Gallium triflate

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. ... 

Benzothiazolines 72 are prepared by means of gallium(III) triflate mediated condensation of 2-aminobenzenethiol with fluorinated ketones followed by cyclization <07OL179>. Gallium triflate is a stable, water tolerant, recoverable, reusable, and environmentally friendly Lewis acid. Even when used in catalytic amounts, gallium triflate provides sufficient acidity required for the synthesis of fluorinated benzothiazolines. 

Metal triflates can be easily prepared from metal halides and triflic acid at -78 C. They show several unique properties compared with the corresponding metal halides. In an early study, Olah reported the use of boron-, aluminum-, and gallium triflates [M(OTf)J as effective Friedel-Crafts catalysts. In the benzoylation and acetylation of toluene and benzene with acyl chlorides, the relative reactivity is boron triflate > gallium triflate > aluminum triflate, in agreement with the relative acidity strength. 

Rare earth trifluoromethanesulfonates (triflates) are recently developed unique water tolerant and reusable Lewis acids. They may be used in aqueous solution to promote a wide range of organic transformations including C-C and C-heteroatom bond formation and cyclizations (38,39). Scandium trifkite exhibits increased catalytic activity and may be applied in similar transformations (40). Gallium triflate has also been found to be an equally useful catalyst (41). 

Although the Strecker reaction has been extensively studied with aldehydes using various kinds of catalysts and types of catalysis, the MC version nsing ketones has been less explored, maybe due to the less reactivity shown by these substrates, and only in 2007 it was reported the first efficient and extensively developed strategy using gallium triflate as catalyst (Scheme 10.25) [62]. 

Form Supplied in anhydrous gallium triflate is a white powder. 

Friedel-Crafts Alkylation and Acylation Reactions. Alcohols and alkyl halides react with aromatics in the presence of gallium triflate to give the corresponding alkylated products. Since Ga(OTf)3 does not decompose in the presence of water, alcohols can be used as good alkylating agents. Alkylation of benzene... 

Since acylated heteroaromatics are active intermediates for the synthesis of various pharmaceuticals, catalytic acylation of heteroaromatics using safe and reusable catalysts is important in pharmaceutical industry. It is found that gallium triflate can act as an efficient catalyst for Friedel-Crafts acylation of furan, pyrrole, and indole derivatives (eq 3-5). Friedel-Crafts acylation of acyl anilides using AICI3 requires a stoichiometric amount of the catalyst and the yields are low. Studies showed that catalytic acylation of aniline derivatives can be achieved in high yields using Ga(OTf)3 (10 mol%) in the presence of LiClOa (eq 6). ... 

Gallium triflate also catalyzes ring opening of epoxides by thiols with high regioselectivety and chemoselectivity. The reaction is highly catalytic (only 1 mol % gallium triflate is required) and occurs under solvent-free conditions (eqs 12 and 13). ... 

Epoxyolefin Cyclization. Among many metal triflates, gallium triflate is shown to be a highly effective catalyst for epoxyolefin cyclization. Geraniolene oxide undergoes isomerization and cyclization to yield a mixture of cyclized products as well as rearranged products (eq 15). Product composition is mainly influenced by the nature of the solvent and the substrate concentration. ... 

Synthesis of Benzimidazolines, Benzothiazolines, Benzoxa-zolines, and Dihydrobenzoxazinones. Benzimidazolines, benzothiazolines, benzoxazolines, and dihydrobenzoxazinones are inqiortant classes of heteroaromatics. One-pot synthesis of fluo-rinated benzimidazolines, benzothiazolines, benzoxazolines, and dihydrobenzoxazinones and their various derivatives can be easily achieved by the reaction of ketones with o-aminoarene derivatives using gallium triflate as a catalyst (eq 16). ... 

Thomas Mathew University of Southern California, Los Angeles, CA, USA GaUium(III) Trifluoromethanesulfonate (Gallium Triflate) 339... 

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