Ruthenium/N–Heterocyclic carbene-decorated covalent organic framework for N–H insertion cascade nucleophilic cyclization

Covalent organic frameworks have emerged as a powerful class of crystalline materials for transition-metal-catalysis and the development of new catalyst architectures on covalent organic frameworks is in high demand. Herein, we report the first example of a heterogenous ruthenium/N-heterocyclic carbene catalyst immobilized on covalent organic frameworks. This versatile Ru–NHC–COF platform enables N–H insertion cascade nucleophilic cyclization reactions, permitting efficient construction of benzoindole derivatives from readily accessible naphthylamines and diazo compounds in a single step. Peripheral functionalization of benzimidazolium N-heterocyclic carbenes enables facile access to Ru–NHC–COF. The catalyst shows broad substrate scope and excellent recyclability, which sets the stage for the synthesis of indole-based pharmaceuticals. Notably, this approach represents the first example of a heterogenous COF catalyst for N–H bond activation.