement product isocyanate from the singlet azide and the insertion product into the solvent via the singlet nitrene, respectively. Products via the triplet states were not formed by direct photolysis. The generally high quantum yields of the photolysis of the acylazide1are strongly dependent on the concentration. At 0.1 M the quantum yield amounts to 4.The photolysis was sensitized by several triplet generators creating the abstraction products as main products. But also insertion products were formed via the triplet azide. From the results a triplet ground state of the nitrene is postulated. The sensitization can be realized also by electron donors like diphenylanthracene, pyrene or perylene. An electron transfer to1is assumed. The products of this sensitization are the same as via the direct photolysis.The results in solutions can be applied to polymers. The modification of polymers (silylation by the nitrene formed) is possible in this wa

ISSN:0021-8383    

DOI:10.1002/prac.19893310202

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractSixteen acetylenic amine oxides (5a–p) were prepared by the oxidation of the corresponding tertiary amines (4a–p) with m‐chloroperbenzoic acid. The N‐oxides are thermally unstable and undergo a rearrangement when stirred in an inert solvent yielding O‐allenyl hydroxylamines (6). The rearrangement proceeds by an intramolecular cyclic

ISSN:0021-8383    

DOI:10.1002/prac.19893310203

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

ISSN:0021-8383    

DOI:10.1002/prac.19893310204

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

Flavylium Salts as Probes for the Characterization of Anionic MicellesFlavylium salts are suitable probe molecules for the fluorimetric investigation of the critical micelle concentration (CMC); for the absorption‐spectroscopic investigation of the surface potential; and also the microacidity in the Stern‐layer of anionic micelles. The reaction rates of the hydrolytic cleavage of the 7‐hydroxy‐4′‐methoxyflavyliumion1aand the equilibrium between1aand the 2,4‐dihydroxy‐4′‐methoxychalcone5aformed were studied in acidic water solutions and in micellar surfactant solutions. Both measurements resulted in comparable values of the microacidity on the surface of the sodium dodecylsulfate micelles (SDS). The calculated surface‐potential of SDS‐micelles corresponds to literature data.The surface‐potentials of p‐dialkylbenzenesulfonate micelles (p‐DABS) depend on the structure of these surfactan

ISSN:0021-8383    

DOI:10.1002/prac.19893310205

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

Abstract3‐Arylacrylonitrile‐2‐thiocarboxamides (1a–d) reacted with S‐methylisothiourea to give 4‐amino‐6‐aryl‐2‐methylmercaptopyrimidine‐5‐carbonitriles (3a–d). The products3a–dwere also obtained via the reaction of 3‐arylacrylonitrile‐2‐carbonitriles (4a–d) with S‐methylisothiourea. Compounds4a–dreacted with thiourea and urea to yield 4‐amino‐6‐aryl‐2‐mercaptopyrimidine‐5‐carbonitriles (5a–d) and 2‐hydroxy derivatives (5e–h) respectively. Oxidation of5a–dwith hydrogen peroxide afforded5

ISSN:0021-8383    

DOI:10.1002/prac.19893310206

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

ISSN:0021-8383    

DOI:10.1002/prac.19893310207

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

Substituent Effects in13C‐N.M.R. Spectra of Diastereomeric Chalcone Dihalogenides. VIII. Investigations of α‐ and β‐Halogene Dihydrochalcones and Calculation of13C‐chemical Shifts of Diastereomeric Chalcone Dihalogenides and Chalcone HalogenohydrinsThe chemical shifts of C‐α and C‐β in the13C‐n.m.r. spectra are determined and compared with calculated values from an incremental system and Taft relationship. The correlations are extended for erythro and threo isomers of halohydrins and diastereometric dihalogenides6–18.The chemical shifts of C‐α and C‐β atoms of6–18are described in the dependence of the shifts calculated by an incremental system. Excellent correlations allowed the computation of chemical shifts of C‐α and C‐β for diastereomeric α,β‐disubstituted dihydrochal

ISSN:0021-8383    

DOI:10.1002/prac.19893310208

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractEthinylestradiol (1) was converted into the corresponding 6‐oxo derivative7by a short and simple procedure involving acetate10and ketone11. Phase transfer catalyzed esterification of compound7with propane‐2‐sulfonyl chloride gave sulfon

ISSN:0021-8383    

DOI:10.1002/prac.19893310209

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractAlkylation of 2‐morpholino‐cycloalken‐1‐carbothionic acid anilides1and2with 1,3‐dibromopropane in a two‐phase system leads to 1‐morpholino‐cycloalken‐3‐aryl‐tetrahydro‐1,3‐thiazine‐2‐ylidene3and4. Reactions of 2‐morpholino‐cyclopenten‐1‐carbothionic acid anilides5and 3‐morpholinothiocinnamic acid anilides8with 1,2‐dibromoethane yield 1‐morpholino‐cyclopenten‐3‐aryl‐thiazolidine‐2‐ylidene7and 2‐(2′‐phenyl‐2′‐oxo‐ethylidene‐3‐aryl)thiazolidine9, respectively. Alkylation of 1‐indanone‐ and 1‐tetralone‐2‐carbothionic acid anilides11and12with dihalogenoalkanes yield 1‐oxo‐indanylidene

ISSN:0021-8383    

DOI:10.1002/prac.19893310210

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

Dithiocarboxylic Acids, Dithiocarboxylic Esters, or Thiocarboxylic Amides by Reaction of Methylene‐active Chloromethyl Compounds with SulfurWith a mixture of sulfur and amine in DMF at room temperature halomethyl compounds (1,5–10) can be oxidized to give thiocarboxylic acids (2,11–16) and their derivatives (3,4,17–35). We studied this reaction in detail especially with chloroacetic derivatives (11–15) or chloromethyl heterocycles (16) formally derived from chloroacetic acid.The resulting thiooxalic acid derivatives (11–27) represent activated acids and very useful C2‐synthons, especially for the synthesis of heterocycles.Oxidation in the presence of triethyl amine leads to dithiocarboxylates (11–16) which can be alkylated to dithioesters (17–27) in high yields.As a rule, with different primary and secondary amines instead of tertiary amines these dithiocarboxylates or dithiocarboxylic esters can be transformed already at low temperatures to t

ISSN:0021-8383    

DOI:10.1002/prac.19893310211

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY