A ligand-free, copper-catalyzed cascade sequence to indole-2-carboxylic esters

A variety of indole-2-carboxylic esters are accessible in yields up to 61% through a ligand-free, copper-catalyzed reaction of a series of commercially available 2-halo aryl aldehydes with benign glycine amidoesters, including the common reagent ethyl acetamidoacetate. This one-pot, three-reaction format allows ready entry to the desired heterocycles from starting substrates in the reactivity order of iodo > bromo ⩾ chloro substituents. An assortment of functional groups is tolerated, adding to the generality of this methodology.