Transition Metal‐Catalyzed C(sp2)‐H Bond Activation for 1,3‐Dienes Formations via Cross‐dehydrogenative Coupling

1,3‐Dienes are ubiquitous structural motifs in natural products, clinically relevant pharmaceuticals, functional luminescent materials, and pivotal organic building blocks, serving as indispensable synthons in modern organic synthesis. The development of efficient synthetic methodologies for 1,3‐dienes has consequently garnered significant attention, particularly transition metal‐catalyzed vinyl C(sp²)‐H cross‐dehydrogenation coupling (CDC), which has emerged as a highly attractive strategy due to its inherent atom‐ and step‐economy, along with hydrogen as the sole byproduct, thereby aligning with green chemistry principles. A central research objective in this field involves achieving precise control over the stereo‐ and site‐selective activation of C(sp²)‐H bonds, which critically determines reaction efficiency and product utility. This review systematically examines advancements over the past 15 years in transition metal‐catalyzed C(sp²)‐H functionalization for 1,3‐diene synthesis, with emphasis on comparative analyses of catalytic systems involving Pd, Rh, Ru, and other transition metals. Key reaction paradigms are comprehensively discussed, including terminal olefin homo‐coupling, cyclic olefin/terminal olefin cross‐coupling, macrocyclic conjugated olefin synthesis, and aromatic olefin/terminal olefin coupling.