Trimethyl phosphine catalyst

Carbene ligands can replace phosphines dne to similar electronic properties. The development of NHC design concepts featnring different substituents and backbones eventually culminated in the most prominent derivative, the SIMes (SDVtes = A, A -bis[2,4,6-(trimethyl)phenyl]imidazolidin-2-ylidene) ligand that is nsed in the second and later also third generation catalysts (complexes 72, 73, 74b and 74c in Fig. 3.28) [105, 109, 114,116],... 

As with aldol and Mukaiyama addition reactions, the Mannich reaction is subject to enantioselective catalysis.192 A catalyst consisting of Ag+ and the chiral imino aryl phosphine 22 achieves high levels of enantioselectivity with a range of N-(2-methoxyphenyljimines.193 The 2-methoxyphenyl group is evidently involved in an interaction with the catalyst and enhances enantioselectivity relative to other A-aryl substituents. The isopropanol serves as a proton source and as the ultimate acceptor of the trimethyl silyl group. 

The yields were found also to increase in the presence of phosphines, particularly trimethyl or tributyl phosphine. After all the improvements of the catalyst and reaction conditions the system became by far the most active of known non-biological catalytic systems for the reduction of dinitrogen at ambient temperature and pressure. The specific activity (the rate of N2 reduction per mole of the complex) reached and even exceeded that of nitrogenase. Up to 1000 turnovers relative to the molybdenum complex can be observed at atmospheric pressure and more than 10 000 turnovers at elevated N2 pressures. 

Propargylic alcohols are less reactive than their esters, and their carbonylation has been carried out under somewhat harsh conditions (100 °C, 100 atm) [10,11]. The carbonylation products under these conditions are different from those obtained by the carbonylation of the corresponding carbonates under milder conditions. Carbonylation of propargyl alcohol (82) in methanol without using a phosphine ligand proceeded in the presence of hydrochloric acid to afford dimethyl itaconate (79) as a main product and trimethyl aconitate (83) as a minor product (Scheme 11-24). PdCl2 or Pd/charcoal is an active catalyst [11]. 

Benzyl trimethyl ammonium hydroxide Cetrimonium bromide Dimethyl diallyl ammonium chloride Laurtrimonium bromide Laurtrimonium chloride Methyl tributyl ammonium chloride Tetrabutyl ammonium bromide Tetrabutyl ammonium chloride Tetrabutyl ammonium fluoride Tetra-n-butyl ammonium hydrogen sulfate Tetra-n-butyl ammonium hydroxide Tetrabutyl ammonium iodide Tetrabutylphosphonium acetate, monoacetic acid Tetrabutylphosphonium bromide Tetrabutylphosphonium chloride Tetraethylammonium bromide Tetraethylammonium hydroxide Tetrakis (hydroxymethyl) phosphonium chloride Tetramethylammonium bromide Tetramethylammonium chloride Tetramethylammonium hydroxide Tetramethyl ammonium iodide Tetraphenyl phosphonium bromide Tetrapropyl ammonium bromide Tetrapropyl ammonium iodide Tributylamine Tributyl phosphine Tributyl (tetradecyl) phosphonium chloride Trioctyl (octadecyl) phosphonium iodide catalyst, phase-transfer Tetraethylammonium chloride Tetraoctylphosphonium bromide Tri-n-butyl methyl ammonium chloride Tri methyl phenyl ammonium hydroxide catalyst, phenolics Triethylamine... 

In 2007, Ishihara and co-workers first reported that simple alkali metal phe-noxides were effective catalysts for the aldol reaction of ketones and trimethyl silane enolates in the presence of phosphine oxides, especially bidentate 1,2-(0=PPh2)2C4H4 (Scheme 21). With 10 mol% each of alkali metal phenox-ides and phosphine oxides in this aldol reaction, PhONa showed the best... 

Carbon-phosphorus bonds are formed by the Pd-catlyzed allylation of various phosphorus compounds (Scheme 13). The reaction of l-acetoxy-2-cyclohexene with LiPPh2 in refluxing THF provides an allylic phosphine in low yield (<15%). The phosphine produced deactivates the catalyst by coordination, which lowers the yield. In contrast, the reaction of LiP(S)Ph2 with l-acetoxy-2-cyclohexene takes place at room temperature to give allylic diphenylphosphine sulfides in 85% yield. ° Pd-catalyzed Michaelis-Arbuzov reaction of cinnamyl acetate with trimethyl phosphite affords a dimethyl allylic phospho-nate. With the reaction conditions being rather severe, this method may not be applicable to an allylic acetate that can produce a conjugated diene via /3-hydride elimination from the intermediate 7r-allylpalladium complex. 

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