Fluoroform, reaction

The same product is obtained from heptafluoropropyl methyl ketone [61]. The reaction resembles the fluoroform reaction of fluorinated alcohols [62] and ketones [63]. 

In the same way as a,a,(Z-trihalogenated carbonyl compounds are cleaved hydrolytically to produce haloforms, the fluorinated analogs also react by release of trifluoromethane. The fluoroform reaction has been described with aldehydes such as trifluoroacetaldehyde, alkyl trifluoromethyl ketones, and aryl trifluoromethyl ketones, e.g. l-(2,4-dihydroxyphcnyl)-... 

The fluoroform reaction has also been observed with higher perfluoroalkyl aldehydes and perfluoroalkyl ketones, which react with formation of l//-perfluoroalkanes and carboxylic acids. 

Depending on the ring substituent, trifluoromethoxyben2enes can be made by the sequential chlorination—fluorination of anisole(s) (351—354). A one-step process with commercial potential is the BF (or SbF2)-cataly2ed reaction of phenol with carbon tetrachloride/hydrogen fluoride (355). Aryl trifluoromethyl ethers, which may not be accessible by the above routes,may be made by fluorination of aryl fluoroformates or aryl chlorothioformates with sulfur tetrafluoride (348) or molybdenum hexafluoride (356). 

At 225—275°C, bromination of the vapor yields bromochloromethanes CCl Br, CCl2Br2, and CClBr. Chloroform reacts with aluminum bromide to form bromoform, CHBr. Chloroform cannot be direcdy fluorinated with elementary flourine fluoroform, CHF, is produced from chloroform by reaction with hydrogen fluoride in the presence of a metallic fluoride catalyst (8). It is also a coproduct of monochlorodifluoromethane from the HF—CHCl reaction over antimony chlorofluoride. Iodine gives a characteristic purple solution in chloroform but does not react even at the boiling point. Iodoform, CHI, may be produced from chloroform by reaction with ethyl iodide in the presence of aluminum chloride however, this is not the route normally used for its preparation. 

Fluoroform is brominated to yield bromotnfluoromethane The reaction rate and yield are both enhanced by vanous catalysts, as summanzed in Table 7 [2J, 24, 25]. 

Reactions that have led to other deoxyhalogeno sugars do not necessarily lead to deoxyfluoro sugars, as, for example, in the attempted decomposition of fluoroformates, the treatment of diazoketones and of 2-deoxy-2-diazohexonates with hydrogen fluoride, and the reaction of benzoxonium ions with halide ions. The reaction2281229 by which fluoroformates are thermally or catalytically decarbonylated to give alkyl fluorides has been applied to carbohydrates. Both thermal and catalytic treatment of 6-0-(fluoroformyl)-l,2 3,4-di-0-isopropylidene-... 

Goswami and Sarkar3 claimed to have prepared methyl and ethyl fluoroformates by the action of thallium fluoride on the corresponding chloroformates. These fluoroformates were described as powerful lacrimators. We found that no appreciable reaction took place between potassium fluoride and ethyl chloroformate in boiling carbon tetrachloride or nitrobenzene. Ethyl fluoroformate could, however, be readily produced by the action of potassium fluoride on ethyl chloroformate by using the autoclave technique. It was found not to have the lacrimatory properties claimed for it, and was non-toxic in comparison with M.F.A. This non-toxicity was to be expected, as the fluoroformate contains the COF and not the CH2F- group. 

Many solvent properties are related to density and vary with pressure in a SCF. These include the dielectric constant (er), the Hildebrand parameter (S) and n [5], The amount a parameter varies with pressure is different for each substance. So, for example, for scC02, which is very nonpolar, there is very little variation in the dielectric constant with pressure. However, the dielectric constants of both water and fluoroform vary considerably with pressure (Figure 6.3). This variation leads to the concept of tunable solvent parameters. If a property shows a strong pressure dependence, then it is possible to tune the parameter to that required for a particular process simply by altering the pressure [6], This may be useful in selectively extracting natural products or even in varying the chemical potential of reactants and catalysts in a reaction to alter the rate or product distributions of the reaction. 

The reaction of silyl enol ethers with fluoroformates and fluoroformamides, catalysed by the addition of tetra-n-butylammonium fluoride, produces enol carbonates and carbamates in acceptable yields [60],... 

Fluoroform (CHF3) efficiently trifluoromethylates aromatic aldehydes to the corresponding alcohols when deprotonated by potassium DMSylate in DMF. This is surprising, as species such as KCF3 have carbenoid character, and tend to be unstable. However, the reaction fails for solvents such as THF, and appears to depend on a highly specific role for DMF. It is proposed that CFs is trapped in situ by the solvent to form the gem-amino alcoholate (70), which acts as a stable, masked form of the anion, which then attacks the aldehyde, regenerating DMF. 

The iodine atom in the monoiodide may be replaced by other groups and, by reaction with silver salts, for example, As(CF3)2CN (b.p. 89 5°) and As(CFg)2SCN (b.p. 116—118°) are readily prepared. Reaction of the monoiodide with mercury gives the cacodyl As2(CF3)4 (b.p. 106 to 107°), while with mercuric oxide the oxide As2(CF3)40 (b.p. 95—97°) is formed. The chemistry of these substances has not yet been studied in detail, but it is noteworthy that hydrolysis of the perfluorocacodyl gives both fluoroform and fluoride, which parallels the observations made on the diphosphine. 

