Construction 7-membered ring via Ni–Al bimetal-enabled C–H cyclization for synthesis of tricyclic imidazoles

The construction of 7-membered ring via direct C7–H cyclization of benzoimidazoles with alkenes would provide a more atom- and step-economical route to tricyclic imidazoles and derivatives that widely exist in a broad range of bioactive molecules. However, transition metal-catalyzed C–H cyclization for medium-ring synthesis has been limited to reactive C–H bonds, instead, the activation of unreactive C–H bonds towards medium synthesis still remains an elusive challenge. Herein, we report a direct construction of 7-membered rings via Ni–Al co-catalyzed unreactive C7–H cyclization of benzoimidazoles with alkenes, providing a series of tricyclic imidazoles in 40–98% yield and with up to 95:5 er.

Construction 7-Membered Ring via Ni-Al Bimetal-Enabled C-H Cyclization for Synthesis of Tricyclic Imidazoles

The construction of 7-membered ring via direct C7−H cyclization of benzoimidazoles with alkenes would provide a more atom- and step economical route to tricyclic imidazoles and derivatives that widely exist in a broad range of bioactive molecules. However, transition metal-catalyzed C−H cyclization for medium-ring synthesis has been limited to reactive C−H bonds, instead, the activation of unreactive C−H bonds towards medium synthesis still remains an elusive challenge. Herein, we report a direct construction of 7-membered rings via Ni−Al co-catalyzed unreactive C7−H cyclization of benzoimidazoles with alkenes, providing a series of tricyclic imidazoles in 40−98% yield and with up to 95:5 er.

Recent Advances in the Development of Catalytic Methods that Construct Medium-Ring Lactams, Partially Saturated Benzazepines and Their Derivatives

Recent catalytic methods to construct medium-sized lactams­ and partially saturated benzazepines and their derivatives are surveyed. The review is divided into the following sections:1 Introduction2 Non-Transition-Metal-Catalyzed Reactions2.1 Beckmann Rearrangement2.2 Non-Beckmann Rearrangement Reactions2.3 Multicomponent reactions3 Transition-Metal-Catalyzed Reactions3.1 Gold-Catalyzed Reactions to Access Medium-Sized N-Hetero­cycles3.2 Reactions Involving a Metal η3-Complex Catalytic Intermediate3.3 Transition-Metal-Catalyzed Reactions of Strained Cycloalkanes4 Conclusions

Hydantoin-bridged medium ring scaffolds by migratory insertion of urea-tethered nitrile anions into aromatic C–N bonds

Bicyclic or tricyclic nitrogen-containing heterocyclic scaffolds were constructed rapidly by ring expanding intramolecular SNAr on a series of electronically unactivated heterocyclic precursors.

Recent advances in catalytic synthesis of medium-ring lactones and their derivatives

Medium-sized lactones are widely found in various natural products and pharmaceuticals. However, the efficient synthesis of these sturtures remains as a challenging topic in organic synthesis due to the disfavored...