Novel polycyclic heterocycles. XIV. 1,2-Dihydro-4-(trifluoromethyl)-3H-8H-quino[1,8-ab][4,1]benzoxazepin-3-one and its derivatives

Procedures for the isolation of 1,2-dihydro-4-(trifluoromethyl)-3H,8H-quino[1,8-ab][4,1]-benzoxazepine, 3 , from reaction mixtures containing 3 as the minor component, and the isomer, 1,2-dihydro-11-(trifluoromethyl)-3H,7H-quino[8,1-cd][1,5]benzoxazepin-3-one, 2 , as the major component, are described. The reactivity of 3 toward hydroxylamine and aromatic aldehydes has been investigated and the preparation of derivatives with those reactants is described.     

NHC-Pd complex heterogenized on graphene oxide for cross-coupling reactions and supercapacitor applications

N-heterocyclic carbene (NHC)-palladium(II) complex (GO@NHC-Pd) was synthesized on graphene oxide (GO) support via a simple and cost-effective multistep approach. The spectroscopic, microscopic, thermal, and surface analyses of GO@NHC-Pd confirmed the successful formation of the catalyst. The investigation of catalytic activity showed that GO@NHC-Pd was very effective in Suzuki–Miyaura as well as Hiyama cross-coupling. Being heterogeneous in nature, GO@NHC-Pd was recovered after each reaction cycle easily and reused for up to nine and six cycles in Suzuki–Miyaura and Hiyama cross-coupling, respectively, without significant loss of activity. Further exploration of the supercapacitor performance of GO@NHC-Pd catalyst assembled in a two-electrode cell configuration shown a maximum attained capacitance of 105.26 F/g at a current density of 0.1 A/g with good cycling stability of 96.89% over 2,500 cycles.     

Preparation and surface charge studies of bio-magnetoelectrets of l-serine

This paper reports the study of surface charge characteristics of bio-magnetoelectrets of amino acid l-serine. Electrets were prepared under the combined effect of heat and magnetic field. Three different forming temperatures and five different magnetic fields were used for the study. The bio-magnetoelectrets prepared this way were observed to have a surface charge of the order of 10^?9 C. The decay of surface charge was studied continuously for 20 days and corresponding time constant was calculated. The comparative studies of surface charge characteristics were done by preparing bio-magnetoelectrets using homogeneous and inhomogeneous magnetic fields.     

Triazene-N-oxides as new type of fluorimetric reagents

Summary The fact that niobium gives orange fluorescence ( _ex ^max 570, _em ^max 540 nm) in both acid and alkali media with 3-(2-hydroxyphenyl)-1-phenyltriazene-N-oxide, has been exploited to develop a simple, sensitive and selective method for the determination of trace amounts of the metal in 50% ethanolic medium. Measurements are made at the pH range of 3.2–5.0. Fluorescence intensity attains the maximum value after 45 min of standing and remains almost unchanged after 24 h. Calibration graph maintains linearity from 50 ppb to 2.2 ppm of the metal. Forty cations and anions are without any effect on the fluorimetric determination of niobium(V). The method has been applied to the analysis of synthetic mixtures.     

Copper(II) catalyzed aromatization of tetrahydrocarbazole: An unprecedented protocol and its utility towards the synthesis of carbazole alkaloids

An efficient protocol for the aromatization of tetrahydrocarbazole is described by using catalytic copper(II) chloride dihydrate in DMSO. This newly established methodology has utilized towards the synthesis of naturally occurring carbazole alkaloids, namely 3-methylcarbazole, 3-formyl carbazole, glycozoline, glycozolicine and clauszoline-K. In addition, the protocol is generalized for the aromatization of N-substituted tetrahydrocarbazole, 1,2,3,4-tetrahydroquinoline, 1,2,3,4-tetrahydroisoquinoline and 1,2,3,4-tetrahydro β-carboline to give the corresponding heteroaromatic compounds from very good to excellent yield. Moreover, this method has been proven to be tolerant to a broad range of functional groups with excellent yields.     

Novel polycyclic heterocycles. VII. Synthesis of tetracyclic ketones and derivatives from tricyclic 5,11-dihydrodibenz[b,e][1,4] oxazepines

Michael addition of 5,11-dihydrodibenz[b,e][1,4]oxazepines to acrylonitrile gave 5,11-di-hydrodibenz[b,e][1,4]oxazepine-5-propionitriles, which were converted to the corresponding methyl 5-propionates. Mild alkaline hydrolysis of these esters furnished the key intermediates, the 5,11-dihydrodibenz[b,e] [1,4]oxazepine-5-propionic acids. In the preferred procedure, these propionic acids were cyclized to the tetracyclic ketones in yields of 60-90%, by the action of one equivalent of trifluoroacetic anhydride in benzene. When ring C was involved in cylcization, 1,2-dihydro-3H,7H-quino[8,1-cd][1,5]benzoxazepin-3-ones were obtained, and when ring A was involved, 1,2-dihydro-3H,8H-quino[1,8-ab] [4,1]benzoxazepin-3-ones were formed. With 1c , both modes of cyclization were observed. In an alternative procedure that gave lower yields, the propionic acids were first converted to the corresponding acid chlorides, and these were cyclized by means of anhydrous stannic chloride; as anticipated, the products by this method were identical with those obtained via the trifluoroacetic anhydride method. Several reactions of these tetra-cylcic ketones, e.g., their ease of oxime formation, and dehydrogenation to the α,β-unsaturated ketones, are described. The α,β-unsaturated ketones do not form oximes. The structures assigned to the ketones are based on interpretations of their pmr, uv, and ir spectra. These assignments were confirmed by an X-ray analysis of a single crystal of one representative ketone, 2b ; the X-ray study was also useful in indicating the thermodynamically preferred conformation of 2b . The structures of all the other compounds followed from similar spectral interpretations. The mass spectra of a few compounds are also discussed.     

