Desulfurdioxidative N‐N Coupling of N‐Arylhydroxylamines and N‐Sulfinylanilines: Reaction Development and Mechanism

A highly efficient and chemoselective approach for the divergent assembling of unsymmetrical hydrazines through an unprecedented intermolecular desulfurdioxidative N−N coupling is developed. This metal free protocol employs readily accessible N‐arylhydroxylamines and N‐sulfinylanilines to provide highly valuable hydrazine products with good reaction yields and excellent functional group tolerance under simple conditions. Computational studies suggest that the in situ generated O‐sulfenylated arylhydroxylamine intermediate undergoes a retro‐[2π+2σ] cycloaddition via a stepwise diradical mechanism to form the N−N bond and release SO2. This article describes a novel and practical strategy for N−N bond construction. The strategy involves an unprecedented intermolecular cascade O‐sulfination and desulfurdioxidative N−N coupling (via stepwise retro‐[2π+2σ] cycloaddition, supported by quantum chemistry calculations) from readily available N‐arylhydroxylamines and N‐sulfinylanilines under metal and oxidant free conditions.