Hydrogenative coupling of nitriles with diamines to benzimidazoles using lignin-derived Rh₂P catalyst.

ABSTRACT: Nitrile (C≡N bond) activation for direct organic synthesis has been less explored so far due to a high redox potential of nitrile and its low dissociation energy of C-CN bond. Herein, we demonstrate a direct reductive coupling of nitriles and 1,2-phenylenediamines to yield various benzimidazoles in excellent yields (95%-99%) by using rhodium phosphide (Rh₂P) catalyst supported on lignin-derived carbon (LC) using H₂ (or hydrazine hydrate) as a hydrogen source. The high catalytic performance of Rh₂P/LC is attributed to enhanced charge transfer to Rh and strong P-Rh interactions. Our isotope trace experiment confirms the presence of H/D exchange between H₂ and the inert -CD₃ group of CD₃CN via an intramolecular D-shift. Reusability of Rh₂P/LC is further demonstrated by a seven-time recycling without evident loss of activity. This research thus highlights a great potential in organic transformation with nitrile as a synthetic building block.

SUBMITTER: Zhang J 

PROVIDER: S-EPMC8450259 | biostudies-literature | 2021 Sep

REPOSITORIES: biostudies-literature