A comparative study of structural, acidic and hydrophilic properties of Sn-BEA with Ti-BEA using periodic density functional theory

Periodic density functional theory has been employed to characterize the differences in the structural, Lewis acidic and hydrophilic properties of Sn-BEA and Ti-BEA. We show that the incorporation of Sn increases the Lewis acidity of BEA compared to the incorporation of Ti. Hence, the present work gives insight into the role of Sn in increasing the efficiency of the oxidation reactions. The results also justify that the percentage of Sn substituted in BEA is less than Ti. The structural analysis shows that the first coordination shell of Sn is larger than that of Ti. However, the second coordination of both sites remains the same. The water adsorption properties of these substituted zeolites are quantified. Moreover, we explain the higher Lewis acidity of Sn than the Ti site on the basis of the Fukui functions and charge population analysis.     

Triazene-N-oxides as new type of fluorimetric reagents. part i. trace determination of zirconium at the nanogram level

Summary Triazene-N-oxides are being reported for the first time as a new type of metallofluorescers. Among eleven triazene-N-oxides studied, 3-(2-hydroxyphenyl)-l-phenyl triazene-N-oxide(R₁₁) gives fluorescence with Zr, Hf, Nb(V) and Ta(V). A method has been developed for trace determination of Zr with R₁₁, excitation and emission maxima of the system being 435 nm and 570 nm respectively.In the pH range between 1.65 and 1.95 the fluorescence intensity of Zr-R₁₁ system is linear over the range 5 ppb to 1.5 ppm of zirconium. Some thirty ions show no interference or can be removed by the use of masking agents. Only Hf, W and Mo cause interference. The method is simple and very rapid.

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Triazen-N-Oxide als neuartige fluorimetrische Reagenzien. I. Bestimmung von Zirkon im Nanogrammbereich

Zusammenfassung Triazen-N-oxide wurden erstmalig als fluoreszenzanregende Reagenzien für Metalle vorgeschlagen. 3-(2-Hydroxyphenyl)-1-phenyltriazen-N-oxid (R₁₁) gibt mit Zr, Hf, Nb(V) and Ta(V) Fluoreszenz. Ein Verfahren für die Bestimmung von Zr-Spuren mit R₁₁ durch Anregung bei 435 nm und Messung beim Fluoreszenz-Maximum (570 nm) wurde ausgearbeitet. Im pH-Bereich 1,65–1,95 ist die Fluoreszenz-Intensität von Zr-R₁₁ zwischen 5 ppb und 1,5 ppm Zr linear. Einige dreißig Ionen stören nicht bzw. können maskiert werden. Nur Hf, Mo und W stören.

     

Ultra-performance liquid chromatographic determination of manufacturing intermediates and subsidiary colors in D&C Red No. 34 and its lakes

An ultra-performance liquid chromatography (UPLC) method was developed to determine the manufacturing intermediates and subsidiary colors in the monosulfo monoazo color additive D&C Red No. 34 and its lakes. This method is currently used for batch certification of the color additives by the U.S. Food and Drug Administration to ensure that each lot meets published specifications for coloring drugs and cosmetics. The new UPLC method has replaced an HPLC method for determining the intermediates and a TLC method for determining the subsidiary colors. The intermediates are 2-amino-1-naphthalenesulfonic acid (Tobias acid) and 3-hydroxy-2-naphthalenecarboxylic acid (3-hydroxy-2-naphthoic acid). Subsidiary colors are positional isomers of the major dye component or related compounds containing lower numbers of substituent groups. The analytes are identified by comparison of their UPLC retention times and UV or visible absorption spectra with those of standards. Validation studies showed that peak area calibrations for the analytes were generally linear (R > 0.999), and recoveries were 98-103%. The LODs were 0.002-0.02%, and the RSDs at the specification levels were 0.7-2.2%. Survey analyses of 12 samples of certified D&C Red No. 34 straight colors and lakes from six domestic and foreign manufacturers yielded results for the intermediates by UPLC and HPLC that were consistent within experimental error. The UPLC analyses yielded results for the subsidiary colors that were consistently lower than results previously obtained by TLC, which we attribute to limitations of the TLC method. The new UPLC method provides sharper peaks, better peak separation, and faster analysis times than the formerly used HPLC method and is more accurate, much faster, and much less labor-intensive than the formerly used TLC method.