Reaction with Group 15 fluorides

Glycosylfluorides. The anomeric hydroxyl or acetoxy group of monosaccharides is converted into a fluoro group by reaction with Olah s reagent in 70-90% yield. This reaction is useful for preparation of the thermodynamically more stable P-glycosyl fluoride (p/a >95 5). 

Trimethylsilylamino tellurium pentafluoride lost the trimethylsilyl group in reactions with hydrogen fluorideS cesium fluoride, chlorine fluoride, sulfur fluorides, selenium tetrafluo-ride, phosphorus pentafluoride, tungsten hexachloride, molybdenum hexafluoride, and tungsten hexafluoride. ... 

If the silica is treated with fluoride prior to titanation, which converts many of the silanol groups into Si-F surface groups, the reaction with titanium alkoxide is inhibited and the treatment is less effective. The data in Table 34 illustrate this outcome. Silica samples were treated (or not) with two fluoride compounds in aqueous solution, then they were dried at 260 °C in the normal way prior to titanation. Titanium isopropoxide was added to make the catalyst contain 5 wt% Ti. Each sample was then calcined at 815 °C in air. Chromium was applied (0.5 wt%) as bis(f-butyl) chromate) in hexane solution (two-step activation, see Section 12). After final activation in air at 315 °C, each sample was tested at 102 °C, and the polymer MI values obtained are listed in the table. The change in MI shows that the titanium did not attach well to the carrier in the presence of fluoride. As more fluoride was added, the polymer MI dropped. 

Sulfonylation. The iodine atom of fluoroalkyl iodides suffers oxidation and is then replaced by a sulfonic acid group on reaction with Na2S20s. On further treatment with chlorine and then with KF the sulfonyl fluorides are readily synthesized. 

Reactions are described in which the chlorine atom in the pyridinium chlorodithiophosphate betaine (123) is replaced by fluoro-, bromo-, and dimethylamino-groups further reactions with alcohols give alkoxydithio-phosphates, of which the fluorides (124) are particularly stable. The... 

In addition, they contain extra components. Part of the filler phase is made up of particles of fluoroaluminosilicate glass of the type used in glass-ionomer cements. There is also a small quantity of a proprietary acid-functional monomer, the so-called acid resin [ 1 ]. This is not sufficient to allow the monomer to be soluble in water, but it does confer a small degree of hydrophilic character on the set matrix. This causes water from the surroundings to be drawn into the structure, and results in ionization of the acid-functional groups and reaction with the ionomer glass component [38]. Any such reaction is limited, but potentially useful in allowing the set material to release fluoride. 

Chlorination is carried out m a manner similar to brommation and provides a ready route to chlorobenzene and related aryl chlorides Fluormation and lodmation of benzene and other arenes are rarely performed Fluorine is so reactive that its reaction with ben zene is difficult to control lodmation is very slow and has an unfavorable equilibrium constant Syntheses of aryl fluorides and aryl iodides are normally carried out by way of functional group transformations of arylammes these reactions will be described m Chapter 22... 

Fluorine and selenium, in the form of a phenylselenenyl group, add to nucleophilic olefins with Markovnikov regioselectivity and anti stereoselectivity on reaction with several reagents that may form phenylselenenyl fluoride in situ [792, 193, 194] (equation 30)... 

Bu4N F , THF, 25°, I h, >90% yield. Fluoride ion is very basic, especially under anhydrous conditions, and thus may cause side reactions with base-sensitive substrates. The strong basicity can be moderated by the addition of acetic acid to the reaction, as was the case in the following reaction, after all others methods failed to remove the TBDMS group. ... 

Tetrabutylammonium fluoride (TBAF) is usually used in the form of the trihydrate or as a solution in tetrahydrofuran (THF). The pure form is difficult to isolate, owing to decomposition to FFF, tributylamine, and but-l-ene [18, 19] on dehydration. It has been used for a variety of reactions, including as a catalyst for various reactions with silicon compounds [20, 21]. One of its main uses is in the cleavage of silyl ether protecting groups [22]. 

---