Bismuth triflate catalysis

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. 

The benzoylation of both activated and deactivated aromatic compounds with benzoic acids (BACs) is achieved by using bismuth triflate (10% mol) in the presence of TFAA or heptafluorobutyric anhydride (HFBA).27 meffl-Xylene undergoes acetylation with 100% yield by using acetic acid (AAC) in the presence of TFAA under bismuth or scandium triflate catalysis (10% mol). The bismuth-triflate-catalyzed reaction can be extended to different aromatics as well as to aliphatic and aromatic carboxylic acids, giving ketones in nearly quantitative yield. Benzene and chlorobenzene are benzoylated with a BAC/HFBA mixture in the presence of bismuth triflate (10% mol), giving the corresponding BPs in 90%... 

Epoxides can also be converted to 1,3-dioxolanes by treatment with acetone in the presence of catalytic amounts of bismuth(lll) salts, with yields ranging from 87-99%. For example, the epoxy allyl ether 98 provided the dioxolane 99 in 97% yield using bismuth triflate as the catalyst <01SC3411>. When simple epoxides are treated with Aw(triphenylphosphine)-iminium cobalt tetracarbonyl (PPN-Co(CO)4) under Lewis acid catalysis, a carbonyl insertion reaction provides p-lactones regioselectively in good to high yields. The carbonylation occurs selectively at the unsubstituted position, and the reaction is... 

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). 

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