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951.
G. D. Kolomnikova T. O. Krylova I. V. Chernoglazova P. V. Petrovskii Yu. G. Gololobov 《Russian Chemical Bulletin》1993,42(7):1188-1190
In the presence of trifluoroacetic acid, ethyl 2-cyanoacrylate readily reacts with nucleophilic reagents, such as 2-chloro-1,3,2-benzodioxaphosphole, (EtO)3P, (EtO)2PCl, Ph2PCl, Ph3P, and thiourea. In these reactions the acid proton enters position 2 of the cyanoacrylate, whereas the nucleophilic component enters position 3, in accordance with the electron density distribution in the acrylate. In the absence of trifluoroacetic acid the above reagents, except 2-chloro-1,3,2-benzodioxaphosphole, cause ethyl 2-cyanoacrylate polymerization. The interaction of ethyl 2-cyanoacrylate with 2-chloro-1,3,2-benzodioxaphosphole and trifluoroacetic acid is the first example of a 2-cyanoacrylate taking part in the acid-initiated electrophilic conjugate addition of a weak nucleophile.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1245–1247, July, 1993. 相似文献
952.
本文研究了Cp_2ZrH_2与丙烯酸和Cp_2Zr(H)Cl与丙烯酸钠、巴豆酸钠的反应。产物由IR 1~H和~(13)CNMR、ESR谱、气相色谱以及化学方法分析鉴定。产物水解得到与底物相应的饱和酸.用~1H NMR方法考察了Cp_2ZrH_2与丙烯酸的反应过程,用IR方法考察了Cp_2Zr(H)Cl与丙烯酸钠的反应过程。实验结果表明,上面两种反应首先消除H_2或NaCl,形成锆氧健,然后碳碳双键还原生成二茂锆羧酸盐配合物,其中羧酸根离子与二茂锆桥式双齿配位。 相似文献
953.
P. Ramachandra T. Siva Rama Krishna Gautam R. Desiraju 《Journal of Chemical Sciences》1989,101(4):327-334
The compound 3-hydroxy-6-(4′-nitro)phenylazopyridine (1) was observed to incorporate several organic solvents of crystallisation, forming stable clathrates. These clathrates decompose
upon heating and the host material is chemically transformed. Single crystal X-ray diffraction studies on the ethanol clathrate
lead to a reasonable model for the host structure. But the guest molecules are severely disordered. Alternatively, the compound
forms twinned crystals. The chemically closely related compound2 does not form clathrates. 相似文献
954.
955.
脱羧氯雷他定 (DCL)是一种有效的非镇定性抗组织胺 ,对过敏性鼻炎 ,糖尿病、咳嗽、普通感冒、流行性感冒、关节痛及其它不适症状都有很好的疗效[1~2 ] 。它克服了氯雷他定、酮康唑、红霉素、伊曲康唑等易引发黑色素瘤、纤维肉瘤、胃刺激、肥胖症、心律失调、传导紊乱等症状的缺点。且它的使用剂量只有氯雷他定的十分之一 ,有很好的市场前景和实际应用价值。MarkW .Holladayetal[3] 在水溶液中由酸、碱催化得到了脱羧氯雷他定 ,但无具体操作和反应结果报道。A .K .GunnarAberg[1] 直接用KOH在绝对无水… 相似文献
956.
Knöevenagel-type reaction between diketene and aldehydes proceeded in the presence of Ti(O-i-Pr)4. This reaction proceeded via titanium enolate derived from Ti(O-i-Pr)4 and diketene. As for the stereoselectivity of the products, E-isomers were produced predominantly in the case of aromatic aldehydes. 相似文献
957.
DFT Study on the (S)-Proline-catalyzed Direct Aldol Reaction between Acetone and 4-Nitrobenzaldehyde
1 INTRODUCTION Aldol reaction, one of the most important C–C bond-formation reactions, is widely utilized in orga- nic synthesis[1]. Extensive efforts have been donated to the development of catalytic stereo-selective va- riants of this reaction[2]. However, the direct aldol reaction between unmodified carbonyles would be the most attractive synthetic alternative. Proline-catalyzed intermolecular direct aldol reac- tion between acetone and 4-nitrobenzaldehyde was first reported by List… 相似文献
958.
A. K. Galwey 《Journal of Thermal Analysis and Calorimetry》2006,86(1):267-286
This critical
survey argues that the theory, conventionally used to interpret kinetic data
measured for thermal reactions of initially solid reactants, is not always
suitable for elucidating reaction chemistry and mechanisms or for identifying
reactivity controls. Studies of solid-state decompositions published before
the 1960s usually portrayed the reaction rate as determined by Arrhenius type
models closely related to those formulated for homogeneous rate processes,
though scientific justifications for these parallels remained incompletely
established. Since the 1960s, when thermal analysis techniques were developed,
studies of solid-state decompositions contributed to establishment of the
new experimental techniques, but research interest became redirected towards
increasing the capabilities of automated equipment to collect, to store and
later to analyze rate changes for selected reactions. Subsequently, much less
attention has been directed towards chemical features of the rate processes
studied, which have included a range of reactants that is much more diverse
than the simple solid-state reactions with which early thermokinetic studies
were principally concerned. Moreover, the theory applied to these various
reactants does not recognize the possible complexities of behaviour that may
include mechanisms involving melting and/or concurrent/consecutive reactions,
etc. The situation that has arisen following, and attributable to, the eclipse
of solid-state decomposition studies by thermal analysis, is presented here
and the consequences critically discussed in a historical context. It is concluded
that methods currently used for kinetic and mechanistic investigations of
all types of thermal reactions indiscriminately considered by the same, but
inadequate theory, are unsatisfactory. Urgent and fundamental reappraisal
of the theoretical foundations of thermokinetic chemical studies is now necessary
and overdue.
While there are important, but hitherto unrecognized,
delusions in thermokinetic methods and theories, an alternative theoretical
explanation that accounts for many physical and chemical features of crystolysis
reactions has been proposed. However, this novel but general model for the
thermal behaviour and properties of solids has similarly remained ignored
by the thermoanalytical community. The objective of this article is to emphasize
the now pressing necessity for an open debate between these unreconciled opinions
of different groups of researchers. The ethos of science is that disagreement
between rival theories can be resolved by experiment and/or discussion, which
may also strengthen the foundations of the subject in the process. As pointed
out below, during recent years there has been no movement towards attempting
to resolve some fundamental differences of opinion in a field that lacks an
adequate theory. This should be unacceptable to all concerned. Here some criticisms
are made of specific features of the alternative reaction models available
with the stated intention of provoking a debate that might lead to identification
of the significant differences between the currently irreconciled views. This
could, of course, attract the displeasure of both sides, who will probably
criticise me severely. Because I intend to retire completely from this field
soon, it does not matter to me if I am considered to be ‘wrong’,
if it contributes to us all eventually agreeing to get the science ‘right’. 相似文献
959.
Spontaneous Nef reaction of primary and secondary 3-aryl-2-(diethoxyphosphoryl)-4-nitroalkanoic acids has been observed for the first time. The reaction provides a general and effective, highly diastereoselective synthesis of 3-(diethoxyphosphoryl)-1-hydroxysuccinimides and 2-(diethoxyphosphoryl)-4-oxoalkanoic acids. 相似文献
960.
Much improved catalytic carbon-carbon bond-forming reactions between aryl chlorides and Grignard reagents has been achieved using nickel(II) ion on nanoporous carbon. 相似文献