ABSTRACT 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.
Saito et al. (Sun,) studied this question.