Three-component cyclocondensation of 5-nitrothiophene-2-carbaldehyde with cyclohexanone and <Emphasis Type="Italic">C</Emphasis>-aminotri(tetr)azoles. Formation paths of isomeric hexahydrotriazoloquinazolines

Three-component condensation of 5-aminotetrazole with 5-nitrothiofene-2-carbaldehyde and cyclohexanone selectively afforded linearly fused 9-(5-nitrothiophen-2-yl)-4,5,6,7,8,9-hexahydrotetrazolo[5,1-b]-quinazoline. Analogous reaction of 3-amino-4H-1,2,4-triazole gave a mixture of linearly and angularly fused isomeric hexahydrotriazoloquinazolines. Probable reaction paths were experimentally justified by the isolation of the corresponding intermediate products whose structure was determined with the aid of one- and twodimensional NMR techniques.     

Influence of Support Type and Metal Loading in Methane Decomposition over Iron Catalyst for Hydrogen Production

Natural gas resources, stimulate the method of catalytic methane decomposition. Hydrogen is a superb energy carrier and integral component of the present energy systems, while carbon nanotubes exhibit remarkable chemical and physical properties. The reaction was run at 700 °C in a fixed bed reactor. Catalyst calcination and reduction were done at 500 °C. MgO, TiO₂ and Al₂O₃ supported catalysts were prepared using a co‐precipitation method. Catalysts of different iron loadings were characterized with BET, TGA, XRD, H₂‐TPR and TEM. The catalyst characterization revealed the formation of multi‐walled nanotubes. Alternatively, time on stream tests of supported catalyst at 700 °C revealed the relative profiles of methane conversions increased as the %Fe loading was increased. Higher %Fe loadings decreased surface area of the catalyst. Iron catalyst supported with Al₂O₃ exhibited somewhat higher catalytic activity compared with MgO and TiO₂ supported catalysts when above 35% Fe loading was used. CH₄ conversion of 69% was obtained utilizing 60% Fe/Al₂O₃ catalyst. Alternatively, Fe/MgO catalysts gave the highest initial conversions when iron loading below 30% was employed. Indeed, catalysts with 15% Fe/MgO gave 63% conversion and good stability for 1 h time on stream. Inappropriateness of Fe/TiO₂ catalysts in the catalytic methane decomposition was observed.     

New Glycosidic Constituents of Abutilon pakistanicum

Pakisides A and B ( 1 and 2 , resp.), new catalpol‐type iridoid glycosides, and a new glycoside, 3 , of scutellarein have been isolated from the AcOEt‐soluble fraction of the whole plant of Abutilon pakistanicum, along with buddlejoside and lapachol. The structures of new compounds were elucidated by spectroscopic techniques including ¹H‐and ¹³C‐NMR (DEPT), and 2D‐NMR experiments.