Pd-catalyzed reactions on pyridinium N-heteroarylaminides. Step-by-step synthesis of 3,5-unsymmetrically disubstituted 2-aminopyridines

Suzuki-Miyaura cross-coupling processes on N-pyridinium bromoazinyl aminides allow access to 3,5-disubstituted N-alkyl-2-aminopyridines. The synthetic pathway involves a regioselective bromination of pyridinium N-(pyridin-2-yl)aminide and a subsequent reaction with boronic acids to afford monosubstituted aminides in good yields. An additional bromination in the 5-position of the pyridine ring followed by a coupling reaction gives pyridinium N-(3,5-diarylpyridin-2-yl)aminides. Finally, a regioselective alkylation on the exo-nitrogen and reduction of the N-N bond yields highly substituted 2-aminopyridines.

The N-(pyridin-2-yl)pyridinium aminide allows, through two regioselective brominations followed by Suzuki-Miyaura cross-coupling processes together with a selective alkylation on the exo-nitrogen and reduction of the N-N bond, the access to 3,5-disubstituted N-alkyl-2-aminopyridines.