Mechanochemical Activation Switches the Chemoselectivity of the Suzuki–Miyaura Cross‐Coupling to Give Azobenzenes

The palladium-catalyzed Suzuki-Miyaura cross-coupling reaction is considered as a crucial technique in the field of organic chemistry. Traditionally, the reaction between aryl diazonium salts and arylboronic acids in solution predominantly facilitates carbon-carbon (C─C) bond formation. However, our research reveals that mechanochemical techniques can shift the chemical selectivity in Suzuki-Miyaura cross-coupling, resulting in the generation of non-symmetric azobenzene compounds under neat milling conditions. Azobenzenes have progressed from being merely textile dyes to multifunctional molecular systems critical for advanced technologies; however, the synthetic challenges associated with non-symmetric azo derivatives remain significant. Here, we present an innovative methodology that eliminates the use of conventional solvents while demonstrating exceptional substrate compatibility and short reaction time under ambient conditions. Detailed mechanistic investigations suggest that mechanochemical conditions alter the reaction pathway by selectively promoting carbon-nitrogen (C─N) coupling.