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The three-component reaction between salicylaldehydes (I), 4-hydroxycoumarin (II) and indole (III) or barbituric acid (V) furnishes the corresponding chromeno[4,3-b]chromen-6-ones in high yields.

18 Title compounds of type (IV) or (VI) are prepared and tested as anti-HIV-1 RT inhibitors.

A very efficient and cost effective method for the alkynylation of ω-chloroalkyl tosylates is developed and applied to the synthesis of 1,2-dicycloalkylethynes (IV) and (V).

Compounds (VIIa), (VIIb) and (VIIf) exhibit moderate to strong antibacterial and antifungal activities.

A method for the preparation of anatase TiO2, which is stable to a temperature as high as 900 °C, without using any complex cationic dopants is presented. The synthetic procedure involves the reaction of titanium tetraisopropoxide (TTIP) with trifluoroacetic acid (TFA) followed by hydrolysis and sol−gel conversion to the xerogel and further calcination. The retention of the anatase phase to high temperatures can be attributed to the presence of small amounts of fluorine in the lattice, which is gradually removed between 500 and 900 °C as confirmed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopic analysis. Samples prepared with a 1:16 TTIP/TFA composition calcined at 900 °C showed significantly higher photocatalytic activity compared to the control sample, standard commercial photocatalyst Degussa P25, and samples prepared using acetic acid and oxalic acid. The high-temperature anatase phase stability, determined by X-ray diffraction and Raman spectroscopy, coupled with its ...

School of Studies in Chemistry, Vikram University, Ujjain-456 010, India E-mail: shivraj24@rediffmail.com Photochemistry & Solar Energy Laboratory, Department of Chemistry, M. L. Sukhadia University, Udaipur-313 002, India Manuscript received 14 July 2003, accepted 11 June 2004 Dibenzylideneacetonedibromide (1) gives three different products 2, 3 and 4, when its solution in chloroform is irradiated by electromagnetic radiation at different wavelengths. The structures of these products have been confirmed by spectral analysis or co-TLC and mixed m.p. with authentic samples.

This article reports an easy chemical method of synthesizing boehmite nanofibers by a modified sol-gel process involving aluminum isopropoxide precursor. Nanorods of gamma-alumina have been successfully prepared after dehydration of the viscous sol at 600 degrees C for 4 h in air. The boehmite nanofibers and gamma-alumina nanorods were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy for surface chemistry and functional groups, scanning electron microscopy, high-resolution transmission electron microscopy with selected area electron diffraction, and energy-dispersed spectroscopy for morphology and structure identification. The length of the boehmite nanofibers was found to be more than 10 mum with a crystalline lattice structure. The mechanism of formation of the boehmite nanofibers included the preferential growth along the longitudinal axis due to interaction between the solvent molecules and the surface OH- groups of hydrogen bonds. It is also suggested that the boehmite nanofibers may have formed due to the inherent instability of the planar structure of the boehmite lattice. The diameter of the gamma-alumina nanorods was found to be less than 10 nm with a varying length in the range of 50-200 nm. Boehmite to gamma-Al2O3 transformation was attributed to the loss of water molecules by internal condensation of protons and hydroxyl ions.

Department of Chemistry, College of Science, Sukhadia University, Udaipur-313 00 I, India Manuscript received 2 April 2001 Sonochemistry : Past, present and future