Synthesis of 2,2’-Bipyridines through Catalytic C–C Bond Formations from C–H Bonds

The present review describes the homogenous catalytic methodologies for the synthesis of 2,2'-bipyridines involving C-C bond formation from C-H bond. There are three main approaches to build well-decorated 2,2'-bipyridines from C-H bond cleavage: i) the formation of C2-C2 ' bond by the dimerization of (activated) pyridines, ii) the C-H bond heteroarylation of activated pyridine, or iii) the late-stage functionalization of (activated) 2,2'-bipyridines including photoredox processes. Besides the scope and limitation of each methodologies, the relevant mechanisms of reaction are also discussed.