Triflic acid addition

Pivaloyl chloride (24.2 g, 0.2 mol) and tert-hwiy alcohol (3.7 g, 0.05 mol) were combined and the mixture was heated to 85 °C. Triflic acid (15 g, 0.1 mol) was added over a period of 15 min. After the triflic acid addition was completed the mixture was stirred for an additional 10 min at 85 °C. The light brown reaction mixture was then cooled in an ice bath and poured into 100 mL of cold ethyl ether. The light tan precipitate was collected by filtration and air dried to give 9.6 g (54%) of pyrylium salt that was used without further purification in the next step. [Note The pyrylium trifluoromethanesulfonate salt does not have the explosive hazard of the corresponding perchlorate]... 

Scheme 30 Triflic acid addition to trans— [Cr(N2)2(P 4N 4)] yieids [N2H5] and [NH4...

The use of the enolsilyl ether of 1-menthone [16, 19, 21-23] and of some free triflic acid favors the formation of the thermodynamically controlled products as with free 2,2 -dihydroxydiphenyl [22] and only subsequently added HMDS 2 [22]. On reacting silylated alcohols and carbonyl compounds with pure trimethylsilyl triflate 20 under strictly anhydrous conditions no conversion to acetals is observed [24]. Apparently, only addition of minor amounts of humidity to hydrolyze TMSOTf 20 to the much stronger free triflic acid and hexamethyldisiloxane 7 or addition of traces of free triflic acid [18-21, 24, 26] or HCIO4 [25] leads to formation of acetals. 

Heating of hexane-2,5-dione 1487 with TCS 14, Nal, and triethylamine for 36 h, to form 1488, followed by addition of triflic acid and heating to 140 °C affords, on distillation, a mixture of 2,5-dimethylfuran 1489 and HMDSO 7 containing 90%... 

Choi and Sakakura et al. reported that iron(III) triflate, in situ formed from FeCls and triflic acid, efficiently catalyzes the intermolecular addition of carboxylic acids to various alkenes to yield carboxylic esters. The reaction is applicable to the synthesis of unstable esters, such as acrylates (Scheme 40) [50]. 

We found a new route for preparing larger amounts of these disilanes. The stepwise substitution of the phenyl groups at the silicon atoms with triflic acid and the additional conversion to Si-H and Si-C1 functions at low temperatures leads to pure chloro-hydrogen disilanes. The synthetic routes to 1,1,1-trichlorodisilane 2 and 1,1-dichlorodisilane 3 [7] are shown in Eq.(4). 

A potentially useful variant of the synthesis of some Mo(CHR)(NAr)(OR )2 complexes (R=CMe3 or CMe2Ph) consists of addition of two equivalents of a relatively acidic alcohol (R OH=a fluorinated alcohol or phenol) to Mo(NAr)(N-t-Bu)(CH2R)2 [78,79], a variation of the reaction of that type that was first reported in 1989 [80]. The more basic t-butylimido ligand is protonated selectively. This synthesis avoids the addition of triflic acid to Mo(NAr)2(CH2R)2 to give Mo(CHR)(N-t-Bu)(triflate)2(dimethoxyethane), the universal precursor to any Mo(CHR)(NAr)(OR )2 complex. Unfortunately, the method does not appear to succeed when R OH does not have a relatively high pK,. 

The suitability of ethers derived from 1,4-dihydroxy-1,2,3,4-tetrahydro-naphthalene (DHTN) in the design of polymers susceptible to catalyzed thermolytic cleavage is demonstrated by the behavior of its bis-p-nitrophenyl ether derivative upon treatment by a trace of acid. Figure 2, curve A, shows the H-NMR spectrum of the starting compound, while curve B shows the product which is obtained upon addition of triflic acid. It is readily seen from these spectra that quantitative cleavage into naphthalene and p-nitrophenol is obtained as elimination occurs easily to afford the aromatic product. The driving force in this reaction is the facile aroma-tization which produces naphthalene. 

Peroxytriflic acid (CF3SO4H) is prepared in situ from the addition of 90-98 % hydrogen peroxide to an excess of triflic acid. Peroxytriflic acid was first reported by Nielsen and co-workers and is possibly the most powerful peroxyacid known. The full potential of peroxytriflic acid has not been explored but it is reported to oxidize the weakly basic amine 2,3,4,5,6-pentanitroaniline (31) to hexanitrobenzene (55) in 90 % yield peroxydisulfuric acid achieves the same conversion in only 58 % yield. ... 

