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Trifluoromethyl zinc compounds

Ligand exchange reactions can be used to prepare perfluoroalkylzinc compounds Solvated trifluoromethylzinc compounds can be synthesized via the reaction of dialkylzincs with bis(trifluoromethyl)mercury [36] (equation 27) A similar exchange process with bis(trif]uorometliyl)cadinium and diraethylzinc gives a mixture of tnfluoromethylcadmium and zinc compounds [77]... [Pg.676]

Since Cd(CF3)2DME is ordinarily vastly superior to Hg(CF3)2 as a tii-fluoromethylating agent, it seems only reasonable to assume that trifluoromethyl zinc compounds might well be even more effective. Diligand Zn(CF3)2 complexes have been prepared by a number of routes, including the reactions of Zn(CH3)2 with Hg(CF3)2 (87) orCF3I (88) in basic solvents like pyridine, dimethoxyethane, and acetonitrile. [Pg.233]

The less stable trifluoromethyl zinc compounds [48] can be used as a source of nucleophilic trifluoromethyl fragments either in the isolated form or generated in situ by sonication of perfluoroalkyl iodides with zinc in DMF or THF. Zinc perfluoroorganyls find application in Barbier-type reactions [49], palladium-catalyzed cross-coupling reactions [50], or hydroperfluoroalkylations of acetylenes or olefins [51] (Scheme 2.119). [Pg.106]

Very. similar behaviour has been reported [292] when zinc atoms are co-condensed with a number of fluoroalkyl iodides at —196°C, the zinc atom inserting into the carbon—iodine bond. The resultant non-solvated fluoro-organic zinc compounds have properties vastly different from those generated by conventional solution-phase techniques, being much more reactive and less stable. It was also shown that methyl iodide and trifluoromethyl bromide are much less reactive towards zinc atoms than is trifluoromethyl iodide. [Pg.229]

In similar work, CF3CCI2CO2CH3 yields methyl a-trifluoromethyl-a,(i-un-saturated carboxylates when reacted with a zinc-copper couple, aldehydes, and acetic anhydride [67] (equation 55). This methodology gives (Z)-a-fluoro-a- -un-saturated carboxylates from the reaction of carbonyl compounds with CFCI2CO2CH3 and zinc and acetic anhydride [6 ]. [Pg.683]

Replacement of the hydroxamic acid moiety of SAHA by an alternative chelator has been the subject of several studies. Suzuki and Miyata et al. have shown that replacement of the hydroxamic acid of SAHA with a free thiol moiety does not affect the enzymatic HDAC inhibition capability of the compound [57]. Furthermore, replacement of the hydroxamic acid of SAHA by a trifluoromethyl ketone was investigated by Frey et al. (Fig. 8) [58]. The activated ketone is readily hydrated to form the vicinal diol, a structural feature known to bind to zinc-dependent proteases [59]. The in vitro evaluation was done on a partially purified HDAC preparation consisting largely of HDAC 1 and HDAC2 [60], exhibiting an IC50 of 6.7 xM. [Pg.306]

Only the trifluoromethyl group has been subjected to reduction in this class of compound. Although not reduced by zinc in acetic acid or by sodium in ethanol, diethyl 2-methyl-4-(tri-fluoromethyl)-1//-pyrrole-3,5-dicarboxylate (1) is reduced at the trifluoromethyl group with an excess of lithium aluminum hydride to give the corresponding tetramethyl derivative 2 sodium borohydridc in ethanol is quite inefficient.104... [Pg.337]

Two aspects of ligand-exchange reactions are under active study at present. The first of these areas is the development of the chemistry of the bis(trifluoromethyl)zinc adducts. Like the cadmium compound, (CF3)2Zn is isolatable only if complexed by 2 mol of base. The (CF3)2Zn 2 pyridine species (101), however, exchanges ligands only at a sluggish rate (113). The adducts of the less basic solvents examined to date yield complexes that are exceedingly reactive but very difficult to purify. [Pg.312]

With certain 4,4-bis(trifluoromethyl)-3-aza-l-oxabutadienes this transformation can be achieved on heating with metals (91CZ253), especially zinc (89CHE1418) or with zinc/ultrasound (91CZ253). The fluorine atom at C—5 can be readily replaced by various nucleophiles (88S194). Via this route, 4-trifluoromethyl-l,3-oxazoles, -1,3-thiazoles, and -imidazoles can be introduced into many compounds of biological interest (Scheme 85). [Pg.42]

Trifluoromethylation of pyrrole (and indole and imidazole) occurs on irradiation of a mixture of the compound with difluorodiiodomethane, again via a SET mechanism involving fragmentation of the radical anion (Scheme 31). The presence of the CF3 group in the final products, 45 and 46, is a result either of secondary decomposition of the initially formed—but not isolated—difluoroiodomethyl derivatives, or of formation of the CF3 anion or radical in situ [94], Perfluoroalkyla-tion of pyrroles can also be achieved by an SrnI mechanism—by reaction with perfluoroalkyl iodides in the presence of magnesium or zinc [95]. Indole, on the other hand, gives a mixture of the seven possible alkylated derivatives when irradiated in the presence of ethyl chloroacetate [96],... [Pg.1023]

