Copper‐Catalyzed Substrate‐Controlled Assembly of 1,3,5‐Triazines From Aldehydes and Ammonium Acetate

A copper‐catalyzed assembly of symmetrical and unsymmetrical 1,3,5‐triazines directly from readily available aldehydes and ammonium acetate is reported. The use of ammonium acetate as a simple nitrogen source enables access to structurally diverse 2,4,6‐trisubstituted 1,3,5‐triazines without the need for prefunctionalized nitrogen‐containing building blocks. A broad range of aromatic, heteroaryl, fused‐ring, and metallocene‐derived aldehydes undergo the transformation under operationally simple conditions. Mechanistic studies suggest the involvement of radical intermediates and nitrile species in the triazine‐forming pathway. Interestingly, the reaction outcome is influenced by the nature of the aldehydic α‐carbon: whereas aldehydes lacking sufficient α‐hydrogens undergo the triazine‐forming cycloaromatization pathway, tested aldehydes bearing at least two α‐hydrogens follow an alternative pathway to afford 3,5‐disubstituted pyridines. The reaction is readily scalable and provides a practical approach to nitrogen‐rich heterocycles from simple aldehyde feedstocks.