Rhodium(III)‐Catalyzed Oxidative Annulation of Amidines with Alkynes via Sequential C−H Bond Activation

Recent approaches for the synthesis of heterocycles from amidines via a metal catalyzed C-H functionalization reaction

Transition metal catalyzed C-H bond activation has become one of the most important tools for constructing new chemical bonds. Introducing directing groups to the substrates is the key to a successful reaction, these directing groups can also be further transformed in the reaction. Amidines with their unique structure and reactivity are ideal substrates for transition metal-catalyzed C-H transformations. This review describes the major advances and mechanistic investigations of the C-H activation/annulation tandem reactions of amidines until early 2024, focusing on metal-catalyzed C-H activation of amidines with unsaturated compounds, such as alkynes, ketone, vinylene carbonate, cyclopropanols and their derivatives. Meanwhile this manuscript also explores the reaction of amidines with different carbene precursors, for example diazo compounds, azide, triazoles, pyriodotriazoles, and sulfoxonium ylides as well as their own C-H bond activation/cyclization reactions. A bright outlook is provided at the end of the manuscript.

Rhodium(III)-catalyzed oxidative annulation of N-arylbenzamidines with maleimides via dual C-H activation

An oxidative annulation of N-arylbenzimidamides with maleimides has been developed for the first time using a catalytic amount of the [Cp*RhCl₂]₂ complex for the synthesis of a diverse range of 1H-benzo[4,5]imidazo[2,1-a]pyrrolo[3,4-c]isoquinoline-1,3(2H)-dione derivatives. This method is versatile and atom-economical for producing polycyclic benzo[4,5]imidazo[2,1-a]pyrrolo[3,4-c] isoquinoline-1,3(2H)-dione scaffolds in a single step.

Micro-photo-flow reactor system for fused N-heteroaryl scaffold synthesis and late-stage functionalization of pyrazolopyridines

Late-stage functionalization (LSF) of active pharmaceutical ingredients can provide a straightforward approach to efficient de novo design and synthesis of drug molecules for structural activity relationship studies (SARS). Herein, we have developed a visible-light-driven modular micro-flow reactor consisting of an integrated post-synthetic work-up that was designed and developed to synthesize a fused N-heteroaryl scaffold and late-stage functionalization of pyrazolopyridines without using any expensive oxidant or additional photo-catalyst (PC).

Recent Advances in the Synthesis of Isoquinoline-Fused Benzimidazoles

This review includes recent developments in the synthesis of benzo[4,5]imidazo[2,1-a]isoquinolines with particular attention given to categorizing protocols based on the structural features of the ring architecture and crystallographically characterized reaction products.

Open-Air Dual-Diamination of Aromatic Aldehydes: Direct Synthesis of Azolo-Fused 1,3,5-Triazines Facilitated by Ammonium Iodide

A new and practical protocol for the synthesis of medicinally privileged azolo[1,3,5]triazines by simply heating under air has been presented. The in situ generated N-azolo amidines from commercially available aromatic aldehydes and 3-aminoazoles with ammonium iodide undergo the second diamination to accomplish the [3 + 1 + 1 + 1] heteroannulation reaction. This convenient process is appreciated by high efficiency, broad substrate scope, gram-scale synthesis, and operational simplicity under reagent-free conditions.