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<P>A highly efficient and facile thermal multicomponent cascade reaction of readily available 4-oxo-4H-chromene-3-carbaldehydes with cyanoacetates or cyanoamides and anilines or aliphatic amines under solvent and catalyst-free conditions was developed for the synthesis of a range of polysubstituted 2-aminopyridine derivatives in good to excellent yield. This protocol proceeds via a cascade reaction of Knoevenagel condensation, nucleophilic addition, intramolecular Michael addition, and ring opening. As an application of this methodology, the antibacterial activities of some of the synthetic compounds were evaluated.</P>
Kellici, T.,Chatziathanasiadou, M.,Lee, M. S.,Sayyad, N.,Geromichalou, E.,Vrettos, E.,Tsiailanis, A.,Chi, S. W.,Geromichalos, G.,Mavromoustakos, T. Royal Society Chemistry 2017 Organic & biomolecular chemistry Vol.15 No.37
<P>An efficient synthetic approach to polysubstituted benzofurans is described, using 2-methoxyquinone as a benzofuran backbone. Nucleophilic addition of terminal alkynes to 2-methoxy-1,4-benzoquinone afforded the corresponding quinols containing an alkyne unit, which were converted to phenols via mild Zn-mediated reduction. After proper protection of the free phenolic OH, 5-endo-dig iodocyclization allowed facile access to a number of 3-iodobenzofurans. In addition, it was demonstrated for the first time that o-methoxyarylalkynes underwent intramolecular hydroalkoxylation under the influence of AgOTf furnishing the corresponding benzofurans.</P>
<P>A straightforward and efficient method for the synthesis of 1,2-diaryl-substituted enamines through the Cu-catalyzed electrophilic amination reaction of O-benzoyl hydroxylamines with vinyl-aluminum reagents generated in situ from the Ni-catalyzed hydroalumination of readily accessible internal aryl acetylenes is described. The amination is catalyzed by 1 mol% CuCl without any additive at ambient temperature to afford new versatile enamines in good yield (61-91%) with high selectivity (>98% E-enamine).</P>
<P>Here we report a straightforward cross-coupling method for the synthesis of non-natural glycoamino acids from alkyne-bearing monosaccharides and p-iodophenylalanine. Pd/Au-catalyzed Sonogashira coupling is tolerant to both O-and S-glycosides without any epimerization. In addition, no racemization of the amino acid was observed allowing direct access to the homogeneous glyco-conjugate in a single step. Notably, this Pd/Au catalytic system presents enhanced catalytic activity than conventional Pd/Cu and Pd-only platforms, and it further enables the convergent synthesis of glycodipeptides.</P>
<P>Growing evidence indicates intermediacy of singlet dioxygen (O-1(2)) in a variety of pathophysiological processes. O-1(2) has also found great utility of destructive actions for clinical and environmental applications. However, many details of the molecular mechanisms mediated by O-1(2) remain insufficiently understood. Efforts to elucidate the O-1(2) chemistry have been hampered by the lack of chemical tools capable of generation and detection of O-1(2). In this review, I summarize the recent advances in the development of the chemical tools of O-1(2). This article focuses on two topics. The first part introduces chemical methods for ground-state generation of O-1(2). Designs of the molecular carriers of O-1(2) are also explained. The second part discloses molecular probes of O-1(2). The probes are categorized into three groups, depending on signaling modalities: absorption-based probes, photoluminescent probes, and chemiluminescent probes. Focus is on the molecular design to maximize the signaling actions. Disadvantages of using the probes are also discussed to motivate the future research. I hope that this review will serve as helpful guidance to the exploitation and development of the chemical tools of O-1(2).</P>
<P>Treatment of the trifluoroacetyl enamides of dihydroisoquinolines 2 with diverse Grignard reagents afforded tertiary trifluoromethyl-carbinols 4 by facilitating the addition of tertiary carbinols to the beta-carbon of enamides 2. Based on the confirmed formation of vinylogous amides 3, the transformation likely proceeds via unique acyl group rearrangement to the beta-carbon of the enamide and subsequent nucleophilic addition of the Grignard reagent. Given the synthetic utility and novelty of this reaction, this work may open new avenues for the synthesis of pharmaceutically important tertiary trifluoromethylcarbinols on cyclic enamide systems.</P>