No abstract

Pyridine is a crucial heterocyclic scaffold that is widely found in organic chemistry, medicines, natural products, and functional materials. In spite of the discovery of several methods for the synthesis of functionalized pyridines or their integration into an organic molecule, new methodologies for the direct functionalization of pyridine scaffolds have been developed during the past two decades. In addition, transition-metal-catalyzed C–H functionalization and rare earth metal-catalyzed reactions have flourished over the past two decades in the development of functionalized organic molecules of concern. In this review, we discuss recent achievements in the transition-metal and rare earth metal-catalyzed C–H bond functionalization of pyridine and look into the mechanisms involved.

Chemodivergent reactions are more advantageous in organic synthesis that yield diversely functionalized scaffolds from common starting materials. Herein, we report an efficient metal-free chemodivergent protocol for the synthesis of 1-substituted 9H-pyrrolo[1,2-a]indole derivatives in the presence of catalytic amounts of Lewis acid/Brønsted acid conditions using 3-substituted indoles and β-trifluoromethyl-α,β-unsaturated ketones. Fine-tuning of the catalyst and solvent system in the reaction conditions deliver the trifluoromethyl, trifluoroethylcarboxylate, or carboxylic acid substituents on the C1-position of 9H-pyrrolo[1,2-a]indole derivatives in situ. It is postulated that the solvent and LA/BA catalyst interaction was found to be crucial for the catalytic C–F activation in these transformations.