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971.
R. É. Valter É. A. Baumanis L. K. Stradynya É. É. Liepin'sh 《Chemistry of Heterocyclic Compounds》1981,17(4):375-378
The structures of 1-cyanoacetyl-2-alkylhydrazines and their ring isomers, viz., 1-alkyl-5-amino-3-pyrazolones, to which they are readily cyclized, were investigated by IR, UV, and PMR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 516–519, April, 1981. 相似文献
972.
13C and 31P chemical shift data for eight 2-methoxy-1,3,2-dioxaphosphorinanes are reported. Examination of pairs of geometrical isomers, which differ only in the orientation of the OMe substituent on PIII, have shown that both the 31P and the 13C signals of C4,6 atoms appear 3–4 ppm at higher field when the OMe is axial compared with the equatorial isomer. This observation can be associated with the 1–3 syn diaxial interaction between the phosphorus axial substituent and the axial hydrogens on C4,6 and should thus constitute, in the future, a supplementary tool for the structural analysis of this kind of compound. Important long range δ effects were observed both on 13C and especially on 31P chemical shifts. It is suggested that the high field δe effects could reflect a direct stereoelectronic interaction between the P atom and the cyclic C-5 atom. This interpretation is supported by a study of the 31P…13C coupling constants and their stereochemical dependence. 相似文献
973.
Abstract— Zinc porphin is photoreduced to zinc chlorin through an intermediate dihydroporphin (PH2 ) by ascorbic acid in ethanol containing 1% to 10% (v/v) piperidine. Under the same conditions zinc chlorin is more slowly photoreduced to zinc tetrahydroporphin. The reactions leading to chlorin are photosensitized by the product chlorin and so are autocatalytic in red light. Quantum yields for these reactions range up to 0.05.Other aliphatic amines catalyze these reactions, but at rates peculiar to the amine. The immediate product of reduction of zinc porphin, PH2 , is distinguished by an intense band at 437 nm; it reverts to porphin in the dark in the presence of oxygen or dehydroascorbic acid. Its conversion to chlorin is effected by light absorbed by porphin or chlorin, but not by light absorbed by PH2 itself. A suggested structure for PH2 , compatible with the observed reactions, has added hydrogens on one bridge carbon and one β-pyrrole carbon. The possibility of an analogy between these reactions and the biochemical conversion of protochlorophyll to chlorophyll is discussed. 相似文献
974.
Feijtel TC 《SAR and QSAR in environmental research》1995,3(3):237-245
Abstract Impending changes in EEC legislation have accelerated the need to define the principles and practical considerations of the use of QSARs in priority setting and risk assessment. It is important to delineate the limitations of this approach and to review whether and how this information should be used in the risk assessment. The value and limitations of QSARs for use in priority setting and risk assessment will not be discussed in detail since the European Chemical Industry Ecology and Toxicology Centre (ECETOC) has only recently established a Task Force to tackle this issue. The terms of reference of the Task Force are: (1) compare the predictions obtained with QSARs to measured data using ECETOC databases and other sources of data and comment on the validity and applicability of such QSARs; (2) identify and review software packages which are available for accessing and using appropriate QSARs; (3) identify those aspects of environmental distribution, fate and effects where the further development of QSARs is desirable and feasible; and (4) provide a scientific basis for ECETOC's contribution to the activities of the European Chemicals Bureau (ECB) in this area. In this short paper, only an initial and personal evaluation is made of when and where to use QSARs in the priority setting and risk assessment process within the regulatory framework. Some critical remarks and suggestions are provided to guide future developments and integration of QSARs in the risk assessment process. 相似文献
975.
L. Kh. Bikchurina R. Kh. Yumagulova L. M. Khalilov E. V. Vasil'eva G. V. Leplyanin 《Russian Chemical Bulletin》1990,39(6):1287-1291
The reaction of the acid chlorides of alkylenebisphosphonic acids with ethylene glycol and ethylene chlorohydrin gave ethylene glycol and -chloroethyl esters of alkylenebisphosphonic acids. The quaternization of these products leads to choline esters of alkylenebisphosphonic acids.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1424–1429, June, 1990. 相似文献
976.
Nanosecond flash photolysis has been carried out on benzophenone solutions in benzene and acetonitrile in presence of oxygen- and sulfur-containing reductants such as anisole, thioanisole, dibutyl sulfide and methyl 2-octyl ether. The quantum yield of ketyl formation is compared to previous results on the quantum yields of the final benzophenone disappearance. This comparison is also related to previous data on benzophenone reduction by nitrogen-containing reductants such as amines and amides and suggests a general mechanism for benzophenone photoreduction by heteroatom-containing donors. 相似文献
977.
Mesoionic thiazolones and selenazolones react with dimethyl acetylene dicarboxylate to give thiophenes or pyridones. We show that the reactivity of the mesoionic thiazolones towards dimethyl acetylene dicarboxylate may be explained by second order perturbation theory, limited to frontier orbitals. The influence of the temperature and of the nature of the substituants on the evolution of the primary cycloadduct can be explained by a competition between a retro Diels-Alder reaction giving a thiophene and a desulfurisation or a deselenurisation giving a pyridone. 相似文献
978.
The reactions of thionyl and sulphuryl chlorides on isoflavones have been found to give a number of new chloroisoflavones and isoflavanones, whose structures have been elucidated on the basis of their spectral analytical data. 相似文献
979.
Dimethyl α-bromo-o-benzenediacetate ( 1 ) condensed with hydrazine and acetylhydrazine to give respectively 1-carbomethoxy-2-amino-1,4-dihydro-3-(2H)isoquinolinone (2) and its N-acetyl derivative ( 9 ). Replacement of the bromine atom of 1 with the N-1-methylhydrazino ( 3 ) and the N-1-phenylhydrazino ( 5 ) groups occurred by allowing 1 to react respectively with methylhydrazine and phenylhydrazine. In the latter case alkylation by 1 at the N-2 also occurred which led to the formation of the 2-phenylaminoisoquinolinone ( 8 ). Derivatives 3 and 5 smoothly cyclized to the 1-earbomethoxy-5(H)-1,2,3,4-tetrahydro-2,3-benzodiazepin-4-ones 4 and 6 . A series of derivatives of 2 were also pharmacologically tested as antiinflammatory and CNS depressant agents. 相似文献
980.
The free NH3 molecule and the [Zn(NH3)4]2+ ion were studied by the kinematic coupling approach. The pure effects of this coupling were found to be small, and some modifications had to be introduced in order to get a reasonable force field. The force constants deduced for the skeletal vibrations are comparable with those of a quasi-exact force field. Calculated frequencies for [68Zn(NH3)4]2+ and [64Zn(ND3)4]2+ are reported in addition to those of [64Zn(NH3)4]2+. Mean amplitudes of vibration for [64Zn(NH3)4]2+ are given. 相似文献