Boron Tris trifluoromethanesulfonate

The key of alkane transformation was assigned to the formation of CX3+-type cations that are electrophilic enough (probably due to a second complexation of A1X3), to abstract a hydride anion from linear and cycloalkanes. When these cations are generated in superacidic media, a protosolvation induces a superelectrophilic character, which was supported by Olah on the basis of high-level ab initio calculations 65 The generation of these cations was also used by various teams66,67 to initiate selective low temperature alkane activation. 

---

Boron tris(trifluoromethanesulfonate). This triflate is obtained by reaction of BC1, with triflic acid in S02C1F at -78°. Distillation at reduced pressure provides a solid, m. p. 45°, b. p. 68-73°/0.5 mm. It is extremely hygroscopic, and is soluble m CRiC, CHjNOi, CH CN. Aluminum and gallium triflate are poorly soluble in the common solvents. All three triflates can function as Friedel-Crafts catalysts, but the boron triflate is the most effective as a soluble catalyst. ... 

Lewis superacids, such as SbF5, AsF5, PF5, TaF5, NbF5, BF3, tris(pentafluoro-phenyl) borane, boron tris(trifluoromethanesulfonate), and aprotic organic superacids developed by Vol pin and co-workers. 

Boron tris (trifluoromethanesulfonate) was first prepared by Engelbrecht and Tschager in trifluoromethanesulfonic acid solution vide infra) as a conjugate acid system. Olah and co-workers have isolated B(OS02CF3)3 in pure form by treating boron trihalides (chlorides, bromides) with 3 equiv of triflic acid in Freon 113 or SO2CIF solution. 

Boron tris(trifluoromethanesulfonate) is a colorless low-melting compound [mp, 43-45°C bp, 68-73°C (0.5 Torr)] which decomposes on heating above 100°C at atmospheric pressure. It is extremely hygroscopic and is readily soluble in methylene chloride, 1,1,2-trifluorotrichloroethane (Freon 113), SO2, and SO2CIF Boron tris(trifluoromethanesulfonate) is a strong nonoxidizing Lewis acid and an efficient Friedel-Crafts catalyst. 

Preparation of Supersilylating Agents. TIPSCl reacts with boron tris(trifluoromethanesulfonate) or B(OTf)3 in CH2CI2 to form a so-called supersilylating agent with 1 1 stoichiometry (eq 18). ... 

Since it became obvious that liquid HF is not at all the detachment reagent of choice (see in contrast [35, p. 380]), the search for a similarly efficient reagent resulted recently in the utilization of boron tris (trifluoroacetate) [172], which in trifluoroacetic acid is reported to smoothly liberate peptides bound to the polymer support by benzyl ester type linkages. All above-mentioned protecting groups stable against trifluoroacetic acid are simultaneously cleavable. Trifluoromethanesulfonic acid [173] and pyridinium polyhydro-genfluoride are proposed for the same purpose [174] (Fig. 52). 

Some mild acidolytic cleavage methods have also been proposed. These include boron tris-(trifluoracetate) in TFA or CH2 CI2 (Pless and Bauer, 1973 Bauer and Pless, 1975). Another reagent, trifluoromethanesulfonic acid, may also prove as useful as HF for this purpose (Yajima and Kiso, 1974 Yajima et aL, 1974a). 

ALDOL CONDENSATION (+)-(R)-l-Amino-2- methoxymethyl)pyrrolidine. Boron trichloride. Dialkylboron tri-fluoromethanesulfonates. Dibenzyl-ammonium trifluoroacetate. Di- -butylboryl trifluoromethanesulfonate. Dichlorodiethylaminoborane. Diiso-propylaluminum phenoxide. Diisopropyl-aminomagnesium bromide. Lithium diisopropylamide. Morpholine-Camphoric acid. Proline. 

---