Cyclic α, β-epoxysilanes: Acid-catalysed reactions of 1-trimethylsilylcyclooctene oxide

The acid-catalysed reactions of medium ring α,β-epoxysilane 1 are described. The epoxide 1 gives exclusively the bicyclic alcohol 2 with boron trifluoride etherate. With aqueous sulphuric acid the products are due to both transannular ring closure, 2, and transannular hydride migration, 3 and 4. trans-Cyclooctene derivatives 3 and 4 are formed by the trans-elimination of trimethylsilanol from the likely intermediate β-hydroxysilanes 10 and 11. The results with methanolic sulphuric acid are similar. It is also noticed that the hydride migration is facilitated by the nucleophilic strength of the medium.     

Synthesis,ABTS-Radical Scavenging Activity,and Antiproliferative and Molecular Docking Studies of Novel Pyrrolo[1,2-a]quinoline Derivatives

A new 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)-radical scavenging and antiproliferative agents of pyrrolo[1,2-a]quinoline derivatives have been synthesized. An efficient method for the synthesis of 14 novel diversified pyrrolo[1,2-a]quinoline derivatives has been described using 4-(1,3-dioxolan-2-yl)quinoline and different phenacyl bromides in acetone and followed by reacting with different acetylenes in dimethylformamide/K₂CO₃. The structure of the newly synthesized compounds was determined by infrared, ¹H NMR, ¹³C NMR, mass spectrometry, and elemental analysis. The in vitro antioxidant activity revealed that among all the tested compounds 5n exhibited maximum scavenging activity with ABTS. Compound 5b has showed good antiproliferative activity as an inhibitor of epidermal growth factor receptor (EGFR) tyrosine kinase.     

Trimethylsilylcyclooctadiene-transition metal complexes: metal-catalysed protodesilylation of cyclic vinylsilanes, and transfer hydrogenation promoted by the displaced silyl group

Complexes of 1-trimethyisilyl-1,5-cyclooetadiene (TMS-COD, 2) with Ag^I, Rh^I, Pd^II and Pt^II have been prepared and characterised. The distortion in their structures in comparison with the near symmetrical structures of the corresponding 1,5-clooctadiene (COD, 1) complexes, which is obviously attributable to the presence of vinylic SiMe₃ group, is clearly indicated by their ¹H and ¹³C NMR spectral characteristics. The silver complex is somewhat unstable, but the other complexes are quite stable. An unstable Cu^I complex that could not be satisfactorily characterised was also obtained. If appropriate conditions for the preparation of Rh and Pd complexes are not maintained, desilylation occurs, accompanied by reduction of COD to cyclooctene by transfer of hydrogen from the solvent alcohol. The displaced silicon containing moiety seems to enhance the transfer hydrogenation. Attempts to prepare Ru^II complex resulted in the formation of a complex of desilylated diene (Ru^II-COD).     

Phase stabilization in cinnarizine complexes using X-ray profile analysis

Characterization of cobalt(II), cadmium(II), copper(II) and tin(II) cinnarizine complexes have been carried out using conductivity, electronic spectra, infrared, nmr, thermogravimetric and X-ray analyses to establish the nature of phase stabilization in these materials. Also, the intrinsic strain components present in these materials during the formation have been computed using wide-angle X-ray scattering analysis. The variation of the crystallite shape ellipsoid in these materials has been discussed on the basis of Hosemann’s paracrystalline model.     

Hydrogen Bonded Channel Formation in a Molecular Complex: <Emphasis Type="Italic">cis-</Emphasis>1-Chloro-2-ammonium-1-trimethylsilylcycloheptane Picrate

Abstract  The crystal and molecular structure of cis-1-chloro-2-amino-1-trimethylsilylcycloheptane picrate (cis-CATP) is determined and discussed along with its spectroscopy. The crystal structure of this compound (C₁₀H₂₃SiClN⁺ C₆H₂N₃O₇⁻) consists of ammonium cycloheptane cation and picrate anion stabilized by interionic N–H···O and C–H···O interactions leading to extended hydrogen bonded network structure. Apart from the less common syn addition of nitrosylchloride to 1-trimethylsilylcycloheptene ring, an interesting and unexpected reversal of regiochemistry of addition is revealed. Index Abstract  The preparation of cis-1-chloro-2-ammonium-1-trimethylsilylcycloheptane picrate is described and its crystal structure is determined and discussed.      

A facile route to bicyclo[3.3.0]octanes through clean transannular cyclisation of 1-trimethylsilylcyclooctene under friedel-crafts condition

A wide range of exo-cis-bicyclo[3.3.0]-2-octyl ketones are obtained by the reaction of 1-trimethylsilylcyclooctene with various acyl clorides in presence of aluminium chloride.     

Catalytic epoxidation of cyclic vinylsilanes by ruthenium(II) complexes under aerobic conditions

A new methodology has been developed for the catalytic epoxidation of cyclic vinylsilanes using a ruthenium(II) bisoxazoline complex 2 with molecular oxygen. An attempt has been made to understand the role of -SiMe₃ group on the rate of epoxidation process.     

A rapid synthesis of quinoxalines starting from ketones

A fast and general synthesis of quinoxalines, performed in two stages or as a one-pot reaction, starting from ketones via their α-hydroxylimino ketone derivatives, and condensation of the latter with 1,2-diaminobenzene under microwave irradiation, is described.     

A simple spectrophotometric method for the determination of phosphate in soil, detergents, water, bone and food samples through the formation of phosphomolybdate complex followed by its reduction with thiourea

A simple spectrophotometric method is developed here for the determination of phosphate present in the samples of soil, detergents, water, bone and food based on the formation of phosphomolybdate complex with the added molybdate followed by the reduction of the complex with thiourea in aqueous sulfuric acid medium. The system obeys Beer's law at 840 nm in the phosphate concentration range, 0.5-10.0 μg/ml. Molar absorptivity, correlation coefficient and Sandell's sensitivity values are found to be 1.712 mol(-1) cm(-1), 0.9769 and 0.0555 μg cm(-2) respectively. For a comparison of the results determined from the developed method, phosphate present in the same set of samples is determined separately following an official method. The results of the developed method are agreeing well with those of the official phosphomolybdate method.