Hydrogenative coupling of nitriles with diamines to benzimidazoles using lignin-derived Rh
2P catalyst.
iScience 2021;
24:103045. [PMID:
34585110 PMCID:
PMC8450259 DOI:
10.1016/j.isci.2021.103045]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Revised: 07/21/2021] [Accepted: 08/24/2021] [Indexed: 12/01/2022] Open
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.
Nitrile was developed as synthetic building block for organic synthesis
Reductive coupling of nitriles to 1,2-phenylenediamines yielded benzimidazoles
Strong P−Rh interaction and charge transfer to Rh enhanced Rh2P activity
H/D exchange between H2 and –CD3 in CD3CN occurred via intramolecular D-shift
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