En Route to Intermolecular Cross-Dehydrogenative Coupling Reactions.

Cross-coupling reaction between two C-H bonds has become a fundamental strategy in synthetic organic chemistry. With its increasing importance in green chemistry, atom economy, and step economy, its development has sky-rocketed within the last 20 years, with the term "cross-dehydrogenative coupling (CDC)" popularized and progressed by the group of Li and others to describe direct Y-Z bond formations from Y-H and Z-H bonds under oxidative conditions. Among all types of CDC reactions, the C-C bond formations are of prime importance in building up the molecular complexity but their categorization currently remains disarray due to a wide diversity, resulting in frequent display in separate topics. In this Perspective, a contemporary categorization via C-H activation strategies is presented herein, which could be vital for future CDC designs. With this mechanism-based categorization and discussion, we wish that this minireview will help more synthetic chemists gain insight into the design of CDC reactions and inspires more ideas on this topic.