摘要:

Structure‐Activity/Selectivity Correlation of Oxidation CatalystsVarious reactive forms of oxygen are active in the selective oxygen functionalization of olefins and aromatic compounds.These forms are different on different crystal faces of transition metal oxides as shown by their different cation‐oxygen bond lengths. Therefore, face specifity of transition metal oxides as catalysts can be expected for the selective oxidation of hydrocarbons.Furthermore, the reactivity of the framework oxygen in the transition metal oxides for selective oxygen functionalization of hydrocarbons is dependent on the nature of the catalytic cycle (one‐ or two‐electron‐processes).Therefore, structure sensitivity of oxidation catalysts on the selectivity of transition metal oxides as oxidation catalysts is possible. Starting from this concept the following phenomena of the activity/selectivity relations are discussed for the most important industrial oxidation catalysts:—ensemble effects on the selectivity of supported Ag catalysts for the oxidation of ethylene to ethylenoxide.—face specifity of multicomponent Bi/Mo‐oxide catalysts in the selective oxidation of propylene to acrolein and in the ammoxidation of propylene.—structure sensitivity of V2O5‐containing catalysts in the oxidation of

ISSN:0021-8383    

DOI:10.1002/prac.19913330402

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

ISSN:0021-8383    

DOI:10.1002/prac.19913330403

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

About the Reversible Conversion of 3‐Diethylamino‐5‐phenyl‐1,2,4‐dithiazoliumhalometallates into Metal Chelates of 3‐(Thio)benzoyl(thio)ureasRedox reactions of 3‐diethylamino‐5‐phenyl‐1, 2,4‐dithiazolium halometallates1a‐eand metal chelates (M = CuII(2 A), CoII(2 C), NiII(2 F)) of 3‐thiobenzoylthioureat was studied by cyclic voltammetry.1are converted by reduction into2.The mechanism of the oxidation of2 A,C,Finto1a,d,eis dependent on the central ion.On formation of1 afrom copper(II) chelates of 3‐benzoylthiourea3 Aby means of thionylchloride as well as by electrochemical oxidation 3‐benzoylureas

ISSN:0021-8383    

DOI:10.1002/prac.19913330404

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

Stereochemistry of N,N′‐Bis‐[3‐(o‐ethoxyphenoxy)‐2‐hydroxy‐propyl]‐ethylendiamineN,N′‐Bis‐[3‐(o‐ethoxyphenoxy)‐2‐hydroxy‐propyl]‐ethylene diamine (5), synthesized from racemic 1,2‐anhydro‐3‐O‐(o‐ethoxyphenyl)‐glycerol (1) and ethylene diamine (2) or N,N′‐dibenzyl ethylene diamine (3) crystallized in two fractions with different melting points. Both of these analytically pure products gave identical two spot tl‐chromatograms on achiral phases. Attempts were made to resolve the mixtures which proved to consist of configurative but not constitutive isomers. Optically

ISSN:0021-8383    

DOI:10.1002/prac.19913330405

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

Deep Coloured Systems with Oxalic Acid Substructure‐a Structural CorrectionBasing on a recent spectroscopic investigation the structure of earlier described deeply coloured systems derived from oxalic acid imidochlorides and thioacetamide has to be revised. Due to the poor solubility of these systems their spectroscopic characterization led to the misinterpretation as tetramethin‐bridged thiazolines1.By means of1H‐NOE‐Difference‐Spectroscopy of newly synthesized derivatives with lipophilic substituents a imidazolin‐thion substructure4has been found. Such an arrangement of the heteroatoms clearly reflects a 1,3‐rearrangement with participation of the oxali

ISSN:0021-8383    

DOI:10.1002/prac.19913330406

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

ISSN:0021-8383    

DOI:10.1002/prac.19913330407

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

AbstractThe alkylation of 4‐amino‐6‐methylpyrimidines (1a‐f) in DMSO or nitrobenzene at room temperature affords the1N‐alkylated products2a‐h. Treatment of1a‐cwith an excess of methyl iodide in the presence of powdered alkali metal hydroxides/DMSO gives the pyrimidinium salts2g,i,j.Carbon‐13 n.m.r. and X‐ray studies have shown that in the case of compounds2the polymethine struc

ISSN:0021-8383    

DOI:10.1002/prac.19913330408

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

ISSN:0021-8383    

DOI:10.1002/prac.19913330409

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

AbstractSynthesis of two mammalian gonadoliberin analogs, [Gln1]GnRH and [Glu1]GnRH, in solution by the peptide segment coupling of the [(2 + 4) + 4]type has been described.

ISSN:0021-8383    

DOI:10.1002/prac.19913330410

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

Cycloaddition Elimination Reactions of 4‐Aryl‐5‐arylimino‐1,2,4‐dithiazolidin‐3‐ones (Mustard Oil Oxides)4‐Aryl‐5‐arylimino‐1,2,4‐dithiazolidin‐3‐ones (1) react with isocyanates, isothiocyanates, and cyanic acid esters by exchange of the COS‐part from1affording thiadiazole and dithiazole derivatives4,5,6or12. The reaction products are able to give further exchange reactions. Ring opening of 2‐substituted 4‐aryl‐5‐arylimino‐1,2,4‐thiadiazolin‐3‐ones (4) and ‐3‐thiones (6) yields thio‐ and dithiobiurets (7,8) with aryl substituent in 3‐position. Oxidation of dithiobiurets, generated from6, af

ISSN:0021-8383    

DOI:10.1002/prac.19913330411

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY