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.
Synthesis of 2‑Acylindoles via Ag- and Cu-Catalyzed anti-Michael Hydroamination of β‑(2-Aminophenyl)-α,β-ynones: Experimental Results and DFT Calculations.
Navnath D. RodeMembro del Collaboration Group
;Issam AbdalghaniMembro del Collaboration Group
;Antonio ArcadiMembro del Collaboration Group
;Massimiliano AschiMembro del Collaboration Group
;Marco ChiariniMembro del Collaboration Group
;Fabio MarinelliWriting – Original Draft Preparation
2018-01-01
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.Pubblicazioni consigliate
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