Migration at Boron Cage for Selective B–H Functionalization of <i>nido</i> ‐Carboranes

ABSTRACT Molecular rearrangement provides a powerful pathway to structurally unique and synthetically inaccessible molecules. To date, however, such transformations remain underdeveloped for boron clusters. Herein, we disclose a strategy for the selective functionalization of B–H bonds in nido ‐carboranes via an unprecedented migration at the boron cage. This process orchestrates a rearrangement of B–O substituted nido ‐carboranes upon reaction with diverse nucleophiles, including N‐heterocycles and thioethers, thus enabling the B–H functionalization at a position that is inaccessible through conventional methods. Its synthetic utility is demonstrated through facile post‐modification of drug molecules, synthesis of new boron delivery agents with 13 C labeling for boron neutron capture therapy (BNCT), and construction of carborane‐based luminogens that exhibit aggregation‐induced emission (AIE) and efficient reactive oxygen species (ROS) generation. Mechanistic investigations support a pathway involving nucleophile‐induced migration at the boron cage, facilitated by a high‐valent iodine reagent. This work establishes a paradigm for the B–H bond functionalization of boron clusters via migration at the boron cage, thereby expanding the synthetic toolbox for constructing functional molecules based on boron clusters.