Acids triflic

In the presence of strongly acidic media, such as triflic acid, hydrogen cyanide or trimethylsilyl cyanide formylates aromatics such as ben2ene. Diprotonotated nittiles were proposed as the active electrophilic species in these reactions (119). 

Bis (trimethyl silyl) peroxide (CH2)3SiOOSi(CH2)3 can be used with triflic acid (CF SO H) and acts as an effective hydroxylating agent of aromatics such as toluene, mesitylene and naphthalene (165). Sodium perborate (a safe and inexpensive commercial chemical) can be used in conjunction with the triflic acid to hydroxylate aromatics (166). 

Subsequently it was found that trimethylsilyl azide in triflic acid is a more efficient and improved reagent for aminations (169). Amination of toluene in the presence of trichloramine—A1 CL proceeds predominantly at the / -position. 

Petfluotoalkanesulfonic acids also show high acidity. The parent trifluoromethanesulfonic acid (triflic acid), CF SO H, is commercially prepared by electrochemical fluorination of methanesulfonic acid (214). It has an value of —14.1 (215,216). The higher homologues show slightly decreasing acidities. 

A direct, one-step aromatization of 19-substituted steroids has appeared in the Hterature, ie, cholesterol (3), dehydroisoandrosterone, androsterone, progesterone (1), and testosterone react with an electrophilic mthenium complex, C Ru , where Cp represents Tj -cyclopentadienyl, obtained through protonation of [Cp Ru(OCH2)]2 using triflic acid, to provide estrone (20) directly (46). 

Molecular examples of trivalent molybdenum are known in mononuclear, dinuclear, and tetranuclear complexes, as illustrated in Figure 5. The hexachloride ion, MoCk (Fig- 5a) is generated by the electrolysis of Mo(VI) in concentrated HCl. Hydrolysis of MoCP in acid gives the hexaaquamolybdenum(III) ion, Mo(H20) g, which is obtainable in solution of poorly coordinating acids, such as triflic acid (17). Several molybdenum(III) organometaUic compounds are known. These contain a single cyclopentadienyl ligand (Cp) attached to Mo (Fig. 5d) (27). 

The stmctural architecture of siUcone polymers, such as the number of D, T, and Q sites and the number and type of cross-link sites, can be deterrnined by a degradative analysis technique in which the polymer is allowed to react with a large excess of a capping agent, such as hexamethyidisiloxane, in the presence of a suitable equiUbration catalyst (eq. 38). Triflic acid is often used as a catalyst because it promotes the depolymerization process at ambient temperature (444). A related process employs the KOH- or KOC2H -catalyzed reaction of siUcones with excess Si(OC2H )4 (eq. 39) to produce ethoxylated methylsiUcon species, which are quantitatively deterrnined by gc (445). 

Trifluoromethanesulfonic acid, also known as triflic acid [1493-13-6] is widely used ia organic syntheses and has been thoroughly reviewed (93,94). It was first prepared ia 1954 via the oxidation of bis(trifluoromethylthio)mercury with hydrogen peroxide [7722-84-1] (95). Several other routes of preparation have been disclosed (96—98). The acid exhibits excellent thermal and hydrolytic stabiUty, it is not readily oxidized or reduced, nor is it prone to fluoride anion generation. 

Cupric trifluoromethylsulfonate (copper II triflate) [34946-82-2] M 361.7, pK <-3.0 (for triflic acid). Dissolve in MeCN, add dry Et20 until cloudy and cool at -20° in a freezer. The light blue ppte is collected and dried in a vacuum oven at 130°/20mm for 8h. It has Xmax 737nm (e 22.4M cm ) in AcOH. [J Am Chem Soc 95 330 1973], It has also been dried in a vessel at O.lTorr by heating with a Fischer burner [J Org Chem 43 3422 1978], It has been dried at 110-120°/5mm for Ih before use and forms a benzene complex which should be handled in a dry box because it is air sensitive [Chem Pharm Bull Jpn 28 262 I980-, J Am Chem Soc 95 330 1973]. 

Di-tcrt-butyl silyl bis(trifluoromethanesulfonate) [85272-31-7] M 440.5, b 73.5-74.5°/0.35mm, d 1.36 (see pK for triflic acid). Purified by fractional distillation. It is a pale yellow liquid which should be stored under argon. It is less reactive than the diisopropyl analogue. The presence of the intermediate monochloro compound can be detected by H NMR, (CHCI3) rer/-Bu2Si(OT02 [5 l -25s] but... 

Mixed anhydrides of a carboxylic acid and trifluoroacetic or triflic acids... 

Fluorinated sulflnates are prepared from sodium dithionite and liquid per-fluoroalkyl halides [74] (equation 67). For the transformation of the gaseous and poorly reactive trifluoromethyl bromide, it is necessary to use moderate pressure [75] (equation 68) These reactions are interpreted by a SET between the intermediate sulfur dioxide radical anion and the halide The sodium trifluorometh-anesulfinate thus obtained is an intermediate for a chemical synthesis of triflic acid. 

This simplified procedure gives the sulfonic acid in very good yield, however the same procedure is not applicable to the synthesis of triflic acid, which would require the synthesis of trifluoromethyllifhium. This procedure also is not applicable to the preparation of the sulfonic acids requiring the use of perfluoropropyl or isopropyllithium intermediates... 

