Fluorides as catalysts

With Formaldehyde. The sulfuric acid cataly2ed reaction of formaldehyde [50-00-0] with carbon monoxide and water to glycoHc acid [79-14-1] at 473 K and 70 MPa (700 atm) pressure was the first step in an early process to manufacture ethylene glycol [107-21-1]. A patent (58) has described the use of Hquid hydrogen fluoride as catalyst, enabling the reaction to be carried out at 298 K and 7 MPa (70 atm) (eq. 18). 

Chlorination and bromination of perfluoroketimines take place only in the presence of alkali fluorides as catalyst [267] Chlorine fluoride adds readily across the CO or CN bond of polyfluonnated ketones and immes [268, 269]... 

TPB is produced by the reaction of tetrapropylene (see page 65) with benzene in the presence of aluminum chloride or hydrogen fluoride as catalyst. The reaction conditions for both catalysts differ insignificantly from each other. 

Some early examples involving microwave-assisted solvent-free Sonogashira couplings using palladium powder doped on alumina/potassium fluoride as catalyst were described by Kabalka and coworkers (Scheme 4.4) [150], In addition, this novel catalytic system has been used in microwave-assisted solvent-free Sonogashira coupling-cyclization of ortho-iodophenol with terminal alkynes, and similarly of ortho-ethynylphenols with aromatic iodides, to generate 2-substituted benzo[b]furans... 

Carbon disulfide gives an essentially quantitative yield of carbon tetrafluoride (4) and sulfur on reaction with sulfur tetrafluoride at 450 C in the presence of arsenic(III) fluoride as catalyst. At lower temperatures and with boron trifluoride as catalyst, bis(trifluoromethyl) polysulfides 5 and 6 are formed.205... 

The ring opening of several oxiranes by various thiosilanes (promoted by tetrabutylammonium fluoride as catalyst) occurs regioselectively under mild conditions.32 With the amphiphilic reagents isothiocyanatotrimethylsilane and O-trimethylsilyl thioacetate the sulfur centre exclusively attacks the oxiranes. A plausible reaction mechanism was suggested to explain the role of F as promoter. 

Thionyl fluoride can be prepared by the reaction of thio-nyl chloride with metal fluorides such as zinc(II) fluoride1 and arsenic (III) fluoride,2 and with metal fluorosulfites.3 It is also obtained by the action of hydrogen fluoride upon a mixture of tetrasulfur tetranitride and copper(II) oxide4 and by the reaction of hydrogen fluoride with thionyl chloride in the absence of6 or in the presence of6 antimony(V) fluoride as catalyst. Another method and the simplest on a laboratory scale involves the reaction of antimony(III) fluoride with thionyl chloride in the presence of antimony ) chloride as catalyst.7 This last procedure is described below. 

The first step is set up to produce hydrogen fluoride and the second yields trichlo-romethane (chloroform). Chloroform is then partially fluorinated with hydrogen fluoride to chlorodifluoromethane using antimony fluoride as catalyst in the third step. Finally, in the fourth step, chlorodifluoromethane is subjected to pyrolysis in which it is converted to tetrafluoroethylene. The pyrolysis is a noncatalytic gas-phase process carried out in a flow reactor at atmospheric or subatmospheric pressure and at temperatures 590 to 900°C (1094 to 1652°F) with yields as high as 95%. This last step is often conducted at the manufacturing site for PTFE because of the difficulty of handling the monomer.9... 

The use of hydrogen fluoride as catalyst is advantageous in many cases. Hydrogen fluoride can be prepared in situ by the addition of water to the reaction mixture. 

Table 5. Hydrofluorination of Halogenated Alkenes with Tantalum(V) Fluoride as Catalyst ...

Another possibility for the addition of fluorine to phenylacetylenes is fluorination with xenon difluoride in dichloromethane with anhydrous hydrogen fluoride as catalyst to give products... 

Rostamizadeh S, Ghaieni HR et al (2010) Clean one-pot synthesis of 1,2,4-oxadiazoles under solvent-free conditions using microwave irradiation and potassium fluoride as catalyst and solid support. Tetrahedron 66 494-497... 

The reaction mixture, which is calcined dolomite, ferrosilicon (75% Si) and 2% calcium fluoride as catalyst, is sealed into steel retorts which are evacuated to a pressure of about (2)10 5atm. On heating to 1180°C, the Mg pressure rises to about (5) 10-4 atm, and... 

More recently, the use of high pressure with tetra-n-butylammonium fluoride as catalyst allowed these reactions to be accomplished with cyclic ketones. Thus, the Henry reaction of nitroalkanes with 3- and 4-methylcyclohexanones in THF at 30 C and 9 kbar (1 bar = 100 kPa) afforded fair to high yields (60-90% after 4 d) of the corresponding nitro alcohols, while with 2-methyIcyclohexanones it was possible to obtain addition products, although in moderate yields. These facts explain the modest utility of the Henry reaction as a chain-lengthening reaction when the carbonyl component is a ketone, but also show the difference in reactivity of aldehyde and ketone C==0 groups with respect to nitromethane, primary and secondary nitroalkanes in the presence of a base as catalyst. Such a difference in reactivity can be considered as the most evident chemoselectivity of this reaction. 

Preparation of transition metal fluorides as catalysts for the environmentally sustainable HFC production. 

The oligomerisation process consists in anionic polymerisation of tetrafluoroethylcne in suitable aprotic solvents, e.g., diglyme or dimethylformamide, using KF, CsF or tetraalkylammonium fluoride as catalyst. The oligomerisation products are branched perfluoroolefins able to by further modified. Trimers, tetramers and pentamers of tetrafluoroethylene as well as dimers and trimers of hexafluoropropylene are useful essentially as a lyophobic backbone of fluorinated surfactants. This approach was initiated by ICI and Neos (Jap.), respectively. 

CFC s is supposed to deplete the ozone layer. This has led to a stepwise phase out of CFC s and other ozone depleting substances. Last years a number of destruction technologies have been proposed. For example CFC reacts with alcohol to yield carbon monoxide, carbon dioxide, methyl chloride and hydrogen fluoride. As catalyst a metal halide supported on activated carbon [18] is applied. In this way CFC-113 decomposes by reacting with methyl alcohol... 

The mechanism of anionic ring-opening polymerization of HFPO with alkali metal fluorides as catalyst was smdied by Kostjuk et al. [46] using F and H ID-NMR, and MALDI-TOF-MS spectroscopy. F NMR resonance assignments were made by comparing the changes in signal intensities for two different MWs and also by inspection of the chemical shifts for the different resonances. 

Albright, L.F. (1966) Modern chemical technology. VI. Alkylation processes using hydrogen fluoride as catalyst. Chem. Eng., 73, 205-210. 

Preparation by Fries rearrangement of 2-naphthyl propionate [7802] using hydrogen fluoride as catalyst [7803]. 

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