Trifluoromethyl reactions with halides

Alkylzinc halides have also been prepared under microwave irradiation. The Reformatsky reagents (2-t-butoxy-2-oxoethyl)zinc bromide and [(2-dibenzylamino)-2-oxoethyl]zinc bromide were synthesized from the corresponding bromides via reaction with zinc in THF (Scheme 5) [24], The oxidative addition was executed at 100 °C in 5 min. The obtained reagents were subsequently used in Negishi reactions on 2-bromopyridine, 3-bromopyridine, 2-bromo-5-nitropyridine, and 2-bromo-5-trifluoromethyl-pyridine using Pd(PPh3)4 as a catalyst (Scheme 5). 

G. Reactions of Trifluoromethyl Radicals with Organic Halides. 189... 

Although belonging to a slightly different class of reactions, the reaction of trifluoromethyl radicals with sulfur vapor has been shown to provide a route to trifluoromethyl polysulfide compounds (20). Instead of using sulfur halides, which undoubtedly would also give positive results, elemental sulfur (Ss) was vaporized and dissociated into atomic and polyatomic sulfur species. 

To date, however, only few reactions between phosphine and a non-metal halide, in which a chemical bond is formed between phosphorus and a non-metal by HCl condensation, are known. To these, apart from the above-mentioned reactions, belongs also the reaction with CF3SCI which, depending upon the chosen proportions of the reactants, in a sealed tube at -95 °C leads to the formation of (CF3S)2PH or (CF3S)3P Both compounds are not very stable thermally and decompose at 40-50 °C. Tris(trifluoromethylthio)-phosphine forms an unstable adduct with chlorine, which decomposes at 0 °C to give a mixture of PCI3, bis(trifluoromethyl)-disulphide and trifluoromethyl-sulphenyl chloride. 

Trifluoro-2-propenyl zinc reagent can undergo palladium-catalyzed cross-coupling reaction with aryl or vinyl halides [169,170], which provides a novel method for the introduction of the trifluoromethyl group into organic molecules (Scheme 59). The trifluoro analogue of Naproxen has been prepared by this method [169] (Scheme 60). 

The first long-lived fluorine-containing carbocation was discovered by Olah and coworkers.32 Thus, the fluorodimethylcarbcnium ion [Me2CF+] was obtained by protonation of 2-fluoropropene and also from 2,2-difluoropropane by reaction with antimony(V) fluoride. In the course of these investigations it was found that a-F stabilizes a cationic state, whereas fi-F is destabilizing. Attempts to prepare the simplest member of this class, the trifluoromethyl carbocation CF3+ failed. The ionization of trifluoromethyl halides with antimony(V) fluoride at — 80 C yielded only carbon tetrafluoride. 

The reaction of tris(trifluoromethyl)bismuthine with chlorine, bromine, or iodine, however, has been found to yield the corresponding bismuth trihalide and trifluoromethyl halide (61) ... 

The interpretation of reactivities here provides a particular challenge, because differences in solvation and bond energies contribute differently to reaction rates and equilibria. Analysis in terms of the Marcus equation, in which effects on reactivity arising from changes in intrinsic barrier and equilibrium constant can be separated, is an undoubted advantage. Only rather recently, however, have equilibrium constants, essential to a Marcus analysis, become available for reactions of halide ions with relatively stable carbocations, such as the trityl cation, the bis-trifluoromethyl quinone methide (49), and the rather less stable benzhydryl cations.19,219... 

Treatment of l-(/-butoxylcarbonyl)-2-(methoxycarbonylmethylene)-4-(trifluoromethyl)azetidine 28 with potassium bis(trimethylsilyl)amide at — 78 °C followed by reaction with an alkyl halide or an aldehyde afforded 3-alkyl-substituted azetidine derivatives 29 (Equation 6) <20030L4101>. This procedure is of particular importance to the synthesis of azetidines with an alkyl substituent at the C-3 position. 

The reaction of bis[trifluoromethyl] tellurium with chlorine fluoride at — 78° with fluorotrichloromethane as solvent first produced his[trifluoromethyl] tellurium chloride fluoride. When the reaction mixture was concentrated, the l9F-NMR signal of the chloride fluoride disappeared and was replaced by signals for bis[trifluoromethyl] tellurium difluoride and bis[trifluoromethyl] tellurium dichloride2. The diorgano tellurium dihalides reported in the literature as mixed dihalides might be mixtures of symmetrical dihalides. All mixed halide species were identified by 125Te- and 19F-NMR spectroscopy in dimethylformamide solutions prepared from equimolar amounts of two different tellurium dihalides3. 