Bis[trifluoromethyl] tellurium and bis[pentafluorophenyl] tellurium react with dimethyl zinc or dimethyl eadmium with stepwise replacement of the perfluoroorganyl groups by methyl groups These reactions were carried out in trichloroliluoromethane in the presenee of bis[2-ethoxyethyl] ether as the complexing agent for the perfluoroorgano element compounds. ... [Pg.441]

Other electron-rich aromatic compounds can be employed as substrates. Pyrroles were trifluoromethylated regioselectively at the 2-position (ref. 27). Recently, the system trifluoromethyl iodide-zinc-sulfur dioxide in DMF at low temperature was used for the trifluoromethylation of aminonaphtalenes and aminoquinolines (ref. 28). Computational results support the mechanism in which the electrophilic trifluoromethyl radical intertact with the aromatic ring at the sites with the greatest electron density of the HOMO orbitals. [Pg.322]

Experiments were performed with various sulfoxylate radical anion precursors sodium dithionite, sodium hydroxymethanesulfinate or a mixture of sulfur dioxide with a reductant, such as zinc or sodium formate (refs. 29, 30).In contradistinction with the trifluoromethylation of aromatic compounds (Figs. 19,20), a stoiechiometric amount of the sulfoxylate radical anion precursor was necessary. In the disulfide case, there is no intermediate able to reduce back the sulfur dioxide which is formed in the medium (Fig. 22). [Pg.322]

For many years now, the reactivity of trifluoromethyl bromide has been underestimated. During the past decade the major breakthrough in this area has been the realisation that trifluoromethylation of organic compounds with this halide can be induced by mild reductants such as thiolates, zinc or sulfoxylate radical anion. Nowadays, a great variety of fluorinated products are available by these new methods sodium triflinate and triflic acid, trifluoromethylated alcohols, trifluoromethyl-containing aromatic compounds, ethyl trifluoropyruvate, trifluoromethylsulfides. ... [Pg.323]

The reduction of 5-(trifluoromethyl)dithiatriazine 6a with zinc dust in liquid sulfur dioxide at room temperature gives the five-membered radical 7 in 26% yield. At 0 °C the same procedure gives the 1,3,2,4,6-dithiatriazine oligomer.20 The 1,3-dibromo compound 6b decomposes to radical 7 with elimination of bromine and nitrogen.14... [Pg.850]

In contrast to (Ph2Zn)2, both bis(pentafluorophenyl)zinc and bis[2,4,6-tris(trifluoromethyl)phenyl]zinc have a two-coordinate monomeric solid-state structure approaching linearity, which is certainly a result of electronic and steric (see Steric Effect) properties of the orffto substituents (Figured). In the crystal structure of both compounds, the aromatic rings are almost orthogonal to one another. This special situation alleviates intramolecular (see Intramolecular) steric interactions and allows intramolecular stacking interactions between rings on adjacent molecules. [Pg.5204]

Cyclization of difunctional compounds is illustrated by the acyloin condensation of diesters (Fig. 19), conventionally performed with sodium in refluxing solvents, and improved by the presence of trimethylchlorosilane. A practical improvement was made with the use of technical-grade TMSCl and ultrasonically dispersed sodium.Thus, the reaction occurs at 0°C in 0.5 to 3 h. An experimental description is given in Ch. 9, p. 331. A chiral center at the a-position of the carbonyl does not suffer racemization. With p-halo esters, cyclizations lead to cyclopropyl derivatives in high yields, except with sterically hindered substrates. A similar reaction occurs with zinc and oxazabutadienes substituted by trifluoromethyl groups, with a fluoride ion as the leaving group (Eq. 15).ii ... [Pg.190]

Soon after its first application [29] (see p. 90 in this Section) it was found that the trifluoromethylation of carbonyl compounds was readily accomplished by the a one-pot reaction of iodotrifluoromethane, zinc and a carbonyl compound in DMF or THF at room temperature [58b]. [Pg.103]

Zinc in Barbier-Type Reactions Table 3.15. Trifluoromethylation of Carbonyl Compounds [78], [79]... [Pg.109]

Babu et al. reported that 3-acetoxy-4,4,4-trifluoro-2-butenoates (54) undergo self-condensation at 100 °C in presence of catalytic amounts of zinc chloride to yield 2,6-bis(trifluoromethyl)-4-pyrones 55. These compounds were further converted to the corresponding pyridine derivatives 56 via ammonolysis [24] (Scheme 17). [Pg.220]


See other pages where Trifluoromethyl zinc compounds is mentioned: [Pg.233]    [Pg.233]    [Pg.206]    [Pg.208]    [Pg.974]    [Pg.317]    [Pg.240]    [Pg.146]    [Pg.5205]    [Pg.136]    [Pg.9]    [Pg.973]    [Pg.224]    [Pg.582]    [Pg.268]    [Pg.181]    [Pg.118]    [Pg.324]    [Pg.9]    [Pg.140]   
See also in sourсe #XX -- [ Pg.152 ]




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