Arenes trifluoromethanesulfonate

A gold-catalysed alkylation of arenes with epoxides has also recently been discovered treating phenoxymethyloxiranes with AuCl3/3AgOTf (Tf = CF3SO2- triflate is trifluoromethanesulfonate i.e. OTf) (2.5 mol) in dichloromethane at 323 K yielded exclusively endo addition product 3-chromanols in good yield in 3h 37... 

The electrophilic, aromatic substitution of electron-rich arenes with the electron-deficient azodicarboxylate BTCEAD is a powerful method for the introduction, in a single operation, of a masked hydrazine or amino group.3 4 Several activators can be used for this amination reaction ZnCl2,4 BF3-Et20,4 LiCIO.4,3 and here, trifluoromethanesulfonic acid.5 Trifluoromethanesulfonic acid dramatically increases the rate of the amination reaction and makes possible the use of this methodology with poorly reactive substrates. 

Metal-catalyzed hydroarylation of alkynes catalyzed by electrophilic transition metal complexes has received much attention as a valuable synthetic alternative to the Heck and cross-coupling processes for the synthesis of alkenyl arenes (384). Metal trifluoromethanesulfonates (metal triflates) [M(OTQn M = Sc, Zr, In] catalyze the hydroarylation of alkynes via 71 complexation to give 1,1-diarylalkenes in very good yields (Scheme 32) (385). The reaction likely proceeds by a Friedel-Crafts mechanism via the alkenyl cation intermediate where the aryl starting material also serves as the solvent. 

Diaryl sulfones. Aryl sulfonyl bromides (but not sulfonyl chlorides) react with silver trifluoromethanesulfonate in nitromethane at 0° to form unstable mixed sulfonic anhydrides (c/ 4, 533-534). These react with arenes (threefold excess) at the same temperature to give diaryl sulfones usually in yields of 80-100%. 

Strong acids promote electrophilic hydroxylation of aromatics. Thus, sodium perborate - trifluoromethanesulfonic acid has been found to be a versatile reagent for the monohydroxylation of arenes to phenols [55b]. 

Ar2l+HS04, in several consecutive steps. Other inorganic iodosyl derivatives, such as iodosyl fluorosulfate (256) and iodosyl trifluoromethanesulfonate (258) also react with arenes or trimethylsilylarenes under mild conditions to afford the corresponding iodonium hydrosulfates 257 or triflates 259 (Scheme 2.73) [373,374],... 

Various unsymmetrically substituted diaryliodonium triflates 269 can be synthesized by the reaction of iodosylbenzene [380] or (diacetoxyiodo)arenes [381] with arenes in trifluoromethanesulfonic acid (Scheme 2.76). This simple procedure affords diaryliodonium triflates in relatively high yields, but it is limited to aromatic substrates that are not sensitive to strong acids. In a milder, more selective variation of this procedure (diacetoxyiodo)benzene is reacted with arylboronic acids in the presence of triflic acid at -30 °C to afford aryl(phenyl)iodonium triflates in 74-97% yields [377]. 

Reaction of phenol derivatives with acyl chlorides in acidic conditions may result in O-acylation or C-acylation, either directly or via a Fries rearrangement. Studies of acylations in acetonitrile using trifluoromethanesulfonic acid (trifllc acid) have shown that O-acylation is favoured at a low acid concentration, while a high acid concentration favours C-acylation. It has also been shown that A-hydroxysuccinimidyl and phenyl esters of benzoic acids are activated by triflic acid and can be used to acylate electron-rich arenes such as ferrocene or pyrene the reactive acylating intermediate is likely to be an acyl triflate or its protonated form. In a polyphosphoric acid medium, the rearrangement of 1,5- 1,8- and 9,10-diacetylanthracenes leads to the formation of the ring-closed product (56). DFT calculations support the conclusion that the reaction involves the intermediacy of 1,9-diacetylanthracene formed under kinetic rather than under thermodynamic control. ... 

Friedel-Crafts Reactions. Aluminum trifluoromethanesulfonate has been used for the Friedel-Crafts alkylation reaction of toluene with isopropyl and tert-butyl chlorides (eq 1), and for the acylation of benzene and toluene with acetyl and benzoyl chlorides in low to moderate yields. Intramolecular Friedel-Crafts acylation of an aromatic compound with Meldrum s acid has also been reported using catalytic amounts of Al(OTf)3. Acylation of 2-methoxynaphthalene with acetic anhydride has been reported using Al(OTf)3 and lithium perchlorate as an additive to afford the corresponding 6-acetylated adduct in 83% yield. Effective acylation of arenes with carboxylic acids has also been disclosed using polystyrene-supported Al(OTf)3. ... 

The addition of HN3 to nonactivated alkenes with formation of the saturated azides requires drastic conditions and a catalyst. Olefinic double bonds activated by conjugated, electron-withdrawing groups like -CN, -NO2, or -C(0)R react easily [8, 9]. The photolysis [10] and the pyrolysis [7] of HN3 with alkenes yields nitriles, N2, and decomposition products. The reaction of HN3 with alkines usually leads to 1,2,3-triazoles. Single or double addition with formation of vinyl azides or saturated diazides are rare [8, 9]. Arenes and HN3 form aniline derivatives directly and efficiently in the presence of trifluoroacetic acid and the strongly acidic trifluoromethanesulfonic acid [11]. The yield is frequently low in the presence ofH2S04[1]. 

---