Catalysts caesium fluoride

Diphenylamine (R, = Rj = Ph) reacts in a similar fashion [95], but bis(trifluoromethyl)amine (R, = Rj = CF3) apparently required high temperatures (up to 300 C) and extended reaction times (>12 h), in addition to the use of a caesium fluoride catalyst, to give the expected carbamoyl fluoride product [632],... 

The perfluorinated imine, CF3N=CFj, reacts with COFj and caesium fluoride catalyst in CH3CN at 150 C to give the corresponding carbamoyl fluoride, (CF3) jNC(0)F, with a conversion of 56% [632],... 

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 recent study [1762.ICI85], it was shown that gaseous methanal combines with carbonyl difluoride, over a charcoal catalyst impregnated with caesium fluoride, to form the commercially important low-temperature refrigerant difluoromethane, HFC-32, according to ... 

Depending upon the reaction conditions, ethanal can combine with phosgene to produce 1,1-dichloroethane, chloroethene, vinyl chloroformate or 1-chloroethyl chloroformate (see Section 10.3.3.1). However, imder conditions which produce 1,1-dichloroethane from phosgene and ethanal (charcoal catalyst, 150 C), carbonyl difluoride reacts (using a charcoal catalyst impregnated with caesium fluoride) to produce a mixture of the saturated 1 -fluoroethyl fluoroformate and the unsaturated vinyl fluoroformate (see Section 13.14.6.3.1). Thus, the COFj/CHjCHO/charcoal system is unstable with respect to dehydrofluorination, whilst the COClj/CHjCHO/charcoal system is unstable with respect to decarboxylation ... 

Comparison between Tables 14 and 15 clearly demonstrates that caesium fluoride is far more effective than potassium fluoride towards 2,4-dichloronitrobenzene. As some papers reported about the addition of CsF as catalyst in the Halex reaction using KF (refs. 42 - 46), we quantified the behaviour of CsF-KF mixtures to look for some synergistic effect. 

All these references provide very dispersed indications. Thus, we wished to estimate quantitatively the effectiveness of some phase-transfer catalysts under the same conditions and to compare them to caesium fluoride. 

Under conditions mentionned in Table 21, tetramethylammonium chloride is more effective than caesium fluoride to improve the Halex reaction on DCNB at 130°C (refs. 65 - 67). However, a synergistic effect is observed when combining these two catalysts (Table 22). 

Where the catalyst is less nucleophilic, e.g. potassium fluoride or solid caesium fluoride, only one fluoride ion is likely to coordinate at all firmly to the silane. The nucleophilic reactant will then also be able to coordinate to the electrophilic silicon atom, itself receiving further activation in the process, and reaction ensues by intramolecular transfer about the hexacoordinate silicon atom as demonstrated in the GTP process. Less nucleophilic substrates such as alkyl halides are unreactive in these circumstances. 

Buchwald and co-workers successfully developed a catalytic fluorination of aryl triflates in 2009 using [(cinnamyl)PdCl]2 as the catalyst, f-BuBrettPhos (LI), a bullq biaiylphosphine ligand, and caesium fluoride as the fluoride salt. The success of this coupling relied on the formation of a reactive monomeric 14-electron intermediate 5, which was susceptible to reductive... 

Preparation.— Two procedures for the production of ethers from alky] halides have been mentioned earlier in this Report. From a study of fluoride salts on alumina as reagents for the alkylation of phenols and alcohols, potassium or caesium fluoride on alumina, in acetonitrile or 1,2-dimethoxyethane as the solvent, has been found to be the best combination for general use. A recently reported one-pot synthesis of phenyl ethers from phenol acetates involves their treatment, in solution in acetone, first with potassium carbonate and then with an alkyl halide. Another interesting new procedure for the alkylation of phenols utilizes the gas-liquid phase-transfer catalysis technique that was discussed above. In this case a phenol (or a thiophenol) and an alkyl halide, both gaseous, are passed through a bed of solid K2CO3 (or NaHCOs) at 170°C in the presence of a PEG e,g. Carbowax 6000) as the catalyst. ... 

Studies on the well known reaction between fluorine and carbon monoxide have revealed that a film of silver fluoride(s) on copper truly is a catalyst for the reaction Fj + CO - COFa, and for subsequent changes producing bistrifluoromethyl peroxide and trifluoromethyl hypofluorite, whereas caesium fluoride is not and since neither copper nor silver iluoride(s) appears to be a good catalyst for the reaction CF3 OF + COFj CFa O O CFg, it has been suggested that the fluorination of carbon monoxide or carbonyl fluoride in the presence of silver difluoride may possibly involve the steps... 

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