Sulfonium compounds trifluoromethyl

A wide range of nucleophilic substrates of different reactivity were trifluoromethylated with these reagents. The substrates include carbanions, activated aromatics, heteroaromatics, enol silyl ethers, enamines, phosphines, thiolate ions and iodide anions. " (Scheme 3.8) The least reactive substrates, such as triphenylphosphine, aniline and phenols, require the use of the most reactive dinitro derivative. Most of the reactions can be conveniently performed with the unsubstituted 5-trifluoromethyl dibenzothiophenium salt (35). The least reactive sulfonium salts are the acyclic sulfonium compounds which reacted only with the sodium thiolates.55,59... 

Interestingly, the trifluoromethyl oxonium compound is deshielded relative to the analogous ether, whereas those of the sulfonium CF3 groups are actually shielded compared to the simple sulfides. 

In the presence of tris(dimcthylamino)sulfonium difluorotrimethylsilicatc64 65 as a source of nonhydrated fluoride ion.66 trimethyl(trifluoromethyl)si]anc undergoes perfluoroalkylation of polyfluoroaromatic compounds.64 Fluorinated aromatic substrates such as perfluoropyridinc, perfluorotoluene, perfluorobenzonitrile, and perfluorobiphcnyl can be fluoroalkylated, but se-lcctivities are difficult to control and some multiple substitution takes place, resulting in modest yields of monoadducts 8 in the 30-50% range.64... 

The [Ru(bpy)3] photocatalyst was also applied in the following novel visible-light driven processes (i) synthesis of indazolo[2,3-a]quinoline derivatives from 2-(2-nitrophenyl)-l,2,3,4-tetra-hydroquinolines (ii) azido- and amino-trifluoromethylation of alkenes (iii) reduction of nitro compounds to oximes (iv) generation of aryl radicals by visible-light photocatalytic reduction of sulfonium salts. ... 

Reactions with Carbonyl Compounds. TMSCF3 reacts with aldehydes in the presence of a catalytic amount of tetra-w-butylammonium fluoride (TBAF) in THF to form the corresponding trifluoromethylated carbinols in good to excellent yields following aqueous hydrolysis of the silyl ethers (eq 3) 2.3.6,10 The reaction also works very well for ketones under the same conditions, with the exception of extremely hindered ones such as l,7,7-trimethylbicyclo[2.2.1]heptan-2-one, di-l-adamantyl ketone, and fenchone. The reaction has been characterized as a fluorideinduced autocatalytic reaction. Other initiators such as tris(dimethylamino)sulfonium difluorotrimethylsilicate (TASF), potassium fluoride, Ph3SnF2, andRO can also be used for these reactions. ForthereactionsofTMSCFs and perfluorinated ketones and pentafluorobenzaldehyde, excess of KF is needed. 

The 5 -(trifluoromethyl)sulfonium salt can be applied to copper-mediated trifluoromethylation. Trifluoromethylation of heteroaryl iodides with the sulfonium salt proceeds in presence of stoichiometric copper under mild condition (eqs 17 and 18). Boronic acids also react with sulfonium salt (eqs 19 and 20), though 1 equiv of NaHCOs is needed as the base. These reactions furnish corresponding trifluoromethylated products in high yield. The copper-mediated trifluoromethylation reaction advances not only with aromatic compounds, but also at a benzylic position (eq 21). Trifluoromethylation reaction of benzyl bromides with S -(trifluoromethyl) sulfonium salt provides (trifluoroethyl)arenes in high yields. 

Some articles have described synthesis of 3-trifluoromethylquinoline (271) [161-165]. Catalytic oxidative trifluoromethylation of 3-qunolineboronic acid (270) resulted in 3-trifluoromethylquinoline in 49 % yield [161]. Use Togni s reagent (272) in reaction with boronic acids 270 resulted in increase yield of 271 up to 53 % [162]. 3-Trifluoromethylquinoline was also obtained by reaction of boronic acids 270 with CF3I [163] or with trifluoromethyl sulfonium salts [164] in 87 % yield. Interaction of 3-iodoquinoline (273) with sodium trifluoromethyl formate at presence Cu and AgjO also led to compound 271 [165] (Scheme 80). 

Zhang C-P, Chen Q-Y, Xiao J-C, Wang Z-L, Zhang C-T, Gu Y-C (2011) Copper-mediated trifluoromethylation of heteroaromatic compounds by trifluoromethyl sulfonium salts. Angew Chem Int Ed 50 1896-1900... 

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