The reaction of dicyclohexylborane and trifluoromethanesulfonic acid is highly exothermic. On one occasion, the checkers cooled the reaction in an ice bath during the addition period, with no effect on product yield. The submitter reports that he once experienced a sudden vigorous reaction under cooling conditions, probably due to accumulation of unreacted triflic acid. It thus appears safer to add the acid at room temperature, slowly, so that it reacts immediately. 

Photoinduced oxidation of Cjq has been achieved by electron transfer from excited to a strong electron acceptor such as p-chloranil [72, 73], p-benzoquinone [73], tetracyano-p-quinodimethane (TCNQ) or tetracyanoethylene (TONE). This electron transfer proceeds efficiently only by addition of promoters such as Sc(OTf)3 or triflic acid, both of which strongly enhance the electron-transfer process [72, 73]. Another possibility to produce the cation is the electron transfer from to the singlet excited state of a strong electron acceptor such as N-methylacridinium hexafluorophosphate (NMA ) [74, 75], triphenylpyriliumtetrafluoroborate (TPP" )... 

Flectrophilic addition of polychloroalkanes such as, e.g., chloroform or 1,1,2,2-tetrachloroethane to Cjq with AICI3 in a 100-fold excess gives the monoadduct with a 1,4-addition pattern (Scheme 8.12) [93, 94], The reaction proceeds via a CjqR cation (19, Scheme 8.12) that is stabilized by the coordination of a chlorine atom to the cationic center. The cation is trapped by Cl to give the product 20. The chloroalkyl fullerenes can be readily hydrolyzed to form the corresponding fullerenol 21. This fullerenol can be utilized as a proper precursor for the cation, which is easily obtained by adding triflic acid. The stability of CjqR is similar to tertiary alkyl cations such as the tert-butyl-cation [95],... 

In earher work, the Hall group found that catalytic amounts of triflic acid promoted the addition of aUylboronates to aldehydes [132], While aUylboration reactions catalyzed by chiral Lewis acids in general led to only low levels of enan-tioselection [133], Hall found that chiral LBA 1 catalyzes the asymmetric addition of allyl- and crotylboronates to various aldehydes to provide products in excellent yields and moderate to high ee s (Scheme 5.71) [134]. Further, double diastereose-lective crotylboration could also be achieved with high selectivities using the... 

Kinetic studies of diallyltosylamide RCM reaction monitored by NMR and UV/VIS spectroscopy showed that thermal activation of the catalyst precursors la and Ib (25-80 °C) led to the in situ formation of a new species which could not be identified but appeared to be the active catalytic species [52]. Attempts to identify this thermally generated species were made in parallel by protonation of the catalysts I. Indeed, the protonation of allenylidene-ruthenium complex la by HBF4 revealed a significant increase in catalyst activity in the RCM reaction [31,32]. The influence of the addition of triflic acid to catalyst Ib in the ROMP of cyclooctene at room temperature (Table 8.2, entries 1,3) was even more dramatic. For a cyclooctene/ruthenium ratio of 1000 the TOF of ROMP with Ib was 1 min and with Ib and Sequiv. of TfOH it reached 950min [33]. 

The submitter obtained a colorless solution of boron triflate, but the checkers observed development of a yellow-orange color upon addition of triflic acid. Regardless of the color, the triflate solution could be used without a decrease in yields. 

The same reaction, but in the presence of triflic acid, results in /i-acetamido selenides by a mv-addition. In the case of a terminal olefin, the phenylseleno group is introduced mainly at the terminal carbon atom.13... 

Sterically hindered alkenes can be hydrogenated at —50°C using triflic acid and a hydride donor.483 In addition to Et3SiH, transition-metal carbonyl hydrides such as HM(CO)3Cp (M = W, Mo, Os) and HMn(CO)5 (M = Mn, Re) are suitable hydride donors. Alkenes that form tertiary carbocation on protonation are hydrogenated in high yields (90-100%), whereas yields for styrenes are lower (50-60%). Alkynes are converted to the corresponding saturated hydrocarbon by using HW(CO)3Cp in combination with triflic acid.484... 

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