Synthetic and mechanistic studies of indium-mediated allylation of imines in ionic liquids.

Aldimines derived from aryl and non-enolizable aliphatic aldehydes were allylated with allyl bromide mediated by indium powder in [bpy][BF4] (bpy = N-butylpyridine) to give good yields of the corresponding homoallylic amines. Selective formation of monoallylated amines can be achieved by varying the amount of bromide ion additive in the form of [bpy][Br]. The transient organoindium intermediates, allylindium(I) and allylindium(III) dibromide formed in the reaction, were studied by NMR spectroscopy to explain the selectivity.