Lanthanide‐Catalyzed Tandem Insertion of Secondary Amines with 2‐Alkynylbenzonitriles: Synthesis of Aminoisoindoles

A lanthanide‐catalyzed intermolecular hydroamination of 2‐alkynylbenzonitriles with secondary amines has been disclosed, providing a streamlined access to a range of aminoisoindoles in moderate to excellent yields. The salient features of this reaction include high bond‐formation efficiency, mild reaction conditions, 100 % atomic efficiency and good functional group tolerance. This methodology has also been successfully applied to the construction of other nitrogen‐containing compounds, such as 5 H‐imidazo[2,1‐a]isoindoles and isoquinolines. A plausible mechanism for the formation of aminoisoindoles involving initial N−H activation by a lanthanide complex followed by C≡N insertion into a Ln−N bond to form an amidinate lanthanide intermediate, which undergoes the cyclization is proposed. N−H Activation: A lanthanide‐catalyzed tandem hydroamination/cyclization reaction was developed for the construction of aminoisoindoles as well as other nitrogen‐containing compounds, such as 5H‐imidazo[2,1‐a]isoindoles and isoquinolines, in moderate to excellent yields. The salient features of this reaction include high bond‐formation efficiency, mild reaction conditions, 100 % atomic efficiency and good functional group tolerance.