Search results for "Heck reaction"
showing 8 items of 28 documents
Practical Synthesis of Vinyl-Substitutedp-Phenylenevinylene Oligomers and Their Triethoxysilyl Derivatives
2001
Luminescent semiconducting organic compounds are widely used as active layers in electro-optical devices. Apart from conjugated polymers, monodisperse oligomers also represent attractive materials. The synthesis of stilbenoid oligomers with polymerizable end groups is presented. Oligo(phenylenevinylene)s with terminal vinyl groups 17–19 are prepared in good yields by Horner–Emmons olefinations or by the Heck reaction of the iodo-substituted oligomers 15, 16 with compressed ethene. Triethoxysilyl groups can be linked via rigid 1,2-vinylene units to the chromophores 26–30, either in the direct reaction of 14, 24 with silanes 21, 22 or by cross-metathesis of 17–19 with the vinylsilanes 21, 22 …
Optically active amphiphilic hyperbranched polyglycerols as templates for palladium nanoparticles
2006
Abstract We report a systematic study on the encapsulation of palladium nanoparticles in optically active amphiphilic hyperbranched polyglycerols with different optical signs and different degrees of polymerization, namely (−)-P(G 40 C16 0.5 ) 1 and (+)-P(G 73 C16 0.5 ) 2 . Several issues have been addressed here: (a) relatively wide size distributions (1–5 nm) of palladium nanoparticles have been achieved, (b) a remarkable template effect ( 1 , DP n = 40, 1.2 ± 0.1 nm; 2 , DP n = 73, 2.3 ± 0.1 nm average particle size) has been observed using TEM technique, as shown by the particle size dependent on the degree of polymerization of the polymers, (c) NaBH 4 is found to be a convenient redu…
ChemInform Abstract: Sustainable Carbon-Carbon Bond Formation Catalyzed by New Oxamate-Containing Palladium(II) Complexes in Ionic Liquids.
2014
New and versatile bis(oxamato)palladate(II) complexes (I) are synthesized and investigated for both Suzuki and Heck coupling reactions in molten tetra-n-butylammonium bromide as ionic liquid.
Syntheses of polyfunctionalized resveratrol derivatives using Wittig and Heck protocols
2012
Improved protocols for Wittig reaction and palladium-catalyzed Heck coupling give expedient access to a series of unprecedented polyfunctionalized artificial-resveratrol derivatives. In the modified Wittig protocol, trimethylsilyl was used as a highly valuable protective group of the phenolic functions of starting aromatic materials. A clean O-alkylation of hydroxylated stilbenes with ethylene carbonate was also conducted. Thus, Wittig reaction followed by hydroxyethylation take place one-pot with only carbon dioxide as waste. Additionally, a palladium-catalyzed Heck coupling strategy was developed by using ferrocenyl phosphane ligands, and multi-functionalized hydroxylated stilbenes were o…
Templating effect of carbon nanoforms on highly cross-linked imidazolium network: Catalytic activity of the resulting hybrids with Pd nanoparticles
2019
Two different carbon nanoforms (CNFs), namely multi-walled carbon nanotubes (MWCNTs) and carbon nanohorns (CNHs), have been chosen as support for the direct polymerization of a bis-vinylimidazolium salt. Transmission electron microscopy analyses revealed a templating effect of the CNFs on the growth of the polymeric network, which perfectly covers their whole surfaces creating a cylindrical or spherical coating for MWCNTs and CNHs, respectively. Subsequently, the CNFs-polyimidazolium have been used as stabilizers for Pd nanoparticles (Pd NPs), and the obtained materials have been characterized by means of analytical and spectroscopic techniques and then employed as easily recoverable and re…
The first catalytic method for Heck alkynylation of unactivated aryl bromides (copper-free Sonogashira) in an ionic liquid: 1 mol-percent palladium/t…
2007
Herein we report the studies of Heck alkynylation (copper-free Sonogashira) with aryl halides (I, Br, Cl) employing various metallic precursors, tertiary phosphanes and bases in [BMIM][BF4] as the solvent. As a result, we provide the first method that allows the coupling of a large array of substrates, either activated or deactivated bromides in an ionic liquid. Furthermore, the system of highest efficiency is unexpectedly the simplest and cheaper combination that employs [Pd(η3-C3H5)Cl]2/PPh3 at only a 1 mol-% loading with pyrrolidine as the base and in the absence of a copper salt. The coupling of sterically and electronically deactivated bromides bearing different functional groups to ar…
Cross-Linked Thiazolidine Network as Support for Palladium: A New Catalyst for Suzuki and Heck Reactions
2015
A thiazolidine-based material was used for the first time as support for palladium. The support was prepared by starting from a highly cross-linked thiazolium-based material, obtained by radical oligomerization of a bisvinylthiazolium dibromide salt in the presence of 3-mercaptopropyl-modified silica SBA-15. Palladium was immobilized by treatment with tetrachloropalladate salt. Reduction with sodium borohydride afforded a thiazolidine-based material that acted as ligands for the Pd species. The thiazolidine-based palladium catalyst was fully characterized and, working in only 0.1 mol% amount, displayed good activity in the Suzuki-Miyaura and in the Heck reactions. Several biphenyl and alken…
Thiophene based imino-pyridyl palladium(II) complexes : Synthesis, molecular structures and Heck coupling reactions
2017
The new compounds (5-methyl-2-thiophene-2-pyridyl(R))imine [R = methyl (L1); R = ethyl (L2)] and (5-bromo-2-thiophene-2-pyridyl(R)imine [R = methyl (L3); R = ethyl (L4)] were successfully synthesized via Schiff base condensation reaction and obtained in good yields. These potential ligands were reacted with [PdCl2(COD)] and [PdClMe(COD)] to give the corresponding complexes [PdCl2(L)] (L = L1-L4; 1–4) and [PdClMe(L)] (L = L1-L4; 5–8). All compounds were characterized by IR, 1H and 13C NMR spectroscopy, elemental analysis and mass spectrometry. The molecular structures of 1, 2, 6 and 8 were confirmed by X-ray crystallography. The complexes were evaluated as catalyst precursors for standard He…