Oxidation of the tnfluoromethanesulfinate gives triflic acid [50] (equation 43) Chlonnation of the perfluoroalkylsulfinates gives the corresponding perfluoroalkyl sulfonyl chlondes [5f] (equation 44)... 

In general, fluorinated sulfonic acids can be used as eatalysts for various cationic cyclizations Typical examples are the triflic acid catalysis in the double cyclization of A,VV-dibenzylpropynylamine [82] (equation 30) and the fluorosulfonic acid catalyzed condensation of phenylacetaldehyde [<5J] (equation 31)... 

Triflic acid is strong enough to protonate polycyclic saturated hydrocarbons [77, 78, 79], and even -butane [80, 81], and to initiate skeletal rearrangements Acidic treatment of homoadamantane [77] (equation 32), 2-homoprotoadamantane [78] (equation 33), or as 2,3-trimethylenebicyclo[3 3 Ojoctane [79] (equation 34) causes their rearrangement to isomenc hydrocarbons... 

The quantitative deprotection of phenol ethers can be achieved by the action of a catalytic amount of triflic acid in trifluoroethanol at -5 °C [86],... 

Trifluoromethanesulfonic (triflic) anhydride is commercially available or can be prepared easily by the reaction of triflic acid with phosphorus pentoxide [66] This moderately hygroscopic colorless liquid is a useful reagent for the preparation of various organic derivatives of triflic acid A large variety of organic ionic triflates can be prepared from triflic anhydride A recent example is the preparation of unusual oxo-bridged dicatiomc salts of different types [SS, 89, 90, 91, 92, 93] (equations 38-44) Stabilized dication ether salts of the Huckel aromatic system and some other systems (equations 38 and 39) can be prepared in one step by the... 

The chloride of triflic acid (trifluoromethanesulfonyl chloride) is an effective sulfonylating agent Like triflic anhydride, it usually reacts with alcohols and other nucleophiles with the formation of the corresponding derivatives of tnflic acid [69] However, in some reactions, it acts as a chlorinating reagent [98] The reactions of tnfluoromethanesulfonyl chloride with 1,3-dicarbonyl compounds or some carboxylic esters in the presence of a base result m the formation of chlonnated products in high yields (equation 49)... 

Trimethylsilyl trifluoromethanesulfonate (trimethylsilyl triflate) is the most synthetically useful representative of the family of trialkylsilyl perfluoroalkane-sulfonates (for a review, see reference 101) This reagent is commercially available or can be prepared easily by the reaction of chlorotrimethylsilane and triflic acid [101] It has wide application in organic synthesis as an excellent silylating reagent... 

A large variety of salts of triflic acid formed both from metals and nonmetals are known Many of these salts are versatile reagents for organic synthesis because of such properties of the tnflate anion as very low nucleophilicity and low coordinating ability However, despite low nucleophilicity, the triflate anion can combine with carbocationic intermediates under appropriate conditions to form triflate esters [116, 117, II8. ... 

Triflates of aluminum, gallium and boron, which are readily available by the reaction of the corresponding chlorides with triflic acid, are effective Fnedel-Crafis catalysis for alkylation and acylation of aromatic compounds [119, 120] Thus alkylation of toluene with various alkyl halides m the presence of these catalysts proceeds rapidly at room temperature 111 methylene chloride or ni-tromethane Favorable properties of the triflates in comparison with the correspond mg fluorides or chlorides are considerably decreased volatility and higher catalytic activity [120]... 

Silver(I) triflate is widely applied to the preparation of various derivatives of triflic acid, both covalent esters [66] and ionic salts For example, it can be used for the in situ generation of iodine([) triflate, a very effective lodinatmg reagent for aromatic and heteroaromatic compounds [130] (equations 65 and 66)... 

NaBH3CN, TiCl4, CH3CN, rt, 3 h, 83% yield. NaBH3CN, THF, ether/HCl converts a 4,6-benzylidene to a b-O-benzylpyranoside". The use of triflic acid improves this process because the stoichiometry is more conveniently controlled." ... 

The third group of reactions is termed C3-C5 tandem difunctionalization (96JA5672,98JA509). Protonation of 3 (X = O, R = R = R = H) with triflic acid in methanol causes ring opening and formation of the tmns-14 and d.s-4-methoxy-... 

JA5190, 940M5132). Proton abstraction from 109 gives a neutral ti C) 2-thienyl complex, 110. Such a reaction becomes impossible in case of the 2,5-dimethylthiophene analog of 109. However, use of a strong base such as potassium hydroxide in methanol gives 111. An attempted transformation of 109 to 110 by protonation with triflic acid leads, however, to the thienylcarbene complex cation 112 where the aromaticity is disrupted. 

JA5190). Upon deprotonation by bases, 285 (R = H) transforms to 286, and 285 (R = Me) goes to 287 because the C2 position is occupied. Protonation of 286 with triflic acid occurs at position 3 of the heteroring to form the benzothienyl carbene complex 288, and deprotonation reverts it to 286. This kind of process is a rarity for the uncomplexed benzothiophenes (81AHC171). 

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