Selective Propargylation of Carbonyl Compounds and Imines with Barium Reagents

A Barbier‐type regioselective propargylation of aldehydes and ketones with (3‐bromobut‐1‐ynyl)trimethylsilane has been achieved using reactive barium as a low‐valent metal in THF. Especially in the case of ketones, the corresponding homopropargylic alcohols form almost exclusively. In the reaction of α,β‐unsaturated carbonyl compounds, only 1,2‐adducts have been observed. This method is also applicable to propargylation of imines, and the corresponding homopropargylic amines are obtained regiospecifically in good yields with diastereomeric ratios of up to 87:13.     

Catalysis by Ir(III), Rh(III) and Pd(II) metal ions in the oxidation of organic compounds with H2O2

Catalytic activities of three transition metals, as iridium (III) chloride, rhodium (III) chloride and palladium (II) chloride, were compared in the oxidation of six aromatic aldehydes (benzaldehyde, p‐chloro benzaldehyde, p‐nitro benzaldehyde, m‐nitro benzaldehyde, p‐methoxy benzaldehyde and cinnamaldehyde), two hydrocarbons (viz. (anthracene and phenanthrene)) and one aromatic and one cyclic alcohol (cyclohexanol and benzyl alcohol) by 50% H₂O₂. The presence of traces (substrate: catalyst ratio equal to 1:62500 to 1:1961) of the chlorides of iridium(III), rhodium(III) and palladium(II) catalyze these oxidations, resulting in good to excellent yields. It was observed that in most of the cases palladium(II) chloride is the most efficient catalyst. Conditions for the highest and most economical yields were obtained. Deviation from the optimum conditions decreases the yields. Oxidation in aromatic aldehydes is selective at the aldehydeic group only and other groups remain unaffected. This new, simple and economical method, which is environmentally safe, also requires less time. Reactive species of catalysts, existing in the reaction mixture are also discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Analysis of primary aliphatic short-chain monoamines by LC in water samples

Several derivatization procedures with o-phthaldialdehyde-N-acetylcysteine (OPA-NAC) were compared for a rapid analysis of primary aliphatic short-chain monoamines in water samples by HPLC using a LiChorospher analytical separation column (100RP₁₈ mm i.d., 5 μm). Both the solution and the solid-support assisted off-line derivatization on C₁₈ SPE cartridges were inadequate options because of beginning degradation processes of the instable isoindol derivatives during their transfer to the analytical column. This problem was precluded with the on-column or solid-support assisted on-line derivatization. In the last mentioned procedure, the derivatization took place in a Hypersil C₁₈ precolumn ( mm i.d., 30 μm) connected with an additional preconcentration step resulting in better detection limits (0.002-0.040 μg ml⁻¹ requiring only 150 μl of water sample) than in the on-column procedure (0.08-0.16 μg ml⁻¹). The improved sample handling, the better control of parameters affecting reaction rates, the fully automation of this method with only 10 min analysis time for each sample are further advantageous. The potential of the solid-support assisted on-line derivatization was outlined and applied to water samples from several sources. Recovery values near 100% were obtained.     

Synthesis of naphthyridines and phenanthrolines using catalysts based on transition and rare-earth metals

Liquid-phase condensation of 3-, 4-, and 8-aminoquinolines with aliphatic and aromatic aldehydes catalyzed by transition and rare-earth metal complexes is an efficient method for synthesis of substituted 1,7- and 1,6-naphthyridines and 1,10-phenanthrolines.Institute of Organic Chemistry, Ural Branch, Russian Academy of Sciences, 450054 Ufa; Eastern Scientific-Research Institute of Coal Chemistry, 620219 Sverdlovsk. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 5, pp. 1139–1148, May, 1992.     

Enantioselective Organocatalytic Aza-Michael Additions of Phthalimide Derivatives to α,β-Unsaturated Aldehydes

Phthalimide derivatives as nitrogen nucleophiles with α,β‐unsaturated aldehydes for asymmetric aza‐Michael additions have been reported. The reactions proceed smoothly to afford corresponding Michael adducts in good yields (up to 98%) and enantioselectivities (up to 95% ee).     

A Novel Synthesis of α-Tellanyl α,β-Unsaturated Aldehydes Using α-Tellanyl β-Alkoxyalkenyl Lithiums

Abstract

β-Ethoxy-α-phenyltellanylvinyl lithiums were successfully generated in situ from phenyltellanylacetaldehyde diethyl acetal with lithium 2,2,6,6-tetrame-thylpiperidide (LTMP) and underwent methylation or nucleophilic addition with aldehydes and ketones. The successive dehydration of the allylic alcohols with trimethylsilyl trifluoromethanesulfonate (TMSOTf) gave α-phenyltellanyl α,β-unsaturated aldehydes, which transformed to some useful compounds.     

Convenient,mild and rapid synthesis and characterization of some Schiff-base ligands and their complexes with uranyl(II) ion

Some Schiff-base complexes of UO₂(II) ion derived from 2-hydroxyacetophenone and aliphatic diamines under reflux conditions have been synthesized. The resulting ligands and their complexes have been characterized by elemental analyses (C, H, N), infrared, ¹H NMR, ¹³C NMR and mass spectra. In these efficient reactions, Schiff-base complexes with important applications in analytical and organic chemistry are prepared.     

Silica surface modification using different aliphatic chain length silane coupling agents and their effects on silica agglomerate size and processability

Silica surface was treated with various aliphatic chain length silane coupling agents and compounded in EPDM using an internal mixer, and their agglomerate sizes, viscosity, and extrudate swell were investigated. The treated silica compounds showed smaller agglomerate size, lower viscosity, and lower swell reduction compared to untreated silica compound after equivalent mixing times. Short chain silane treated silica compound exhibited smallest agglomerate size. Silane acted as dispersing agents and processing aids in silica/EPDM compounds.     

Is the neutral Knoevenagel reaction initiated by the carbanion formation?

The title reactions were studied by means of the density functional theory calculations. A base promoted reaction (called here ‘B’) was traced in a model composed of benzaldehyde, malononitrile, and (H₂O)₁₁. A neutral model (‘N’) of Ph‐CHO, H₂C(CN)₂ and (H₂O)₁₂ was also examined in line with a reported clean reaction. It was found that the ion pair of HC(CN) and H₃O⁺ is generated at the first step for N. For B, there are five elementary processes, and for N, four ones were obtained. By RB3LY/6‐311 + G** SCRF = PCM//RB3LYP/6‐31(+)G* energy calculations, the rate determining steps for both B and N reactions are the second proton removal, TS5(B) and TS3(N), respectively. In both B and N, the neutral species Ph(HO)HC‐CH(CN)₂ is the key intermediate. Copyright © 2010 John Wiley & Sons, Ltd.