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Ce(IV) as ceric ammonium nitrate can effectively catalyze ring opening of epoxides with halides under very mild conditions and easy procedure to give the corresponding β-chloro-and β-bromohydrins in excellent yields. The reactions occur with both substituted and unsubstituted quaternary ammonium halides and with high regio- and stereoselectivity. The reaction of optically active styrene oxide with chloride ion was found to be highly stereospecific and afforded the corresponding β-halohydrin in 96% ee. 相似文献
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Design and characterization of Dendrimer of MNPs as a novel,heterogeneous and reusable nanomagnetic organometallic catalyst for one‐pot synthesis of hydroxyl naphthalene‐1,4‐dione derivatives under solvent‐free conditions 下载免费PDF全文
A novel super acidic magnetic nanoparticle as catalyst was successfully synthesized. The preparation of this dendrimer sulfonic acid functionalized γ‐Fe2O3 magnetic core‐shell silica nanoparticles as a new recoverable and heterogeneous nanocatalyst was described. The new catalyst was characterized using various techniques such as scanning electron microscopy (SEM), energy dispersive spectrum (EDS), and thermo gravimetric synthesis (TGA). Moreover, we have examined the catalytic activity of the catalyst for one‐pot, efficient and facile synthesis of 2‐hydroxy‐1,4‐naphthoquinone derivatives via a three‐component condensation reaction of 2‐hydroxynaphthalene‐1,4‐dione, aromatic aldehydes and aniline derivatives. High yields of products, short reaction times, waste‐free, mild, ambient and solvent‐free reaction conditions are advantages of this protocol. Also, the catalyst can be easily recovered by an external magnetic and reused several times without significant loss of its catalytic activity. 相似文献
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Monomeric alkannin and shikonin (A/S) are potent pharmaceutical substances with a wide spectrum of biological activity and comprise the active ingredients for several pharmaceutical preparations. Therefore, the determination of the impurities, degradation products or byproducts in alkannin and shikonin samples is of great importance. Oligomeric alkannin and shikonin are formed during biosynthesis of these bioactive secondary metabolites in Boraginaceaous root plants, during tissue culture production of A/S, during alkaline hydrolysis of A/S esters and also thermal treatment of A/S. In the present study, a dimeric alkannin/shikonin compound was isolated by size exclusion chromatography from alkannin and shikonin commercial samples and its structure was determined by one- and two-dimensional NMR spectroscopy. The structure of the most abundant oligomeric species in these samples, a dimeric naphthoquinone, was established for the fi rst time, indicating that coupling of the side chain of one naphthoquinone unit with the aromatic ring of a second naphthoquinone leads to dimer formation. This type of coupling allows further oligomerization by leaving one isohexenyl side chain available at the second monomer unit. 相似文献
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Mono‐ and diamino‐derivatives of naphthazarin, 2‐methoxynaphthazarin, juglone and their methylethers were prepared by reaction with ammonia. The structure of the products was established by NMR studies. Some compounds were tested for cytotoxic activity. 相似文献
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Ferreira VF Jorqueira A Leal KZ Pimentel HR Seidl PR da Silva MN da Souza MC Pinto AV Wardell JL Wardell SM 《Magnetic resonance in chemistry : MRC》2006,44(4):481-490
The assignment of the diazo site in products of the reaction of p-toluenesulfonylhydrazine with beta-lapachone, 3,4-dihydro-2,2-dimethyl-2H-naphtho[1,2-b]pyran-5,6-dione, and other 1,2-naphthoquinones in methanol solution at room temperature has been accomplished using 1H,13C HMBC and 1H,15N HMBC NMR experiments. Only one diazo-naphthalenone product was isolated in yields ranging from 50-100% from each reaction. The site of diazo substitution of beta-lapachone and derivatives is the 1-position, in contrast to substitution at the 2-position in 4-MeO-1,2-naphthoquinone. Steric factors, rather than electronic factors, control the reaction site. Along with 2-diazo-1(2H)-naphthalenone, an additional product isolated from the reaction of p-toluenesulfonylhydrazide with 1,2-naphthoquinone was 2-diazo-4-hydroxy-1(2H)-naphthalenone. Confirmation of the formation of 6-diazo-2,2-dimethyl-2,3,4,6-tetrahydro-2H-benzo[h]cromen-5-one, obtained from beta-lapachone, was achieved using single crystal X-ray diffraction. 相似文献
6.
Jaécio Carlos Diniz Francisco Arnaldo Viana Odaci Fernandes Oliveira Maria Aparecida M. Maciel Maria da Conceição de Menezes Torres Raimundo Braz‐Filho Edilberto R. Silveira Otília Deusdênia L. Pessoa 《Magnetic resonance in chemistry : MRC》2009,47(2):190-193
From the roots of Cordia leucocephala (Boraginaceae), two new meroterpenoid naphthoquinones, 6‐[10‐(12,12‐dimethyl‐13α‐hydroxy‐16‐methenyl‐cyclohexyl)ethyl]‐1,4‐naphthalenedione (cordiaquinone L) and 5‐methyl‐6‐[10‐(12,12‐dimethyl‐13β‐hydroxy‐16‐methenyl‐cyclohexyl)methyl‐1,4‐naphthalenedione (cordiaquinone M) were isolated. Their structures were elucidated after detailed 1D and 2D NMR (COSY, HSQC, HMBC and NOESY) data analyses and comparison with literature data for analogous compounds. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
7.
Adushan Pillay Amanda L. Rousseau Manuel A. Fernandes Charles B. de Koning 《Tetrahedron》2012,68(35):7116-7121
Methodology for the synthesis of the benzo-fused acetal core of marticin is described in this paper. Condensation of readily available 1-(2-allyl-3,6-dimethoxyphenyl)ethanone with diethyl oxalate under Claisen condensation conditions furnished (Z)-ethyl 4-(2-allyl-3,6-dimethoxyphenyl)-2-hydroxy-4-oxobut-2-enoate. Treatment of this with LiAlH4 resulted in the formation of the diol, 1-(2-allyl-3,6-dimethoxyphenyl)-3,4-dihydroxybutan-1-one. Conversion of primary alcohol of the diol into the TBDMS ether followed by further reaction with LiAlH4 and exposure to Wacker oxidation conditions resulted in the formation of (3,6-dimethoxy-9-methyl-10,13-dioxatricyclo[7.3.1.02,7]trideca-2,4,6-trien-11-yl)methanol, the core of marticin. 相似文献
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The conjugate addition reactions of amines with 1,4‐naphthoquinone were catalyzed efficiently by molecular iodine under ultrasonic irradiation to afford 2‐amino‐1,4‐naphthoquinones in moderate to excellent yields. 相似文献