Sulfonium fluoride, tris catalyst

When activated by anionic catalysts [potassium fluoride, cesium fluoride, tctraalkylammonium fluorides, tris(dimethylamino)sulfonium difluorotrimethylsilicate, phosphazenium, hexa-methylpiperidinium and cobaltoccnium fluorides, tetrabuiylammonium difluoro(triphenyl-silyl)silicatc. the complex tetrakis(dimethylamino)ethene/pcrfluoropropene, ammonium (and phosphonium) periluorocyclobuianc ylides], trimethyl(perfluoroalkyl)silanes will generate C-Rp bonds from carbon-halogen bonds. 

Fujita and Hiyama have developed a homogeneous fluoride ion catalyst system consisting of tetrabutylammonium fluoride (TBAF) or tris(diethylamino)sulfonium difluorotiimethylsilicate (TASF) in hexamethylphosphoric triamide (HMPA), which can promote and complete the hydrosilylation of aldehydes and ketones at room temperature or lower temperatures within one hour in most cases (equation The relative... 

The degree of polymerization obtained is determined by the molar ratio of [monomer] to the [initiator (TMS)], with the catalyst concentration determining the rate of polymerization. The catalyst can be a nucleophilic entity, with the best effects being obtained with fluoride (F ) or bifluoride (HF2 ) anions derived from salts soluble in the reaction medium, such as tris(dimethylamino)sulfonium bifluoride and tetrabutylammonium fluoride. These catalysts are particularly well suited to the polymerization of methacrylic monomers. 

Group transfer polymerization (GTP) requires either a nucleophilic or Lewis acid catalyst. Bifluoride (HF2) and fluoride ions, supplied by soluble reagents such as tris(dimethylamino)-sulfonium bifluoride, [(CH3)2N]3SHF2, and (w-C NF, are the most effective nucleophilic catalysts, although other nucleophiles (CN , acetate, p-nitrophenolate) are also useful. Zinc... 

It is a palladium-catalyzed cross-coupling reaction between organosilanes (vinyl, ethynyl and allylsilanes) and organic halides (aryl, vinyl and allyl halides). Allylpal-ladium chloride dimmer [( ri -C3H5PdCl)2] and either tris(diethylamino)sulfonium difluorotrimethylsilicate (TASF) or tetra-n-butylammonium fluoride (TBAF) are used as catalysts. Fluoride ion acts as an activator for the coupling, forming an intermediate hypervalent anionic silicon species, which can then transmetallate with palladium as a preliminary reaction to coupling. 

Trimethyl(trifluoromethyl)silanc is easily fluorodesilylated by tris(dimethylamino)sulfonium difluorotrimethylsilicate [TASF(Me)], tetrabutylammonium fluoride, or tris(diethylamino) (methylamino)phosphonium hydrogen difluoride and, if arenesulfonyl fluorides are used to trap the trifluoromethyl anion, trifluoromethyl sulfones arc formed in high yield. Trisfdiethyl-amino)(methylamino)phosphonium phenolate is also an effective catalyst for this reaction, but TASF(Me) is favored as it can achieve the quantitative transformation of ArS02F into aryl trifluoromethyl sulfones.115-117... 

In the presence of a fluoride ion generating reagent such as tris(diethylamino)sulfonium difluorotri-methylsilicate (TASF, 99) and a palladium catalyst, vinyltrimethylsilane couples with vinyl and aryl iodides." For substituted vinylsilanes, the fluorodimethylsilyl group is particularly effective in the coupling reaction, which takes place with retention of configuration of both substrates (Scheme 17). Silicon-based C—C bond formation is as useful as that which employs organoborons " for the synthesis of stereo-defined conjugated dienes. 

A number of oi ganoaluminum reagents, especially Me2AlCl, have been found to be effective catalysts for reactions of enol silyl ethers with aldehydes.It is possible that in these reactions, aluminum enol-ates may be involved as the intermediates. Similarly, bismuth trichloride has been reported to be an efficient catalyst.Since BiCh is considered to be a weak Lewis acid, the involvement of a bismuth enolate is perhaps implicated. Enolate intermediates are definitely generated when tetraalkylammonium fluorides or tris(dialkylamino)sulfonium (TAS) difluorotrimethylsiliconates (104) are used as reagents to promote the reactions of enol silyl ethers. Their chemistry will therefore not be discussed in this chapter. 

The most effective nucleophilic catalysts for this reaction are bifluoride (HF2) and fluoride ions. They can be generated from soluble reagents like tris(dimethylamino)sulfonium bifluoride. Other... 

Anionic catalysts work by coordination to the silicon atom they are needed in only small amounts ( 0.01% based on the initiator) and are used preferably for methacryhc monomers [232]. The anionic moiety comprises fluoride, azide, and cyanide, but also carboxylates, phenolates, sulfmates, phophinates, nitrite, and cyanates [232,236,237]. These anions are often used in combination with their corresponding adds as biacetate, H(CH3COO)J or bifluoride, (HF2) . The counterions are usually tetraalkyl ammonium or tris(dimethylamino)sulfonium, [(CH3)2N]3S" (TAS). The most widely used catalysts are TASHF2 and TASF2SiMe3 [239]. To accelerate the reactivity of potassium bifluoride, KHF2, a crown ether (18-crown-6)-supported polymerization has been carried out [240]. 

The Hiyama-Hatanaka cross-coupling reaction is a more recent arylation coupling reaction that was reported by these workers in 1988 [12e, 31]. These workers demonstrated that trimethylsilylethy-lene reacts with aryl halides in the presence of a Pd(0) catalyst, a base, and a source of fluoride ion to give styrene derivatives [12e]. The source of Pd can be (it-CjHjPdCOj, Pd(Ph3P)4, or even Pdjfdbalj the base could be a hydroxide, an acetate, a phosphane, or a phosphite and the source of the fluoride ion could be tris(diethylamino)sulfonium difluoro(trimethyl)silicate (TASF), tetrabutylammonium fluoride (TBAF) or even KF (See Scheme 1.14a). The role of this reagent is shown in the catalytic cycle... 

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