Corrosion inhibitors, [1.2,4]triazino[4,3-ojbenzimidazoles, 59, 155 Coulson-Rushbrook theorem, 55, 273 Coumarins, see l-Benzopyran-2-ones Coupling reactions, trifluoromethyl iodide with aryl halides, 60, 12 Covalent hydration in 6-nitro-l 1,2,4]triazolo[ 1,5-a)-pyrimidines, 57, 107 of coordinated ligands, 58, 138 Creutz-Taube ion, 58, 124 Criss-cross cycloadditions, of... 

The cross-coupling reaction of alkenyl(fluoro)silanes with aryl halides sometimes produces, in addition to the desired ipso-cowpled products, small amounts of cmc-coupled products [14]. The czne-coupling is often striking in the reaction with organotin compounds. The isomer ratio of products produced by the reaction of l-fluoro(dimethyl)silyl-l-phenylethene with aryl iodides is found to depend on the electronic nature of a substituent on aryl iodides (Eq. 11) an electron-withdrawing group like trifluoromethyl and acetyl favors the formation of the ipso-coupled product. To explain the substituent effect, the mechanism depicted in Scheme 3 is proposed for the transmetalation of alkenylsilanes with palladium(ll) complexes. It is considered that an electron-donating substituent on Ar enhances... 

Perfluoroalkylcopper reagents are the most studied perfluoroalkyl organometallic reagents due to their unique combination of thermal stability and chemical reactivity. They are readily prepared by copper metal insertion reactions with perfluoroalkyl halides in a coordinating solvent (e.g., formation of decarboxylation reactions of perfluoroalkanoic acid salts and copper(I) halide (e.g., formation of 2 ), or metathesis reactions (e.g., formation of 4 via 3 ). (Trifluoro-methyl)copper (4) has also been recently accessed by decomposition of methyl 2,2-difluoro-2-(fluorosulfonyl)acetate (5) or methyl perfluoro [2-(fluorosulfonyl)ethoxy]acetate (6) in the presence of copper(I) iodide and by reaction of trimethyl(trifluoromethyl)silane (7) with fluoride and copper(I) iodide. ... 

The method is applicable for triorganoarsenic compounds bearing aryl or vinyl substituents (equations 76 , 77 and 78 ), while for the preparation of alkylarsenic halides this method has not been useful since only adduct formation and redox reactions have been reported between R3AS and AsXj (equations 79a and b) . Reaction of tris(trifluoromethyl) arsine with arsenic iodide, however, has been reported to afford a mixture of halides (equation 80) . In the reaction of unsymmetrically substituted compounds such as 4, cleavage of the aryl-arsenic bond is preferred to that of the alkyl-arsenic bond (equation 78 ). The cleavage of 4 by this method is in contrast to that of 3 in thermolysis (equation 75). 

The reaction of trifluoromethyl iodide with arene thiolates provides trifluoromethyl aryl sulfides via a single electron transfer (SET) reaction rather than the SN2 reaction, which is the only formal mechanism (Scheme 2.31). In general, perfluoroalkyl (Rf—X), ferf-alkyl, and vinyl and aromatic halides are strongly deactivated for the replacement of halogens with... 

Methylarsine, trifluoromethylarsine, and bis(trifluoromethyl)arsine [371-74-4], C2HAsF6, are gases at room temperature all other primary and secondary arsines are liquids or solids. These compounds are extremely sensitive to oxygen, and in some cases are spontaneously inflammable in air (45). They readily undergo addition reactions with alkenes (51), alkynes (52), aldehydes (qv) (53), ketones (qv) (54), isocyanates (55), and azo compounds (56). They also react with diborane (43) and a variety of other Lewis acids. Alkyl halides react with primary and secondary arsines to yield quaternary arsenic compounds (57). 

RX — RCF. Organic halides are converted into trifluoromethyl compounds by catalyzed reactions with ClCFjCOOMe or FS02(CF2)20CF2C00Me. ... 

Trifluoromethyl aryl sulfides. The preparation of these substances from aryl halides requires a Cu(I)-catalyzed reaction with sulfur and methyl fluorosulfonyldi-fluoroacetate in HMPA or A(-methylpyrrolidinone. 

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