Synthesis of N-Heterocycles via Transition-Metal-Catalyzed Tandem Addition/Cyclization of a Nitrile

The diverse methodologies to synthesize N-heterocycles through transition-metal-catalyzed cascade addition/cyclization of a nitrile are discussed in this review. Aspects relating to three types of transition-metal-catalyzed addition of a nitrile with subsequent cyclization include (1) a transition-metal acting as a Lewis acid to accelerate the nucleophilic addition of a nitrile, (2) the late-transition-metal-catalyzed 1,2-insertion of a nitrile, and (3) an in situ generated radical by transition-metal catalysis to implement a radical addition/cyclization tandem reaction. Applications for the synthesis of natural alkaloids, their derivatives, and some bioactive compounds are also summarized herein. 1 Introduction 2 Nucleophilic Addition of a Nitrile Accelerated by a Lewis Acid 2.1 Late-Transition-Metal Catalysis 2.2 Early-Transition-Metal Catalysis 2.3 Lanthanide-Metal Catalysis 2.4 Cyclization from N-Arylnitriliums 3 Transition-Metal-Catalyzed Insertion of a Nitrile 4 Transition-Metal-Catalyzed Radical Addition of a Nitrile 5 Conclusions