摘要:

Formylierungsprodukte von Thioamiden. IV. Reaktionen von 3‐Dialkylamino‐und 3‐Hydroxythioacrylamiden mit Aminen – Synthese von 3‐Aminothioacrylamiden, 5‐Aminopyrazolen und 3‐Aminoisothiazoliumsalzen3‐Hydroxythioacrylsäureamide (5) oder 3‐Dialkylaminothioacrylsäureamide (4) bzw. deren Salze (3) werden von Aminen oder Hydrazinen leicht in 3‐Position unter Substitution angegriffen, wobei 3‐Aminothioacrylsäureamide (6) gebildet werden. Über die Zwischenstufe der6sind in Abhängigkeit vom Substituenten in 3‐Position entweder durch Oxydation 5‐Aminoisothiazoliumsalze (7) oder durch intramolekularen nucleophilen Angriff am Kohlenstoffatom 1

ISSN:0021-8383    

DOI:10.1002/prac.19833250502

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

1H‐N.M.R. Spectroscopic Investigations on Stereochemistry of Substituted ButadienesThe butadienes1–6, obtained by Knoevenagel condensation of furfuryliden, 5‐bromofurfuryliden, and benzylidenaceton with malononitril and ethyl cyanoacetat respectively, have been investigated1H‐n.m.r. spectroscopically. Structure and configuration of the isomers could be determined with the help of deuteration experiments, anisotropy effects, and Eu(fod)3shift reagents measu

ISSN:0021-8383    

DOI:10.1002/prac.19833250503

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

On the Pyrolysis of Pent‐1‐ene‐4,4,5,5,5‐d5The distribution of deuterium in the main products of thermal decomposition of pent‐1‐ene‐4,4,5,5,5‐d5at 550 to 650°C was studied and interpreted. The results include conclusions on kinetic isotope effects, on relative reactivities of different C‐H‐bonds, on the proportion of terminal and nonterminal addition of methyl radicals, and on the importance of a radical isomerisation reaction. It was shown that the molecular decomposition (Retro‐En‐Reaction) cannot successfully compete with the radical way in the temp

ISSN:0021-8383    

DOI:10.1002/prac.19833250504

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

AbstractO‐ and N‐Alkylsubstituted 2‐(2′‐Hydroxyphenyl)‐benzimidazoles and ‐1,3,4‐Oxadiazoles as Complexing and Extracting Agents for Copper‐II‐Ions2‐(2′‐Alkoxyphenyl)‐benzimidazoles1, 1‐alkyl‐2‐(2′‐hydroxyphenyl)‐benzimidazoles2, 2‐(2′hydroxy‐4′‐alkoxyphenyl)‐benzimidazoles3, 2‐(2′,4′‐dialkoxyphenyl)‐benzimidazoles4and 1‐alkyl‐2‐(2′‐hydroxy‐5′‐nitrophenyl)‐benzimidazoles7are synthesized by condensation of 2‐hydroxybenzoic acid derivatives and o‐phenylenediamine or its derivatives. Alkyl chains C4, C8or C12are introduced by alkylation before or after the ring closure in order to increase the solubility of the reagent in toluene or n‐octane. Furthermore the extraction properties of the benzimidazoles are investigated. Also some new anal

ISSN:0021-8383    

DOI:10.1002/prac.19833250505

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

Three Component Reactions. XVI. Halogenation of Alk‐1‐enes in the Presence of Ethylene Oxide und Propylene OxideThe products of the chlorination of alk‐1‐enes in the presence of ethylene oxide and propylene oxide were investigated in relation to products of the chlorination in the presence of corresponding chloroalcohols4and5. Isomers dominating in the Markovnikov orientation were found in all cases. Two of the three pairs of diastereomeric bischloropropylethers expected for the chlorination of propene in the presence of propylene oxide were identified by capillar GLC and13C n.m.r. spect

ISSN:0021-8383    

DOI:10.1002/prac.19833250506

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

Pyrylium Compounds. XVIII. 2‐Alkoxy‐2H‐pyrans from Tetra‐ and Pentasubstituted Pyrylium SaltsAlkali alkoxides add regioselectively to 2,3,4,6‐tetrasubstituted pyrylium salts7(R' H), affording high yields of colourless crystalline 2‐alkoxy‐2H‐pyrans9. The latte are also formed simply on refluxing7in the corresponding alcohol with triethylamine as proton acceptor. 3,5‐Dialkylsubstituted 2,4,6‐triarylpyrylium salts react analogously. The 2H‐pyran structure of the adducts obtained follows from their n.m.r., i.r., u.v. and mass spectra as well as from their reaction with tetracyanoethylene to cycloadducts of type10. Acids regenerate from9the original pyrylium cations, whereas reaction of9with nitromethane or ethyl cyanoacetate provides benzene derivatives. ‐‐ The novel starting pyrylium salts7b‐‐oare characterized by u.v./vis data and by transformation into the co

