Synthesis of 2-acylindoles via Ag- and Cu-catalyzed anti-Michael hydroamination of β-(2-aminophenyl)-α,β-ynones: Experimental results and DFT calculation

β-2-aminophenyl)-α,β-ynones afforded 3-unsubstituted 2-acylindoles in good yields in the presence of 20 mol% of AgOTf under MW heating. The use CuOTf as catalyst resulted in a similar reaction outcome, generally with a lower efficiency. This transformation represents the first example of 5-endo-dig cyclization of 2-alkynylanilines bearing an acyl group linked to the triple bond. By contrast with the previously reported gold-catalyzed reaction of β-2-aminophenyl)-α,β-ynones, that resulted in the formation of dibenzo[1,5]diazocines through a sequential process triggered by an intermolecular hydroamination, a selective intramolecular anti-Michael hydroamination was observed in the present study by mean of silver/copper catalysis. Density Functional Theory calculation on the Ag-catalyzed reaction revealed that the catalyst induces an electrostatic arrangement in the TS coherent with the experimentally observed cyclization.