Silver-Catalyzed Direct Synthesis of Trifluoromethylated Enaminopyridines and Isoquinolinones Employing Trifluorodiazoethane

This Letter reports a Ag-catalyzed
three-component approach for
the N-alkenylation of 2-aminopyridines employing aldehydes and trifluorodiazoethane.
Unlike the known reactions of trifluorodiazoethane with imines, which
generate Mannich adducts, aziridines, or triazolines depending on
the substrates and conditions, this reaction, after Mannich addition,
proceeds via a carbene formation and 1,2-aryl migration sequence to
afford (E)-enaminopyridines. This surprising selectivity,
which is effective for a wide range of aldehydes and 2-aminopyridines,
has been subsequently explored to access trifluoromethylated isoquinolinones.