Direct Access to 9-Chloro-1<i>H</i>-benzo[<i>b</i>]furo[3,4-<i>e</i>]azepin-1-ones via Palladium(II)-Catalyzed Intramolecular <i>syn</i>-Oxypalladation/Olefin Insertion/sp²-C–H Bond Activation Cascade

Abstract

An efficient Pd(II)-catalyzed cascade approach was established for the synthesis of 9-chloro-1<i>H</i>-benzo[<i>b</i>]furo[3,4-<i>e</i>]azepin-1-ones starting from <i>N</i>-propargyl arylamines having a pendant α,β-unsaturated ester scaffold. The mechanism of this sequential process involved intramolecular <i>syn</i>-oxypalladation followed by olefin insertion and <i>ortho</i> sp²-C-Cl bond formation reactions. This high atom- and step-economical cascade sequence generated two heterocycle rings and three new bonds in a single synthetic operation.