Fluorides supported

The use of cesium fluoride is limited because of its cost and its availability as a truly anhydrous reagent. Its use with 18-crown-6 shows a 5 times higher rate for the formation of benzyl fluoride from benzyl bromide when compared with cesium fluonde or potassium fluoride supported on calcium fluoride [21] Either cesium fluoride or potassium fluoride supported on calcium fluoride (Procedures 5a and 5b, p 194) provides about a twofold improvement over either unsupported alkali metal fluoride [55, 69], Cesium fluoride and Aliquat 336 convert benzyl bromide to the fluoride in 94% yield. Using tetrabuty lammonium fluoride in place of Aliquat... 

Sa. Preparation of Benzyl Fluoride by Using Potassium Fluoride Supported on Calcium Fluoride (Methanol Procedure) [5-S]... 

Silver(I) fluoride supported on calcium fluoride has been shown to improve fluoride nuc-leophilicity for halogen exchange. Iodides give the best yields. 1-Iodooctane (1) is converted to 1-fluorooctane (2) in 80% yield.1... 

Calcium fluoride supported on cesium fluoride gives also a good conversion rate of 95% for benzyl bromide (3) to benzyl fluoride (4). The reaction is, however, carried out in tetramethylene sulfone. 

Several patents report the use of calcium fluoride supported on potassium fluoride or calcium fluoride itself for halogen-fluorine exchange.4-6 These products obtained are useful in the pharmaceutical and agrochemical industries. 

Reaction of organosUanes with lactones and enonesf Certain carbanions, generated by desilylation, have been found to react not only with aldehydes and ketones, but also with some lactones and a,/ -enones. Cesium fluoride or tetrabutylam-monium fluoride supported on silica can be used as catalysts. 

Bessarabov s devices use composite membranes consisting of a thin silicone rubber polymer layer coated onto a microporous poly(vinylidene fluoride) support layer. These membranes have high fluxes and minimal selectivities for the hydrocarbon gases, but the dense silicone layer provides a more positive barrier to bleed-through of liquid than do capillary effects with simple micro-porous membranes. 

The adsorption of sulfate on polycrystalline Pt electrodes has been studied many times [35, 36, 38, 139, 140, 142]. Spectra taken in the presence of a fluoride supporting electrolyte at different pH values are given in Fig. 57. The knowledge gained from the studies on single crystals makes necessary a revision of the interpretation of the data in [38] and [142]. It was assumed [142] that the static electric field activates asymmetric modes, a fact that seems to be less probable according to the results at Pt single crystals. 

Ylide generation on alumina or potassium fluoride supported on alumina is of interest since the use of a solvent is unnecessary. ... 

C and removing the more volatile impurities in vacuo [1083]. Silver fluoride (supported as a film on copper) is also reported to act as a catalyst for this reaction, permitting the combination to take place rapidly, smoothly, and without explosion [2159a]. Neither caesium fluoride nor aluminium were found to be active [2159a]. 

In a related transformation, cyclopropanes 7 were obtained from active methylene compounds and electron-deficient alkenes by the action of iodine and potassium fluoride supported on solid alumina. 

Basu et al. have reported palladium-catalyzed selective cross coupling of bromo-pyridines and amines on the surface of potassium fluoride supported basic aluminium oxide [5]. For example, amination of 2,6-dibromopyridine by this method afforded the monoaminated products predominantly, even after prolonged the reaction time and using excess amine, whereas previous method [6] gave only bis-aminated products (Scheme 5.3). 

Scheme 5.3 Palladium-catalyzed selective cross coupling of bromopyridines and amines on potassium fluoride supported basic aluminium oxide.

Among these families of solid bases, we have particularly developed three new types of catalysts derived from these "classical" solid bases. The first two ones (MgLa mixed oxides and alkali fluorides supported on a alumina) were applied to fine chemistry [11-16] while in the third case (supported CuO) we studied the role of the basic strength of this oxidant on the selective adsorption of NO in the NOx trap technology [17]. In each case, we found a fundamental effect of the active species dispersion on the catalyst basic strength and reactivity. 

Extensive recycling of organic and HF is required and catalyst lifetime is a problem. However, subsequent work by Dupont [8] over a variety of metals on an aluminium fluoride support gave extended catalyst lifetimes. 

C ampelo, JM Climeiu. MS Marinas, JM. Michael addition of niiromcihanc to 3-buten-2-onc catalyzed by pinassium fluoride supported on alumina, zinc oxide, tin dioxide, scpiolilc, aluminum phosphate. AlP04-AI Oi and AIP04-ZnO. Reaction Kinetics and Catalysis Letters. 1992 47, 7-11. 

By employing arylsulfonyl groups as suitable leaving groups, a highly stabilised carbocation could be generated using potassium fluoride supported on alumina, which then allowed for easy interception by the thus-formed nucleophilie enamine intermediate from the aldehyde and L-proline (Scheme 5.24). 

The use of neutral alumina can lead to multiple addition reactions, but basic alumina gives clean reactions [146]. There are many examples of the use of potassium fluoride supported on alumina being used as a catalyst for Michael additions [125, 147]. 

The insertion reaction between an isocyanide and a sulfenyl chloride generates an intermediate (e.g. equation 4.42), which can undergo 1,3-cycloaddition reactions with electron-deficient species to form pyrroles and pyrrolines. Potassium fluoride supported on alumina is a mild basic catalyst for this process [161]. 

Supported reagents which can perform partial oxidations have been reported for example, the solid base KF-alumina (potassium fluoride supported on alumina) has been found to oxidise fluorene to fluorenone very effectively (Figure 16.22) [27]. 

A cyanide supporting electrolyte Is useful for determining lead in the presence of large amounts of cadmium because the wave of the lead-cyanide complex precedes that of the cadmium complex by about 0.4 V (K5). Bismuth, antimony, - l ead and tin mixtures have been determined using a hydrochloric acld-sodlum fluoride supporting electrolyte (l6). The use of an ammonlacal tartarate soln has been found to be beneficial for the simultaneous determination of thallium and lead (B2). 

Recent Du Pont work [Du Pont U.S. Patent 4,922,037 (1990)] suggests that a variety of metals on an aluminum fluoride support provides extended catalyst life. 

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