摘要:

AbstractIn contrast to previous hypotheses that there are a few primary odors, recent results show the existence of an extremely large number of receptors each capable of recognizing a small number of odorants. Although in principle enantiomers have different odors, in many cases the size of the difference is small or even zero. Minor structural change often has a major effect on the odor perceived. Detailed results of structure‐odor relationship have been obtained with several classes of odorants. Most investigated are the classes of fatty aldehydes, degraded carotenoids, sandalwood odorants, ambergris and musk compounds. Various rules and correlations have been established. Despite numerous excellent studies during the last 30 years the area of structure‐odor relationship remains rather confus

ISSN:0941-1216    

DOI:10.1002/prac.19943360202

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

Quinones. XIII. Synthesis of 4,5,9,10‐Tetrahydropyrene‐2,7‐dione and Attempted Preparation of Pyrene‐2,7‐dioneThe titel quinones7and9are of interest as electron acceptors for organic conductors. The synthesis of their conjugate hydroquinones6and8via the metacyclophane derivative3is described. The tetrahydropyrene‐2,7‐dione7– obtained by oxidation of6– possesses only a limited stability, whereas pyrene‐2,7‐dion (9) proved to un

ISSN:0941-1216    

DOI:10.1002/prac.19943360203

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

Synthesis of New N‐Aroylisothiazole‐2‐imines and N‐Aroylaminoisothiazolium Salts by Cyclisation of Thiocyanato‐substituted HydrazonesThe synthesis of new N‐aroylisothiazole‐2‐imines (4g‐n) as well as the corresponding acceptor‐substituted 2‐amino‐isothiazolium salts (6f‐n) by cyclocondensation of thiocyanatovinylaldehyde hydrazones (3) is reported. The structure of these N‐imines was proved by spectroscopic methods. The alternative cyclization route to 1,2,3‐thiadiazines (8) is not observed. The hydrazones (3a‐e) could not be cyclized to N‐imines, only sulfides (5a‐c) were obtained. The reaction of 2‐thiocyanatomethylen‐cycloheptan‐2‐one (9) with benzhydrazides gave the same ring closure to the salts (10a,b). The structure of the N‐imine11bhas been confir

ISSN:0941-1216    

DOI:10.1002/prac.19943360204

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

Synthesis of 2‐Alkoxy Substituted Oligo‐ and Poly(1,4‐phenyleneethylene)s and 2‐Arylbenzo[b]furanes by Applying the Siegrist ReactionAlkylation of 2‐hydroxy‐4‐methylbenzaldehyde (1) yields the 2‐alkoxy‐4‐methylbenzaldehydes (2a‐l) which can be easily transformed to the Schiff bases3a‐l. Theintermolecularself‐condensation in a strongly alkaline medium leads to the oligo‐ and poly(1,4‐phenyleneethenylene)s (4a‐i) with an outstanding regular constitution and overall (E)‐configuration. The terminal N‐arylamino group can be cleaved by hydrolysis generating the compounds5a‐i. Anintramolecularcondensation forming the benzo[b]furanes6j,kis observed for3j,k– due to the activated OCH2group in 2‐position. Finally, both the 4‐CH3as well as the 2‐OCH2group take part in the reaction of3l. The twofold Schiff base3m, obt

ISSN:0941-1216    

DOI:10.1002/prac.19943360205

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

Heterocyclic β‐Enamino Esters. 57. Studies on the N‐Glycosylation of Heterocondensed UracilsN‐Glycosylations of various heterocondensed uracils of the general type4are described. The thieno[2,3‐d]pyrimidines (9a‐e) afford with 1‐O‐acetyl‐2,3,5‐tri‐O‐benzoyl‐D‐ribofuranose (7) the corresponding 1‐ribosides (10a‐e) in a modified Hilbert‐Johnson‐Birkofer synthesis; from these10awas smoothly saponified to give the free riboside11a. – In a more generally applicable stereospecific sodium salt glycosylation procedure employing α‐acetobromglucose, the 1‐glucosides12–16and with β‐(trimethylsilyl)ethoxymethyl chloride (SEM‐Cl) a variation of acyclonucleosides17–22have been obtained. The s

