The intrinsic electrophilic feature for the terminal nitrogen of α-diazo-β-ketoesters/ketones has been elucidated by the intermolecular nucleophilic addition of two molecules of a dimethylsulfonium ylide. This methodology allows for access to highly functionalized hydrazones with a broad scope and good functional group tolerance. The reaction operates under simple and mild conditions without using a catalyst.

There has been a persistent impetus for the development of versatile C−H functionalization reactions, which represents a powerful approach to a wide variety of valuable chemical compounds. Transition metal catalyzed C−H functionalization has attracted intense interest and witnessed considerable advances in this field owing to its outstanding regioselectivity and atom‐economy. In recent years, rare‐earth (RE) metal‐based catalysts have been successfully employed in this flourished area, demonstrating unique selectivity and complementary reactivity with respect to late‐transition metal‐catalyzed C−H functionalization. The development of rare‐earth metal‐catalyzed C−H functionalization by taking the advantage of these characteristic properties is of great importance and interest. Herein, a panorama of rare‐earth metal‐catalyzed C−H functionalization during the last decade is presented.

The Cover Feature demonstrated all rare‐earth metal elements in the form of RE (abbreviation of rare‐earth) letters and a C−H bond was activated via rare‐earth metal catalysts and a C−R bond was consequently formed. In their Review, X. Xu and co‐workers provide a brief overview on rare‐earth metal‐catalyzed C−H functionalization reactions during the last decade. Transition metal catalyzed C−H functionalization has attracted great interest and witnessed considerable advances owing to its outstanding regioselectivity, step‐ and atom‐economy. In recent years, rare‐earth metal catalysts have exhibited unique reactivity and selectivity in C−H functionalization, making it an important complement for late‐transition metal‐catalyzed C−H functionalization. More information can be found in the Review by X. Xu and co‐workers.

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C−H borylation strategy has spurred intense research endeavors due to the high atom- and step-economy it represents and the broad utilities of the resulting organoboranes. Nevertheless, this powerful transformation has subjected to limited substrate scope and poor regioselectivity when it was applied to Lewis basic substrates (e.g., azines). The basic functionalities in substrates would coordinate to the metal centers, hindering the formation of products. Herein, we provide a brief overview of recent advances in transition-metal-catalyzed regioselective C−H borylation of pyridines. Moreover, attentions are paid to the latest contributions presenting remarkable regioselectivity.