Trifluoromethane sulfonate complexes

Metal mediated reactions play an important role in organic chemistry. It has recently been found that rare earth trifluoromethane sulfonate complexes may be substituted for conventional Lewis acids in a variety of organic reactions. 

Bruce, D.W. and Hudson, S.A. (1994) Mesomorphic complexes of silver trifluoromethane sulfonate and silver dodecylsulfate with 2- and 3-fluoro-4-alkoxy-4-stilbazoles. Journal of Materials Chemistry, 4, 479-486. 

To [Co(en)2((S)-GluOBzl)]I2 (5.0 g, 7.3 X 10 3 mol) in dry trimethyl-phosphate (18 ml, 4A sieves) contained in a conical flask equipped with a drying tube was added methyl trifluoromethane sulfonate (8.0 g, 4.9 x 10 2 mol) and the mixture was stirred at room temperature for 30 min (Caution The alkylating agent is believed to be extremely toxic. Use a hood and avoid skin and vapor contact). The deep orange solution was then slowly poured into rapidly stirred dry ether (600 ml) and the precipitated semisolid recovered by decantation. The residue was dissolved in the minimum volume of dry methanol (10-20 ml), the product reprecipitated using further dry ether (400 ml), and the solid recovered as before. A further precipitation using methanol (10-20 ml) and dry ether (800 ml) produced the complex as a finely divided solid. This was recovered by filtration (porosity 4 sin-... 

Since one or more of the interactions in these systems might originate from the stationary phase, only a two- or a one-point interaction between the solute and the selector is necessary for mechanisms (2) and (3) to occur [50]. However, some of the CMPAs used in HPLC [37,40,51,52] have also been used as chiral selectors in CE [53-56], which indicates that at least one of the separation mechanisms between the selector and enantiomers is selective complex formation in the mobile phase in these cases, since there is no stationary phase present in CE. A recent example by Yuan et al. [57] is presented in Eigure 17.1. The authors introduced the use of (R)-A,A,A-trimethyl-2-aminobutanol-bis(trifluoromethane-sulfon)imidate as the chiral selector for enantioseparation in HPLC, CE, and GC. This chiral liquid serves simultaneously as a chiral selector and a co-solvent. 

Cyclocondensations of NADH analogues with / ara-benzoquinone are described in [368, 369]. For example, upon addition of dihydropyridine 338 to an acetonitrile solution of 339 in the presence of scandium trifluoromethane-sulfonate, the cycloaddition reaction occurs efficiently at room temperature, yielding cycloadduct 340 [368] (Scheme 3.113). This reaction passes via formation of a complex between azine and scandium trifluoromethanesulfonate. 

The synthetic plan in Figure 6 has been realized as full steps shown in Figure 7. C-Glycosidation of 18 with phenylthiotrimethylsilyl-acetylene and boron trifluoride etherate followed by treatment with biscobaltoctacarbonyl gave the biscobalthexacarbonyl complex 25 in 92% yield. Epimerization of the cobalt complex 25 was achieved with trifluoromethane sulfonic acid in... 

Against this background it is important that—quite fitting in this still new millennium— the first catalytic Friedel-Crafts acylations of (still relatively electron-rich) aromatic compounds were reported (Figure 5.35). Trifluoromethane sulfonates ( triflates ) of rare-earth metals, e. g., scandium(III)triflate, accomplish Friedel-Crafts acylations with amounts of as little as 1 mole percent. Something similar is true of the tris(trifluoromethanesulfonyl)-methides ( triflides ) of rare-earth metals. Unlike conventional Lewis acids, the cited rare-earth metal salts can form 1 1 complexes with the ketone produced, but these are so unstable that the Lewis acid can re-enter the reaction. Whether this works analogously for the third catalytic system of Figure 5.35 is unclear. 

Trifluoromethane sulfonate salts of lanthanides are used as starting materials for the preparation of other lanthanide complexes instead of perchlorates for safety reasons. 

Preparative Methods a solution of [Rh(nbd)acac] in THF is treated with fluoroboric acid, followed by addition of l,4-bis(diphenylphosphino)butane (dppb). The solution becomes deep red and ether is added to precipitate the catalyst, which is then isolated by filtration. The unpurified product is generally adequately pure for most applications. Recrystallization from methanol can be performed to obtain orange needles of [Rh(nbd)(dppb)]BF4. Although air-sensitive in solution, the crystalline complex is indefinitely stable when prepared pure and stored under N2 or Ar below 0 °C. A convenient preparation of the corresponding trifluoromethane-sulfonate has been described. The cyclooctadiene (cod) analog has been characterized by X-ray crystallography, ... 

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