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Alcindo A. Dos Santos Renan S. Ferrarini Jefferson L. Princival João V. Comasseto 《Tetrahedron letters》2006,47(50):8933-8935
A masked lithium homoenolate, generated by tellurium/lithium exchange, was reacted with epoxides. The lithium compound was also converted into other organometallics such as Grignard, and cuprates and the reactivity of those organometallics with epoxides was evaluated. The same building block was employed in the synthesis of (+/−)-frontalin. 相似文献
4.
The twisting power of chiral probes in nematics is interpreted in terms of a shape model, in which the surface elements of the solute molecules tend to align with the local director. The theoretical treatment is based on a previous approach, suitable for relating order parameters in nematics to molecular shape, and leads to the definition of a molecular pseudo-tensor whose orientational average determines the pitch and handedness of the helical macrostructures. Results of numerical calculations performed for distorted biphenyl and binaphthyl molecules are in agreement with the experimental results. 相似文献
5.
Stefano Vecchio Alessia Catalani Vanessa Rossi Mauro Tomassetti 《Thermochimica Acta》2004,420(1-2):99-104
The thermal behaviour of acetanilide (Ac) and two of its analogues, namely the para-ethoxyacetanilide (p-Eto Ac) and the para-bromoacetanilide (p-Br Ac), which are used as analgesics in the pharmaceutical industry was studied with a simultaneous TG/DSC unit. The examined analgesics showed two endothermic DSC peaks due to melting and vaporization. By combining the experimental TG data with the corresponding reference vapour pressure data obtained with the Antoine equation the plot of P versus v was derived. From the slope of this equation the constant k-value was determined for Ac. Then, using the same k-value the vapour pressures of p-Eto Ac and p-Br Ac were determined in the same temperature range. The vaporization enthalpies for all the studied compounds were obtained from different methods and a very good agreement was found. Vaporization follows a zero-order kinetics. The activation energy of vaporization (Evap) was calculated from the dynamic TG experiments, using the Arrhenius equation. 相似文献
6.
S. Carboni A. Da Settimo P. L. Ferrarini P. L. Ciantelli 《Journal of heterocyclic chemistry》1970,7(5):1037-1043
Several tetrazole derivatives have been prepared from 7-amino-2-hydroxy-3-phenyl-1,8-naphthyridine (Id). Evidence is presented to demonstrate that the tetrazole ring structure is the dominant species in the solid state and in alkaline solution while the open-chain azido form dominates in acidic solution. In addition it has been shown that the presence of a phenyl group in a position adjacent to the tetrazole nucleus apparently stabilizes the tetrazole ring. 相似文献
7.
Specific programming of automated HPLC systems allows total on-line qualification, validation and stability monitoring using the concept of deferred standards. Setting up such a process for routine analyses in an automated HPLC system requires specific autosampler programming as well as specific monitoring software. With an autosampler, a double injection procedure is programmed, the first introducing the sample, and the second, a few minutes deferred, the deferred control standard. Two additional compounds are therefore added to the sample before and during the chromatographic process: the intemal standard for sample quantification and the deferred standard for system control. Specific methodologies are described of how to obtain classical quantitative analysis information as well as system qualification validation stability information. Experiments were performed to develop specified methodologies to monitor the quality of quantitative analysis during the life of the column by using the deferred standard concept to probe the effects of column ageing on separation characteristics. 相似文献
8.
Zanoni G Porta A Meriggi A Franzini M Vidari G 《The Journal of organic chemistry》2002,67(17):6064-6069
Regioconvergent synthesis of the key lactone 1 from an equimolar mixture of the two olefins 4 and 5 was achieved by unique Pd(II) chemistry. The synthetic versatility of lactone 1 has been demonstrated in the synthesis of iridoids and of the endo-Corey lactone 2, which is a key intermediate for the F(2)-isoprostane synthesis. Upon exposure of the sodium salts of 4 and 5 to a catalytic amount of Pd(OAc)(2) under oxygen, in the presence of AcOH, an isomeric lactone 12 was obtained in addition to the title compound 1. The Pd(II) lactonization was optimized by fine-tuning all the factors participating in the catalytic cycle: solvent, oxidant, co-oxidant, and Pd(II) source. The Hosokawa's heterobimetallic couple emerged as the catalyst of choice. With a Cu(II)-Pd(II) couple, the redox process was transferred to copper, and the formal oxidation state of palladium remained constant during the reaction. By virtue of this new methodology, lactone 1 was obtained in a rewarding 60% yield, along with isomeric lactone 12 in 30% yield. A detailed mechanistic study was carried out in order to elucidate the formation of lactones 1 and 12. Lactone 1 was formed from either olefin 8 or olefin 10; on the other hand, lactone 12 was formed exclusively from olefin 10. An intramolecular 1,2-acyloxypalladiation was invoked for the transformation of 8 into 1, whereas the pi-allyl complexes 13 and 11 were involved in the transformation of olefin 10 into 12 and 1, respectively. 相似文献
9.
Pier Luigi Ferrarini Claudio Mori Muwaffag Badawneh Clementina Manera Adriano Martinelli Federico Romagnoli Giuseppe Saccomanni Mauro Miceli 《Journal of heterocyclic chemistry》1997,34(5):1501-1510
Several 1,8-naphthyridine derivatives have been diazotizated to obtain the corresponding hydroxy derivatives or mixture of hydroxy and hydroxy nitro derivatives. The respective amounts of hydroxy and hydroxy nitro derivatives depends on the nature of the substituents, on their position on the naphthyridine nucleus, on the amount of sodium nitrite and on the reaction temperature. A study of the electronic density of some molecules suggests a possible explanation of the effects induced by the nature of the substituents and of their position. Some of the compounds were tested for their ability to inhibit human platelet aggregation in vitro induced by arachidonic acid. Only compound 26 showed interesting antiplatelet activity. 相似文献
10.
Bacchi Alessia Pelizzi Giancarlo Minardi Giovannina Pistuddi Angelo M. Solinas Costantino Chelucci Giorgio 《Transition Metal Chemistry》2002,27(3):274-278
Metal complexes of general formula M(L)X2 and M(L)X3 [L = (4S,5S)-2,2-dimethyl-4,5-bis{6-[(4,5-dihydro-4-(S)-(1-methylethyl)oxazol-2-yl)pyridin-2-yl]}-1,3-dioxolane] were obtained by reacting, respectively, CoII, CuII, NiII, and ZnII nitrate salts and the RhIII chloride salt, with a chiral C2-symmetric bis(oxazolinylpyridinyl)dioxolane (L) ligand, in MeOH/CHCl3 solution. A single crystal X-ray analysis was carried out on [Ni(L)(OH2)2](NO3)2 · 2H2O and the molecular structure of L was also determined. In the free ligand the two symmetric arms are essentially planar and oriented nearly perpendicular to the dioxolane average plane. In the Ni complex one seven-membered and two five-membered chelation rings are formed. The metal atom also lies on the C2 axis, and two symmetry-related water molecules complete the octahedral coordination environment. Both compounds crystallize in chiral space groups; the ligand crystallizes in orthorhombic system, space group C 2 2 21, Z = 4; the nickel complex crystallizes in tetragonal system, space group P 43 21 2, Z = 4. 相似文献