Synthesis of Conjugated Materials Using Direct C-H Functionalization

Small molecules and polymers with conjugated structures are expected to serve as materials for organic electronic devices and are presently under development. These materials have traditionally been synthesized using cross-coupling reactions. In recent years, there have been developments in more straightforward synthesis methods for organic electronic device materials. These methods involve direct functionalization of C-H bonds, such as direct arylation, C-H/C-X coupling (where X is a halogen or pseudo-halogen), and cross dehydrogenation coupling, C-H/C-H cross-coupling. Although these methods are convenient for short-step synthesis, it is essential to achieve high C-H bond regioselectivity and suppress undesired homocoupling side reactions. This review presents pioneering examples of the synthesis of conjugated materials using two types of the direct C-H functionalization reactions and our recent research activities. In particular, we discuss the reaction mechanism that achieves high C-H bond regioselectivity and suppresses undesired homocoupling side reactions through the control of reductive elimination.