Fluorodisulfuric acid, salts of, 2 127 Fluoro(fluorosulfuryl) peroxide, 16 138-140 preparation of, 16 138, 139 properties of, 16 139 reactions of, 16 139, 140 Fluoroform, 3 379-380 Fluoroimines, preparation, 33 185 Fluorooximes, reaction with hexafluoroacetone, 30 271... 

Trifluoromethyl phenylsulfone is accessible from fluoroform and diphenyldisul-fide, and it has been proposed as a donor of CF3. However, the reaction must be performed in basic medium (f-BuOK) and is then limited to nonenolizable aldehydes and ketones. But it can also be used as a precursor of the Ruppert reagent. This latter... 

Both aromatic and aliphatic fluoroformates 7 can be readily prepared from phenols or alcohols and carbonyl difluoride and treated with sulfur tetrafluoride without isolation. Hydrogen fluoride evolved in the reaction of hydroxy compounds with carbonyl di fluoride serves as a catalyst for the consecutive reaction with sulfur tetrafluoride.15<)-162 This provides a general, convenient, direct synthesis of aryl and alkyl trifluoromethyl ethers 5 from phenols and alcohols. When the intermediate fluoroformate 7 is isolated prior to treatment with sulfur tetrafluoride, at least one mole equivalent of hydrogen fluoride is necessary to promote the fluorination reaction. 159 163 Representative examples of the conversion of hydroxy compounds 6 into trifluoromethyl ethers 5 via intermediate fluoroformates 7 are given (for other examples 7 -> 5, see Houben-Weyl, Vol. E4, pp 628. 629). 

Chloroalkyl carbonates do not undergo direct nucleophilic substitution with fluorine on heating with potassium fluoride either neat or in solution in the presence of 18-crown-6. They easily fragment to aldehydes and fluoroformates. This reaction has been exploited to synthesize valuable tertiary alkyl fluoroformates and benzyl fluoroformate. fert-Butyl fluoroformate (Boc-F) is a superior reagent for the preparation of Boc-amino acids.51... 

For slight variations in the workup procedure for some fluoroformates, see ref 51. With R = CC13 in the carbonate reactant 13, the reaction proceeds clearly without the 18-crown-6 catalyst, a variation most useful on a small industrial scale.51... 

There are some reactions in which boron trifluoride and boron trifluoride-diethyl ether complex are used as fluorinating agents, but they are not so frequently used and widespread. The best-known reaction is the decomposition of fluoroformates. In this type of reaction boron trifluoride or pyridine are essentially required as catalysts for the decomposition process. The formation of fluoroformates is established4 5 and the decomposition proceeds cither by heating in pyridine at higher temperature6 or by addition of boron trifluoride-diethyl ether complex at 0-50°C.7... 

Also unsuccessful have been all attempts to decarboxylate fluoroformates of various carbohydrates, but it has been shown that an excess of reagent, solvent, temperature and time of reaction are all of great importance in obtaining high yields for the fluorination of carbohydrate chloroformates (Table l).5... 

A number of imines have also been fluorinated. Typical reactions are the fluorination of N-(trifluoromethyl)difluoromethanimine (21) and 7V,7V,N -tris(trifluoromethyl)fluoroform-imidamide (22).103... 

Chlonne-36-labeled 1,1-dichlorotetrafluoroethane is produced photochemically from chlonne-36 and l-chloro-l,2,2,2-tetrafluoroethane in better than 90% yield [22] Fluoroform is brominated to yield bromotrifluoromethane The reaction rate and yield are both enhanced by various catalysts, as summarized in Table 7 [23, 24, 25]. 

Reactions of Organic Fluorine Compounds Table 7. Conversion of Fluoroform to Bromotrifluoromethane... 

S. C. Tucker, Solvent density inhomogeneities in supercritical fluids, Chem. Rev., 99 (1999) 391—418 O. Kajimoto, Solvation in supercritical fluids Its effects on energy transfer and chemical reactions, Chem. Rev., 99 (1999) 355-89 S. Nugent and B. M. Ladanyi, The effects of solute-solvent electrostatic interactions on solvatochromic shifts in supercritical C02, J. Chem. Phys., 120 (2004) 874-84 F. Ingrosso and B. M. Ladanyi, Solvation dynamics of C153 in supercritical fluoroform a simulation study based on two-site and five-site models of the solvent, J. Phys. Chem. B, 110 (2006) 10120-29 F. Ingrosso, B. M. Ladanyi, B. Mennucci and G. Scalmani, Solvation of coumarin 153 in supercritical fluoroform, J. Phys. Chem. B, 110 (2006) 4953-62 Y. Kimura and N. Hirota, Effect of solvent density and species on static and dynamic fluorescence Stokes shifts of coumarin 153, J. Chem. Phys., Ill (1999) 5474 ... 

There were not many new developments in the use of crown ethers for fluorination during the last decade, since the basicity of the fluoride anion is also enhanced along with the nucleophilicity. What is more, cheaper substitutes such as open-chain polyethers frequently led to similar results. However, there are still some reactions which are difficult to accomplish without these complexing agents and the synthesis of /-butyl fluoroformates... 

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