Synthesis of 2,2’‐Bipyridines through Catalytic C−C Bond Formations from C−H Bonds

De Novo Synthesis of 2,2'-Bipyridines and Related Bis-azines via Cascade Coupling and Double Pyridannulation of Isocyanides

Herein, we present a new and general protocol for the assembly of 2,2'-bipyridyls from nonpyridine substrates without using any metal catalysts or organometallic reagents. The process starts from the coupling of two 1,3-dienyl isocyanides followed by a 6π-electrocyclization/aromatization cascade featuring the simultaneous formation of two pyridine rings in a single operation. Notably, this strategy is also applicable to the construction of nonsymmetrical 2-(2-pyridyl)-quinolines/-quinoxalines. Furthermore, the aggregation-induced emission (AIE) characteristics endow our approach with great potential in biorelevant fields.

Pyridine C(sp2)-H bond functionalization under transition-metal and rare earth metal catalysis

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.

A General, Multimetallic Cross-Ullmann Biheteroaryl Synthesis from Heteroaryl Halides and Heteroaryl Triflates

Despite their importance to medicine and materials science, the synthesis of biheteroaryls by cross-coupling remains challenging. We describe here a new, general approach to biheteroaryls: the Ni- and Pd-catalyzed multimetallic cross-Ullmann coupling of heteroaryl halides with triflates. An array of 5-membered, 6-membered, and fused heteroaryl bromides and chlorides, as well as aryl triflates derived from heterocyclic phenols, proved to be viable substrates in this reaction (62 examples, 63 ± 17% average yield). The generality of this approach to biheteroaryls was further demonstrated in 96-well plate format at 10 μmol scale. An array of 96 possible products provided >90% hit rate under a single set of conditions. Further, low-yielding combinations could be rapidly optimized with a single "Toolbox Plate" of ligands, additives, and reductants.