Plasma‐Mediated Selective Dinitrogen Fixation Into Primary Aniline

Direct CN bond formation using dinitrogen (N 2 ) constitutes an atom‐economical strategy for synthesizing N‐containing organics such as aniline, which, however, remains a challenge owing to the inherent inertness of both N 2 and aromatic CH bonds. Previous work has shown the plasma‐enabled efficient benzene amination from N 2 . Nevertheless, the amination products are nonselective, predominantly yielding diphenylamine rather than the synthetically more valuable primary anilines, and the underlying mechanism remains elusive. Herein, we demonstrate that selective CN coupling to primary anilines can be achieved by nitrogen plasma reacting with liquid or solution‐phase arenes, in the absence of any transition metal catalysts. For a series of multisubstituted alkylbenzene derivatives, the amination reaction proceeds selectively at the aromatic ring rather than the alkyl side chains, affording primary anilines with exclusive selectivity and yields exceeding 40% under optimized conditions. Combining product analysis and online mass spectrometric monitoring, we hypothesized that plasma promotes the generation of triplet arylnitrenium ions, and their rapid intramolecular hydrogen abstraction prevailing over intersystem crossing may serve as a key factor for the selective formation of primary anilines.