Evolution of Chiral N , N’ ‐Dioxide Ligands: from Rigidity to Flexibility

Comprehensive Summary Over the past two decades, the Feng group has built an extensive library of structurally diverse chiral N,N ′‐dioxides. As their skeletons evolved from rigid to flexible frameworks, these N,N ′‐dioxides exhibit high Lewis basicity, facile modifiability and outstanding coordination capacity. They serve as either catalysts or ligands in organocatalysis, Lewis acid catalysis, bimetallic catalysis, photocatalysis, radical chemistry and redox catalysis. Furthermore, the catalysts can form adaptive chiral pockets, mimicking enzymes that remodel their active sites to accommodate diverse substrates. They deliver outstanding performance in more than eighty classes of asymmetric transformations and have been applied to the synthesis of over fifty bioactive molecules. Their development follows a mutually beneficial cycle: reaction‐driven synthetic requirements promote catalyst optimization, and improved catalysts further advance asymmetric catalysis. This review outlines the evolution of Feng‐type catalysts: from rigid to flexible backbones, from structural mimicry to original innovation, from simple organocatalysts to powerful ligands, and from limited mechanistic knowledge to thorough mechanistic comprehension. Rather than presenting a comprehensive survey, this review enumerates pivotal milestones chronologically and underscores groundbreaking work that has spurred widespread follow‐up research. This story emphasizes gradual cumulative progress instead of sudden breakthroughs, aiming to stimulate more dedicated and rigorous fundamental investigations. Key Scientists