ISSN:0941-1216    

DOI:10.1002/prac.19943360206

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

On the Anodic Behaviour of Magnesium in Non Aqueous Elektrolytic SolutionsThe paper presents results of electrochemical studies on systems of the compositionmagnesium/non aqueous electrolyte. By means of curentless stability‐ and polarization measurements as well as impedance characteristics the behaviour of the system Mg/n‐C4H9OH/0,2M NaClO4is described in particular. Cyclic voltammograms and impedance spectra demonstrate a passivating layer on the metal surface prior to the first polarization starts. It determines the anodic behaviour. Deviations in the Bode diagram at high frequencies can be traced back to spurious capacities within the measuring c

ISSN:0941-1216    

DOI:10.1002/prac.19943360207

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

N‐Functionalized Cyclopentadienide Anions; Chloronium‐ and Bromonium‐Cyclopentadienides2,3‐Dicyano‐1,4‐diethoxycarbonylcyclopentadienide anion (3) is N‐functionalized by nitration, nitrosation, azo coupling or diazo‐group transfer. Phenylbromonium‐ and phenyl‐chloronium‐cyclopentadienes14and15are synthesized by photolysis of the diazo compound13in the ap

ISSN:0941-1216    

DOI:10.1002/prac.19943360208

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

Photometric Indication of the Determination of Water by the Karl Fischer MethodPhotometry can be used instead of voltammetry for the indication of the water determination by the Karl Fischer method. Titration photometers using glass fibers (Metrohm) or photodiodes (Mettler) ensure an analytical performance equal to that of polarization methods. Standard endpoint titrators can be successfully used with the photometric signal. Both volumetric and coulometric titration can be photometrically indicated. The principle is applicable to colored and moderately turbid solutions as well.

ISSN:0941-1216    

DOI:10.1002/prac.19943360209

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

Liquid Phase Oxidation of 1,3‐DioxolanesThe oxidation rate and the kind of oxidation products in the oxidation reactions of the 1,3‐dioxolanes (1ato1f) with molecular oxygen in liquid phase were investigated. The 2‐methyl‐substituted 1,3‐dioxolane (1b) has a lower, the 4‐methyl‐substituted 1,3‐dioxolane (1d) has a higher oxidation rate than the non‐substituted 1,3‐dioxolane (1a). The 2,2‐disubstituted 1,3‐dioxolanes show no oxidation but a hydrolytic reaction. The main‐products of the liquid‐phase oxidation of the 1,3‐dioxolanes1a,1b,1dand1eare the glycol‐carbonic acid‐monoesters8and the 2‐oxo‐1,3‐dioxolanes6. Their formation is proved by gaschromatography, GC/MS

ISSN:0941-1216    

DOI:10.1002/prac.19943360210

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractThe reaction of ethyl N‐(6‐ethoxycarbonyl‐2‐methyl‐thiothieno[2,3‐d]pyrimidin‐5‐yl)formimidate (1) with methyl‐hydrazine, N,N′‐dimethyl‐ and N,N′‐diphenylhydrazines separately in refluxing ethanol resulted in hydrolysis of formimidate group to give ethyl 5‐amino‐2‐methylthiothieno[2,3‐d] pyrimidine‐6‐carboxylate (2). The reaction on1with methyl‐hydrazine without solvent afforded ethyl 5‐amino‐2‐(1‐methyl‐hydrazino)thieno[2,3‐d]pyrimidine‐6‐carboxylate (3), which underwent hydrazone formation with p‐nitrobenzaldehyde to give4. Treatment of1with N,N‐dimethylhydrazine afforded a mixture of 3‐dimethylamino‐7‐methylthiothieno[2,3‐d:4,5‐d']dipyrimidin‐4(3H)‐one (5) and2. Displacement of methylthio group in5with morpholine, piperidine and 4‐methylpiperazine gave the corresponding 7‐substituted derivatives6a‐c. The reaction of1with para‐substituted phenylhydrazines resulted in the formation of 3‐(p

ISSN:0941-1216    

DOI:10.1002/prac.19943360211

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY