Iodine-mediated one-pot synthesis of indoles and 3-dimethylaminoindoles via annulation of enaminones

The synthesis of 2-carbonylindoles was achieved via a iodine-mediated cyclization of the corresponding enaminone precursors, which were formed by reaction of the alpha-arylaminomethylene carbonyl derivatives with N, N'-dimethylformamide dimethyl acetal (DMFDMA). An alternative and more efficient procedure consisted of a similar cyclization of the enaminones, but under solvent-free and grinding reaction conditions. In another iodine-promoted procedure, 2-carbonyl-3-dimethylaminoindoles were synthesized via a one-pot cascade reaction between the a-arylaminomethylene carbonyl derivative and DMFDMA.