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Effetto dei liquidi ionici nelle reazioni di formazione del legame C-C catalizzate da complessi Palladio-carbenici del benzotiazolo
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Effects Exerted by Ionic Liquids on Heck Reaction Catalysed by Palladium Benzothiazole Carbene Complex
No full textStereoselective Synthesis of 1,4-Dienes by Chelation-controlled Reduction of Benzothiazole beta-Oxosulfides
No full textAllylated ~-oxosulfides of benzothiazole can replace ~-oxophosphane oxides to provide a
stereospecific alkene synthesis. These sulfides, by reduction with sodium borohydride afford
predominantly syn beta-hydroxy sulfides. DIBAL reduction in the presence of magnesium bromide
improves the syn stereomer formation. Base treatment of these [3-hydroxy sulfides affords (Z)-ailyl
thiiranes which are converted into (E, Z)-diene
Regio- and Stereo-Selective Carbon-Carbon Bond Formation in Ionic Liquids
No full textIonic liquids, that is molten salts, may represent activating and stabilizing solvents for C–C coupling reactions. In particular, tetrabutylammonium
bromide (TBAB) is particularly suitable for Heck reactions as it enhances reaction rates. In the presence of tetrabutylammonium
acetate as base, palladium complex with benzothiazolidene as ligands as well palladium acetate are transformed to Pd-nanoparticles which
allow regio- and stereo-specific Heck reactions with very high TON and TOF. Beside this, TBAB enhances, by solvation, the formation and
reactivity of carbanions. A comparative study on effects exerted by different ionic liquids on catalyst stabilization, reaction rates and regioand
stereo-selectivity in the C–C coupling reactions is also reported
Pd–benzothiazol-2-ylidene complex in ionic liquids: Efficient catalyst for carbon–carbon coupling reactions
No full textPd-benzothiazol-2-ylidene complex 3 catalyzes efficiently the carbon–carbon coupling reactions in the ionic liquid tetrabutylammonium
bromide (TBAB) as solvent. The IL does exert a striking influence on the reactivity and the stability of the catalyst.
This is probably due to the formation, by reaction with TBAB, of an anionic and more nucleophilic complex surrounded by large
tetrabutylammonium cation that would impede, by imposing a Coulombic barrier for collision, the formation of clusters growing
further into catalytically inactive metal particles. On the contrary, ionic liquids with planar structures and poor nucleophilic anions
like the [bmims], that form tight ion pairs, are barely efficient in influencing the reactivity and stability of the catalyst
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