Tri-tert-butylphosphine

HECK REACTIONS OF ARYL CHLORIDES CATALYZED BY PALLADIUM/TRI-tert-BUTYLPHOSPHINE (E)-2-METHYL-3-PHENYLACRYLIC ACID BUTYL ESTER AND (E)-4-(2-PHENYLETHENYL)BENZONITRILE... 

The use of tri-tert-butylphosphine has produced still higher selectivities, allowing near total control in the synthesis of (A)-vinylsilanes, including alkoxysilanes and disiloxanes.38,39 In the context of a total synthesis of an HMG-CoA reductase inhibitor, hydrosilylation with a chlorosilane catalyzed by a platinum(O) olefin complex, Pt2 [(CH2=CH)Me2Si]20 3 (also known as Karstadt s catalyst), followed by coupling with a 2,6-disubstituted aryl iodide forged a key intermediate shown in Scheme 6.38... 

Tri-tert-butylphosphine Phosphine, tri-tert-butyl- (8) Phosphine, tris(1,1 -dimethylethyl)- (9) (13716-12-6)... 

In the Pt(0)-catalyzed hydrosilation, the addition of a catalytic amount of Na(0) appears to be necessary to achieve high levels of regioselectivity (cf.. 1,1- vs 1,2-disubstituted vinylsilane). Without the inclusion of Na(0), the reaction yields a minor regioisomer, ( )-2-(dimethylphenylsilyl)-1-buten-3-ol, 2b, in a ratio of 10-15 1. The checkers found that the reaction was considerably faster and higher-yielding with 60 mg of the catalyst, bis(ii-divinyltetramethyldisiloxane)tri-tert-butylphosphine-platinum(O). 

By using tri-tert-butylphosphine as the ligand, cross-coupling with aryl chlorides can take place even at room temperature. The chloride reacts in preference to the triflate (1.204). 

One of the most important transformations catalysed by palladium is the Heck reaction. Oxidative addition of palladium(O) into an unsaturated halide (or tri-flate), followed by reaction with an alkene, leads to overall substitution of a vinylic (or allylic) hydrogen atom with the unsaturated group. For example, formation of cinnamic acid derivatives from aromatic halides and acrylic acid or acrylate esters is possible (1.209). Unsaturated iodides react faster than the corresponding bromides and do not require a phosphine ligand. With an aryl bromide, the ligand tri-o-tolylphosphine is effective (1.210). The addition of a metal halide or tetra-alkylammonium halide can promote the Heck reaction. Acceleration of the coupling can also be achieved in the presence of silver(I) or thallium(I) salts, or by using electron-rich phosphines such as tri-tert-butylphosphine. ... 

Alkylphosphines, which are good a donors, facilitate oxidative addition, while tt-acceptor hgands make it more difficult. However, steric effects must also be considered. For instance, a low reaction rate is observed for the strongly basic, bulky ligand tri-tert-butylphosphine. 

Scheme 6.9 Stille coupling of an aryl chloride employing tri-tert-butylphosphine as a ligand [29].

However, the practical use of supercritical carbon dioxide has been limited by its solvating power. Although SCCO2 dissolves most non-polar compounds of low molecular mass, many catalysts, substrates and reagents are only poorly soluble. Most recently, it was reported that Suzuki reactions proceed in good yield in SCCO2 in the presence of palladium acetate and tri-tert-butylphosphine, with DIPEA (N,N-diiso-propylethylamine) as the base (Equations 94 and 95) [137]. 

Purification by vacuum distillation (102—103 °C, 13 Torr). Handling, Storage, and Precautions the pure material is pyrophoric and must be handled under an oxygen-free atmosphere to avoid spontaneous combustion. In the absence of oxygen, it is indefinitely stable. Solutions (ca. 10%) of tri-tert-butylphosphine are not pyrophoric, but should be handled under an inert atmosphere in order to avoid oxidation to the phosphine oxide. The HBF4 salt is air-stable. Tri-tert-butylphosphine is corrosive and causes burns on contact with skin. It is incompatible with oxidizing agents. 

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