摘要:

HydrogermylationsThis review is a survey of addition reactions of Ge‐H functional organogermanes RnGeH4‐n(R = alkyl and/or aryl; n = 1, 2 or 3) to unsaturated compounds (alkenes, alkynes, ketones, aldehydes, e

ISSN:0941-1216    

DOI:10.1002/prac.19923340602

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

Differences in the Total Oxidation of Organic Compounds on Heterogeneous Pt‐ and Pd‐CatalystsThe catalytic oxidation of selected organic compounds was studied on supported Pd and Pt catalysts and on massive wires. Unfunctionalized (Decane), unsaturated (dodecene, benzene), oxygen containing (1‐octanol, formaldehyde, acetone, n‐butylacetate, formic acid), nitrogen containing (aniline, pyridine), sulfur containing (thiophene) and chlorinated (1,2‐dichloroethane) hydrocarbons were used as model compounds. The relative activity of the metals for oxidation of the various compounds was determined from the turnover frequencies. While platinum is more active for the oxidation of the unfunctionalized, aromatic and chlorinated compounds, palladium is more active for nitrogen and sulfur containing compounds and for formic acid. No specificity is found for alkenes and compounds with a lower oxygen content. In the presence of octane, the unreactive pyridine is much more effectively oxidized than pyridine alone.There are distinct differences for the oxidation of octane/pyridine mixtures on bimetallic, mixed and pure Pt‐ and Pd‐catalysts. The bimetallic catalyst and the pure Pt‐catalyst dominate with respect to conversion and selectivity. The oxidation of linear alkanes on Pt correlates with the boiling point. Pd catalyzes the oxidation of lower hydrocarbons (C5) are better

ISSN:0941-1216    

DOI:10.1002/prac.19923340603

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractBy treatment of methyl 3β‐acetoxy‐7β‐hydroxy‐4,4,14‐trimethyl‐1‐oxo‐5α‐chol‐8‐en‐24‐oate3with p‐toluenesulfonyl chloride in pyridine methyl 3β‐acetoxy‐4,4,14‐trimethyl‐11‐oxo 19‐norchola‐5,7,9‐trien‐24‐oate1awas synthesized and its structure confirmed by spectral evidence. From 3β‐acetoxy‐19‐norlanosta‐5,7,9‐trien‐11‐one1bthe 7‐amino derivative1d, of which was prepared by nitration and selective c

ISSN:0941-1216    

DOI:10.1002/prac.19923340604

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

The Influence of Iodomethane on the Direct Synthesis of Poly(diphenylcarbosilane)The influence of the Ph2SiCl2/iodomethane molar ratio on the direct synthesis, structure and properties of the obtained oligomeric poly(diphenylcarbosilanes) C‐PPC/Me was investigated at molar ratios Ph2SiCl2:CH3I = 0,5; 1; 2; 4; 9.Increasing the CH3I‐concentration leads to an increase of the average molecular weights of the synthesized products and more side reactions. The formation of volatile hydrocarbons decreases the amount of CH3I and CH2Br2during the reaction and leads to the production of oligomeres with high polysilane character. The polycarbosilanes obtained were investigated by elemental analysis and characterized spectoscopically. Furthermore the weight and number averages Mwand Mnwere determined by gel‐permeation chromatography. They reflected the oligomeric character of this pro

ISSN:0941-1216    

DOI:10.1002/prac.19923340605

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractA number of novel thieno[2,3‐b]pyridines were prepared from the reaction of1with unsaturated haloalkanes, and by the reaction of the amino ketones9and10with DMF dimethylacetal or triethyl orthoformate. The synthesis of novel thieno[2,3‐c] and [3,2‐c]pyridines, and a thieno[2,3‐b;4,5‐b']dipyridine are also

ISSN:0941-1216    

DOI:10.1002/prac.19923340606

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

Electrocatalyzed Cyanomethylation of Azomethines: A New Synthesis for β‐AminonitrilesCertain Schiff‐bases (2–7) react in acetonitrile (1) at a Hg‐cathode in a new electrocatalyzed cyanomethylation method in good yields without side‐products to β‐aminonitriles (2a–7a). The synthesis is initiated by an electrochemical deprotonation of1by azomethine‐radical anions in catalytical amount to acetonitril anions (B−). During nucleophilic reaction of B−with2–7up to its complete consumption, the cyanomethylation synthon B− is regenerated in a cyclic, self‐reproducing process. Quantum chemical calculation in context with cyanomethylation product analysis permit mechanistical insights and exact prediction of suitable azomethines a

ISSN:0941-1216    

DOI:10.1002/prac.19923340607

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

On the Synthesis of 3‐Amino‐pyrroles by Thorpe‐Ziegler‐CyclizationN‐Aryl and alkylaminomethylene cyanacetic acid derivatives1react with α‐halogencarbonyl compounds2in the presence of potassium carbonate/sodium ethoxide to yield the substituted 3‐amino‐pyrroles6.Using the same principle of cyclization pyrrole derivatives6can also be obtained by reaction of β‐chloro‐ and β‐alkoxymethylenemalononitriles4with β‐aminocarbonyl compounds5.From the malononitrile derivatives1containing the methylthio group in the β‐position, and α‐halogen ketones7, the 2‐dicyanomethylene oxazolines8arise which undergo alkoholysis by treatment with sodium alkoxide to form the 3

ISSN:0941-1216    

DOI:10.1002/prac.19923340608

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractNitrobenzene, α‐nitronaphthalene, m‐dinitrobenzene, 1,3,5‐trinitrobenzene, m‐nitrobenzophenone, m‐nitrobenzonitrile, methyl m‐nitrobenzoate and m‐nitro diphenylsulphone can be hydroxylated with cumene or tert‐butyl hydroperoxide in dipolar aprotic solvents in the presence of strong bases. The hydroxyl group is introduced preferably in p‐position to the nitro group. Attempts to hydroxylate benzophenone, anthraquinone, 2‐ethyl anthraquinone, anthraquinone 2‐sulphonate, benzonitrile and diphenyl sulphone under the same conditions failed. 1‐Nitroanthraquinone delivered 1‐hydroxy, 1,2‐dihydroxy and

ISSN:0941-1216    

DOI:10.1002/prac.19923340609

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

Molecular Geometry and Excited Electronic States. XXIV. Theoretical Contribution to the S0and S1Molecular Structure and to the Sp← S0Electronic Spectral Behaviour of 1,4‐Distyryl Benzene an of its Doubly‐Charged IonsFor selected configurations of 1,4‐distyryl benzene and its doubly‐charged ions the completely‐optimized molecular geometries of the S0and S1states are presented. The structural peculiarities and differences are discussed. The Sp← S0electronic spectral data calculated on this basis are given and compared with available experim

ISSN:0941-1216    

DOI:10.1002/prac.19923340610

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

The Influence of Sodium Polyvinylsulfate on the Photodimerization of Acridizinium PerchlorateDuring the irradiation of aqueous solutions of acridizinium perchlorate (λexc= 405 nm) a photodimer of this compound is formed. The quantum yield of the reaction depends on the concentration of the acridizinium ion. In 10−4m solutions the quantum yield of dimerization is π = 0.0054 ± 0.0005. Addition of the anionic polyelectrolyte sodium polyvinylsulfate leads to a considerable increase of the quantum yield (up to π = 0.6) in dependence on the concentration of the polyion. A kinetic model is developed, including the electrostatic interaction of the acridizinium cation and the polyanion.The influence of diazonium cations as competitive agent is investigated and dic

ISSN:0941-1216    

DOI:10.1002/prac.19923340611

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY