Metal‐free Transformations of Nitrogen‐Oxyanions to Ammonia via Oxoammonium Salt

Transformations of nitrogen‐oxyanions (NO x − ) to ammonia impart pivotal roles in sustainable biogeochemical processes. While metal‐mediated reductions of NO x − are relatively well known, this report illustrates proton‐assisted transformations of NO x − anions in the presence of electron‐rich aromatics such as 1,3,5‐trimethoxybenzene (TMB−H, 1 a ) leading to the formation of diaryl oxoammonium salt [(TMB) 2 N + =O][NO 3 − ] ( 2 a ) via the intermediacy of nitrosonium cation (NO + ). Detailed characterizations including UV/Vis, multinuclear NMR, FT‐IR, HRMS, X‐ray analyses on a set of closely related metastable diaryl oxoammonium [Ar 2 N + =O] species disclose unambiguous structural and spectroscopic signatures. Oxoammonium salt 2 a exhibits 2 e − oxidative reactivity in the presence of oxidizable substrates such as benzylamine, thiol, and ferrocene. Intriguingly, reaction of 2 a with water affords ammonia. Perhaps of broader significance, this work reveals a new metal‐free route germane to the conversion of NO x  to NH 3 .