Rearrangements bismuth triflate

We have previously reported that when the rearrangement of trans-stilbene oxide was carried out with CF3SO3H, the solution turned red and the product diphenylacetaldehyde was less pure than that obtained with bismuth triflate. This observation points to the role of bismuth(III) triflate as a Lewis acid in the rearrangement of epoxides and not to protic acid catalysis by triflic acid released by hydrolysis of bismuth triflate. 

Bhatia KA, Eash KJ, Leonard NM, Oswald MC, Mohan RS (2001) A facile and efficient method for the rearrangement of aryl-substituted epoxides to aldehydes and ketones using bismuth triflate. Tetrahedron Lett 42 8129-8132... 

Bismuth(III) triflate tetrahydrate can be utilized as a more commercially available catalyst for the Fries rearrangement of PAs to 2-hydrox-yaryl ketones. In the reaction with 1-naphthyl acetate, bismuth triflate (10% mol) gives the best yield in 2-acetyl-l-naphthol, the amount of... 

Ollevier, T, Desyroy V., Asim, M., and Brochu, M.-C. 2004. Bismuth triflate-catalyzed Fries rearrangement of aryl acetates. Synlett 2794—2796. 

Certain Lewis acids are known to induce an epoxide-aldehyde rearrangement <01TL8129>, and this chemistry has recently been combined in tandem with metal-mediated allylations. For example, epoxides react with tetraallyltin in the presence of bismuth(III) triflate to give homoallylic alcohols 116. The reaction involves an initial 1,2-shift to form an aldehyde 115, which is then attacked by the allyl tin species <03TL6501>. A similar but operationally more straightforward protocol is available by combining allyl bromide with indium metal, followed by the addition of epoxide <03TL2911>. 

Table 5.7 Bismuth(III)-triflate-promoted Fries rearrangement of naphthyl esters...

Catalytic quantities of bismuth(III) triflate initiate the rearrangement of epoxides to aldehydes which then react with (Z)-5-hydroxyalkenylsilanes to give 2,6-disubstituted 3,6-dihydro-277-pyrans (Scheme 58). ... 

BiCfr [34b] proved to be a better catalyst than scandium [76] or ytterbium triflates [77] for this rearrangement which is also catalyzed by Bronsted acids [78]. Other functionalities such as Boc, allyl, and propargyl are compatible with bismuth catalysis (Section 11.2.6). 

---