C(sp3 )-H Arylation Promoted by a Heterogeneous Palladium-N-Heterocyclic Carbene Complex in Batch and Continuous Flow.

Abstract

A heterogeneous reusable palladium(II)‐bis(N‐heterocyclic carbene) catalyst was prepared and shown to catalyze the intramolecular C(sp3)−H activation/cyclization of N‐alkyl‐2‐bromoanilines furnishing indolines. This new catalytic system was based on a bis‐imidazolium ligand immobilized on a spaced cross‐linked polystyrene support. The iodide ligands on the catalyst played a central role in the efficiency of the process occurring through a “release and catch” mechanism. The heterogeneous nature of the catalyst was further exploited in the design of a continuous‐flow protocol that allowed a more efficient recovery and reuse of the catalyst, as well as a very fast and safe procedure.