RESUMO
The solid-phase version of the Pd-catalyzed Hiyama reaction between a variety of aryltriethoxysilanes and immobilized aryl halides was developed. Smooth cross-coupling was achieved to afford the corresponding biaryl products in moderate to excellent yields. The described protocol would be particularly useful for the construction of 4'-substituted 1,1'-biphenyl derivatives.
Assuntos
Compostos de Bifenilo/síntese química , Paládio/química , Silanos/química , Técnicas de Síntese em Fase Sólida/métodos , Compostos de Bifenilo/química , Catálise , Silanos/síntese químicaRESUMO
Monodisperse magnetite nanoparticles modified with poly(ethylene glycol) (PEG) were synthesized using a silane functionalized PEG obtained by reacting 3-aminopropyl triethoxysilane with carboxylic acid-methoxy PEG (mPEG-COOH) using amide reactions. Transmission electron microscopy (TEM), dynamic light scattering (DLS), and zeta potential measurements show the particles are monodisperse (sigma(gv) approximately 0.2) and stable in water for pH of 3-9 and ionic strengths, up to 0.3 M NaCl. Thermogravimetric analysis coupled with TEM and DLS indicates formation of a dense graft layer on the particle surface. An analysis of the interparticle interaction energy indicates that the particles are stabilized by strong steric repulsions between PEG chains on their surface.
Assuntos
Óxido Ferroso-Férrico/síntese química , Nanopartículas/química , Nanopartículas/ultraestrutura , Polietilenoglicóis/síntese química , Silanos/síntese química , Coloides/química , Óxido Ferroso-Férrico/química , Concentração de Íons de Hidrogênio , Espectroscopia de Ressonância Magnética , Microscopia Eletrônica de Transmissão , Modelos Químicos , Tamanho da Partícula , Polietilenoglicóis/química , Silanos/química , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
To further extend our studies in the search for reversed phases with enhanced durability at high pH, zirconized silica has now been explored as an alternative support. The synthesis of the new stationary phases involves silanization of a zirconium-modified silica support with a C(18) trifunctional silane, followed by endcapping. The chromatographic properties of the C(18) phases based on zirconized silica are similar to their titanized silica counterparts. Accelerated high pH stability tests, using phosphate mobile phases and elevated temperature, have shown that the zirconized silica phases have promising advantages not only over similarly prepared non-metalized phases but also over titanized silica C(18) phases.