Power-variable trifluoromethylating agents, (trifluoromethyl)dibenzothio- and -selenophenium salt system

Aromatic and heterocyclic perfluoroalkyl sulfides. Methods of preparation

“…Dibenzoselenophenium triflate (A = Se, R 1 and R 2 = H) reacts much better with sodium dodecyl thiolate (yield of C 12 H 25 SCF 3 is 87%) than the sulfur analogue (yield 47%) [283–284]. …”

Shelf-stable electrophilic trifluoromethylating reagents: A brief historical perspective

“…(trifluoromethyl)dibenzoheterocyclic salts with electron-donating and electron-withdrawing substituents in benzene rings for fine tuning of their electrophilicity [12–14]. (Trifluoromethyl)dibenzothio- and selenophenium salts 5 and 6 , respectively, were synthesized either by oxidation of the starting sulfides (or selenides) with m -chloroperbenzoic acid followed by cyclization of the corresponding sulfoxides (or selenoxides) either with triflic anhydride or by direct fluorination with 10% F 2 /N 2 in the presence of one equivalent of triflic acid or HBF 4 (Scheme 2).…”

“…To increase the electrophilicity of salts 5 – 8 , the salts were nitrated with nitronium triflate generated in situ from nitric acid and triflic anhydride [12]. For example, mononitro-substituted thiophenium salt 9 was obtained after overnight stirring with nitronium triflate in nitromethane at room temperature, whereas treatment for 3 days in the absence of solvent gave the dinitro-substituted thiophenium salt 10 .…”

Trifluoromethylation of Arylsilanes with [(phen)CuCF3]

“…[5–11] We tested this reaction with PhSiMe(OSiMe 3 ) 2 (Ph-HMTS for phenyl heptamethyltrisiloxyl) because Ar-HMTS compounds can be formed by the silylation of aryl and heteroaryl C-H bonds. A range of common trifluoromethylation reagents, including both electrophilic CF 3 -sources (Togni’s reagent [21] and Umemoto’s reagent [22] ) and nucleophilic CF 3 -sources (Ruppert’s reagent [23] , Langlois’ reagent [24] , Chen’s reagent [25] , and (phen)CuCF 3 [26] ) (Scheme 1) were tested as the source of the CF 3 group.…”

“…To initiate our search for reagents and conditions which lead to the trifluoromethylation of arylsilanes,weinvestigated reaction conditions reported for the trifluoromethylation of arylboranates. [5][6][7][8][9][10][11] We tested this reaction with PhSiMe(OSiMe 3 ) 2 (Ph-HMTS for phenyl heptamethyltrisiloxane) because ArÀHMTS compounds can be formed by the silylation of aryl and heteroaryl CÀHb onds.Arange of common trifluoromethylation reagents,i ncluding both electrophilic CF 3 sources (Tognis reagent [21] and Umemotos reagent [22] )a nd nucleophilic CF 3 sources (Rupperts reagent, [23] Langlois reagent, [24] Chens reagent, [25] and [(phen)CuCF 3 ] [26] ;S cheme 1) were tested as the source of the CF 3 group.W ec onducted reactions with as eries of fluoride sources to activate the arylsilane by forming ahypervalent silicon species.The identity of the source of fluoride is likely to be crucial for the activation of the silane.T he fluoride must be sufficiently nucleophilic to add to the silicon, but it must not trigger rapid cleavage of the carbon-silicon bond. Most combinations of the sources of trifluoromethyl groups and fluoride we tested yielded either trace amounts or Scheme 1.…”