Magnesium‐Promoted Benzidine‐Type Rearrangement for Regioselective Construction of Polyfunctionalized Biaryls

A magnesium‐promoted benzidine‐type rearrangement of 1,3‐dihalonitroarenes with aryl Grignard reagents has been developed, enabling the highly regioselective and efficient synthesis of 1‐amino‐1’‐hydroxy‐4,4’‐biaryls under simple, transition‐metal‐free conditions. A rational substrate design—featuring an ortho substituent (R) and two meta ‐substituted electron‐withdrawing groups (X, Y)—steers the reaction trajectory, converting a previously minor [5,5]‐sigmatropic migration into the dominant pathway. The transformation exhibits broad functional‐group tolerance, excellent scalability, and provides direct and operationally straightforward access to polyfunctionalized biaryls. Furthermore, trifluoroacetamide‐substituted nitroarenes undergo [5,5]‐rearrangement followed by intramolecular cyclization to furnish CF 3 ‐substituted benzimidazoles with high regioselectivity. Overall, this study expands the conceptual scope of benzidine‐type rearrangements and establishes a mechanistically tunable, sustainable strategy for constructing valuable biaryl and heteroaromatic scaffolds.