Synthesis of 2-Acylindoles via Ag- and Cu-Catalyzed anti-Michael Hydroamination of β-(2-Aminophenyl)-α,β-ynones: Experimental Results and DFT Calculations

J Org Chem. 2018 Jun 15;83(12):6354-6362. doi: 10.1021/acs.joc.8b00508. Epub 2018 May 24.

Abstract

β-(2-Aminophenyl)-α,β-ynones afforded 3-unsubstituted 2-acylindoles in good yields in the presence of 20 mol % AgOTf under (microwave) MW heating. The use CuOTf as a 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, which 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 silver/copper catalysis. Density functional theory calculations on the Ag-catalyzed reaction revealed that the catalyst induces an electrostatic arrangement in the TS coherent with the experimentally observed cyclization.

Publication types

  • Research Support, Non-U.S. Gov't