Halides indium triflate

Scheme 8.6 Reactivity patterns of monovalent indium triflate (a) and halide (b) salts and their crown ether complexes (X = Cl, Br, I R = H, Cl). With permission from Ref [88],...

Indium-mediated allylation of an unreactive halide with an aldehyde132 was used to synthesize an advanced intermediate in the synthesis of antillatoxin,133 a marine cyanobacteria (Lyngbya majus-cula) that is one of the most ichthyotoxic compounds isolated from a marine plant to date. In the presence of a lanthanide triflate, the indium-mediated allylation of Z-2-bromocrotyl chloride and aldehyde in saturated NH4C1 under sonication yielded the desired advanced intermediate as a 1 1 mixture of diastereomers in 70% yield. Loh et al.134 then changed the halide compound to methyl (Z)-2-(bromomethyl)-2-butenoate and coupled it with aldehyde under the same conditions to yield the desired homoallylic alcohol in 80% yield with a high 93 7 syn anti selectivity (Eq. 8.55). 

Of interest also is the aqueous Reformatsky cross-coupling reaction between a-halo ketones or aldehydes and carbonyl compounds in the presence of zinc, tin and indium. Like the Barbier-type reactions, indium was found to be the most efficient metal and it strongly reduced undesirable side reactions such as the reduction of the halide [134]. As usual in aqueous reactions implicating carbonyl compounds, lanthanum(III) triflate promoted the reaction [146]. 

C5Mes)In is with CF3SO3H which gives the triflate salt of In ". The salt ln[02SCF3] is air-sensitive and hygroscopic but is, nonetheless, a convenient source of indium(I) as an alternative to ln(I) halides. 

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