Imino Diels–Alder adducts. XII. Two pyrano[3,2‐c]quinolines

The crystal structures of pyrano­quinolines 9‐fluoro‐5‐phenyl‐3,4,4a,5,6,10b‐hexa­hydro‐2H‐pyrano[3,2‐c]quinoline, C₁₈H₁₈FNO, and 9‐methyl‐5‐phenyl‐3,4,4a,5,6,10b‐hexa­hydro‐2H‐pyrano­[3,2‐c]quinoline, C₁₉H₂₁NO, are isomorphous. In both structures, the pyran ring is exo to the six‐membered N‐heterocyclic ring formed in the cyclo­addition step. The torsion angles across the phenyl linkage for the two structures are −91.2 (1) and −88.3 (2)°. The striking feature in both crystal packings is that they do not contain the expected conventional hydrogen bonds, in spite of the presence of good hydrogen‐bonding functionalities. Possible C—H⋯π inter­actions are, however, observed.     

Composition and spectral studies of polyaniline salts

Five different polyaniline salts have been prepared by chemical polymerization of aniline in aqueous solution of different acids. The polyaniline base was obtained from the corresponding polyaniline salt by dedoping using aqueous ammonium hydroxide solution. Electron paramagnetic, electronic absorption, infrared spectral and conductivity measurements have been performed on the polyaniline salts and polyaniline bases. This composition and the extent of dopant in polyaniline salt systems have been determined. There is no definite correlation between the conductivity and the stoichiometric ratio between the polyaniline base and the acid, and also the spin concentration.     

Sc(OTf)3-catalyzed alkylation of indoles with propargyl alcohols: an expeditious synthesis of 3-substituted indoles

Indoles undergo smooth alkylation with propargylic alcohols in the presence of 10 mol % of scandium triflate under mild conditions to produce 3-propargylated indoles in excellent yields with high selectivity.     

Preparation,Solid‐state Characteristics,and Catalytic Properties of Promoted Vanadium Phosphate Materials

The syntheses of transition metal promoted (M = Co, Cr, Fe, Mo) supported vanadium phosphate (VPO) catalysts (TiO₂ (anatase), γ‐Al₂O₃) and their characterization by N₂‐adsorption, X‐ray diffractometry (XRD), FTIR‐spectroscopy and determination of V‐valence state is reported. The catalytic properties were checked in the heterogeneous catalytic ammoxidation of 2, 6‐dichlorotoluene to the corresponding nitrile. The catalyst samples were prepared by synthesis of the precursor compound VOHPO₄ · 0.5 H₂O, impregnation using various metal salt solutions and mixing with the support materials. The characterization revealed increased surface areas for all the promoted samples in comparison to the basic materials. XRD showed the formation of (VO)₂P₂O₇ after calcinations as well as patterns of support materials (anatase, γ‐Al₂O₃). The formation of crystalline proportions of mixed oxides were not observed. The catalytic ammoxidation runs revealed a significant effect of the promoter metals on the catalytic properties by an increase of yield by ca. 20 % compared to bulk VPO. Almost complete conversion of 2, 6‐dichlorotoluene and 81 % yield of nitrile were observed using a 25 %VPCoO/γ‐Al₂O₃ catalyst.     

Complexometric determination of thallium(III) in pure solution,alloys, and complexes using semicarbazide hydrochloride as a releasing agent

A simple and accurate complexometric method is proposed for the determination of Tl(III) using semicarbazide hydrochloride as a releasing agent. In the presence of diverse metal ions, thallium is complexed first with a known excess of EDTA, and the surplus EDTA is then titrated with standard zinc sulfate at pH 5.0–6.0 (hexamine) using xylenol orange indicator. An excess of 5% aqueous neutral solution of semicarbazide hydrochloride is then added and the released EDTA is titrated against standard zinc sulfate solution. The method works well in the range 2–50 mg of Tl(III) with relative errors < 0.5%, standard deviations 0.05mg and coefficient of variation 0.4%. The method is applied for the determination of thallium content in complexes and alloy compositions     

New environmentally friendly solvent free synthesis of dihydropyrimidinones catalysed by N-butyl-N,N-dimethyl-α-phenylethylammonium bromide

N-Butyl-N,N-dimethyl-α-phenylethylammonium bromide catalyzes efficiently the three component condensation reaction of an aromatic aldehyde, a β-keto ester and urea/thiourea under solvent free conditions at 100°C to afford the corresponding dihydropyrimidinone in high yield.     

Spectrophotometric determination of vanadium(V) and its application to vanadium steel containing chromium,molybdenum, manganese,and nickel

Promethazine hydrochloride forms a red colored species with vanadium(V) in 6.0–7.5 M phosphoric acid. A 16-fold molar excess of the reagent is necessary for full development of color intensity. Beer's law is valid over the concentration range of 0.1–7.0 ppm. The optimum concentration range as evaluated by Ringbom's method is 0.5–7.0 ppm. The sensitivity of the reaction is 0.005 μg cm^?2 and the molar absorptivity is 9.60 × 10³ liter mol^?1 cm^?1 at 517 nm. The effects of acidity, time, temperature, order of addition of reagents, reagent concentration, and the interferences from various ions were reported. Vanadium in vanadium steel containing chromium, molybdenum, manganese, and nickel was determined.