ISSN:0021-8383    

DOI:10.1002/prac.19833250507

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

On the Conformational Behaviour of Substituted Phenylbenzoates ‐ Molecular and Crystal Structure of the Nematogenic Compound 4′‐(ß‐Cyanoethyl)‐phenyl‐4‐n‐pentoxybenzoateThe title compound crystallizes in the monoclinic space group P21/n with a = 1567.6(2) pm, b = 915.5(1) pm, c = 1459.1(1) pm, β = 115.30(1)°, and four molecules per unit cell. The structure has been solved by direct methods and refined to R = 0.104. The molecules adopt a markedly stretched form and show a parallel arrangement of their long axes in the crystal lattice. The molecular and crystal structure is discussed in relation to the mesomorphic behaviour of the compound.A theoretical conformational analysis has been performed for the isolated phenylbenzoate molecule using the EPEN/2 method, its results are compared with the experimental torsion angles in a series of substitut

ISSN:0021-8383    

DOI:10.1002/prac.19833250508

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

Photoinduced Decomposition of Arene Diazonium Salts by Metal OxalatesArene diazonium salts were decomposed by the irradiation of K3[Fe(oX)3] and K3[Co(ox)3]. The dediazonation is caused by electron transfer reactions between ·CO‐2and in the case of the former complex also by [Fe(ox)2]2‐‐species. As intermediates aryl radicals were found by spin trapping with nitroso durene. The dediazonation quantum yields (0,15‐‐1,21) depend on the reduction potentials of the salts and on the oxalate concentration. By electron acceptor substituted diazonium salts the values are the same as those of the K3[Fe(ox)3]‐actinometer. In the case of p‐dialkylaminobenzene diazonium salt‐types an electron transfer takes places with ·CO‐2only whereas the reaction with [Fe(ox)2]2−is neglectable. A Hammett‐correlation for the electron transfer of Fe(II)‐species with a ϱ‐value of 1.7 was found. The investigated systems are efficient initiator

ISSN:0021-8383    

DOI:10.1002/prac.19833250509

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

Chemical Synthesis of the Pentadecadeoxyribonucleotide d(TTCTTCTACACACCC) by Improved Triester ApproachThe chemical synthesis of the pentadecanucleotide d(TTCTTCTACACACCC) by improved triester approach in solution with TPS/1‐Methylimidazole as condensation agent is reported. Almost all condensation were complete within 5‐‐10 minutes giving yields over 80%. All intermediate triester blocks showed purity degrees of higher than 90% after purification by simple silicagel chromatography. After deblocking the pentadecanucleotide was purified by DEAE‐cellulose 52 chromatography and desalted, then showing 100% purity as seen by 20% polyacrylamide gel electrophoresis of the 5′‐32P labeled oligonucleotide. The sequence of the synthetic oligomer was determined and confirmed by using the two‐dimensional mobility shift method. The pentadecanucleotide was used as hybridisation probe for cloned human

ISSN:0021-8383    

DOI:10.1002/prac.19833250510

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

Theoretical Investigations on the Decomposition Equilibrium of Urea in Gaseous State and Aqueous SolutionThere is empirical evidence that among the two possible decomposition equilibria of urea in the gaseous and aqueous states the desammonation process prevails. In the present work the thermodynamic and kinetic conditions of desammonation and dehydration based on intramolecular mechanisms were examined by means of quantum chemical methods. The application of MNDO method yields correct structural data, dipole moments and ionisation potentials; the solvation is taken into account using NDDO based solvation and reaction field models. Maximum deviations concerning enthalpies of formation in π‐electron rich compounds reach up to 40kJ/mole. A detailed examination of the energy hyperfaces reveals that the dehydration is kinetically hindered by a significantly high activation barrier. This situation is not essentially altered by taking into account nonspecific solvent effects in aqueous soluti

ISSN:0021-8383    

DOI:10.1002/prac.19833250511

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY