Access to functionalized Mannich scaffolds via a calcium-catalyzed dehydrative aza-Friedel-Crafts reaction

The α-functionalization of amines and related scaffolds plays a key role in both target synthesis and medicinal chemistry. As such, elegant solutions employing transition metal catalysis, photoredox catalysis, and electrosynthetic methods have been described. The methods often rely on harsh activation conditions or difficult-to-access catalysts and experimental setups. Here, we report a calcium-catalyzed addition of aniline derivatives into N-acyliminium ions under mild conditions to access a diverse range of Mannich-type products. The reaction is unified and can be applied to N,O-acetal derivatives to access di-substituted amides and also isoindolinones as a method to functionalize medicinally relevant scaffolds. The reaction displays a high level of functional group tolerance and provides access to a diverse range of scaffolds.